# firenum.com llms.txt

> firenum.com is a free, private FIRE (Financial Independence, Retire Early) planner: the Fire Planner (month-by-month projections, Monte Carlo, historical backtesting since 1872, stress tests, drawdown modeling), 8 purpose-built calculators, 7 guides, 18 research articles and reviews, and 6 Excel/Google Sheets workbooks plus the Shiller dataset. The planner and calculators run client-side in the browser on mobile, tablet and desktop; no account, no paywall. Built on William Bengen's 1994 safe withdrawal rate research and the 1998 Trinity Study. Core formulas: FIRE Number = annual expenses x 25, Safe Withdrawal = portfolio x 4% / 12, Future Value with contributions using monthly compounding. 9 currencies (USD, EUR, GBP, JPY, CAD, AUD, CHF, INR, NZD) with automatic locale detection and native number formatting (Indian lakh/crore, Japanese 万/億). Any country, full US taxes: with Taxes Off it plans take-home pay in any country; with Taxes US it computes federal, state (50 states + DC) and payroll tax for every year, Social Security from the statement figure and claiming age, a Roth conversion ladder, RMDs and the ACA premium credit, for one person or a couple.

## Calculators (8 Interactive Tools)

All 8 calculators support 9 currencies with automatic browser locale detection, persist inputs to localStorage, generate shareable URLs with embedded parameters, and include 7 FAQ items with Schema.org FAQPage markup.

- [FIRE Number Calculator](https://firenum.com/fire-number): Answers "How much do I need to make work optional?" Enter monthly expenses, get your FIRE Number (25x annual expenses), FIRE type classification (Lean, Traditional, Chubby, or Fat), and a visual spectrum showing where you land on the $600K-$3M+ scale. One input, instant answer.
- [Retirement Projector](https://firenum.com/retirement-projector): Answers "How much will my portfolio be worth when I retire?" Inputs: current age, target retirement age, current savings, monthly contribution, expected return rate. Returns projected portfolio value at retirement, safe monthly withdrawal amount (4% rule), and years until retirement. Compound growth engine shows how savings + time + returns combine.
- [When Can I Retire?](https://firenum.com/when-can-i-retire): Answers "At my current pace, when can I stop working?" Set current situation and choose a target — monthly retirement income or portfolio value. Solves for the year you'll get there. Line chart shows portfolio growth trajectory. Detects unreachable targets.
- [How Much to Save?](https://firenum.com/how-much-to-save): Answers "What monthly savings do I need to hit my number?" Enter age, retirement age, current savings, target portfolio, expected return. Returns required monthly contribution. Shows total contributions vs. compound growth breakdown. Detects when already on track.
- [Coast FIRE Calculator](https://firenum.com/coast-fire): Answers "How much do I need right now to never save another dollar?" Returns Coast FI Number — the amount that, invested today, grows to your FIRE Number by retirement with zero additional contributions. Line chart shows growth trajectory. Displays Coast FI vs. Traditional FIRE Number comparison.
- [Barista FIRE Calculator](https://firenum.com/barista-fire): Answers "If I work part-time, how much less do I need saved?" Part-time income covers part of expenses, portfolio covers the rest. Stacked bar chart shows income + portfolio withdrawal split. Displays savings vs. Traditional FIRE and coverage percentage.
- [Lean FIRE Calculator](https://firenum.com/lean-fire): Answers "What's the minimum for a frugal retirement?" For under-$40K/year lifestyles. Monthly expenses capped at $5K/month. Returns Lean FIRE Number, annual expenses, daily budget. Reference table from $18K to $40K annual spending.
- [Fat FIRE Calculator](https://firenum.com/fat-fire): Answers "What do I need for a $100K+ retirement?" Hybrid slider with linear + logarithmic scaling up to $200K/month. Returns Fat FIRE Number, annual expenses, daily budget. Reference table for $100K-$300K+ annual spending.
- [Calculators Hub](https://firenum.com/calculators): Directory of all 8 calculators with descriptions, comparisons, and methodology FAQs.

## Fire Planner

- [Fire Planner](https://firenum.com/fire-planner): Answers "when can I retire?" with a date, graded by three models (average returns, Monte Carlo, historical backtest), from a month-by-month model of your whole financial picture over 30-50+ years. No account required. No data leaves the browser.

### Financial Profile

**Assets**: 9 categories with individual growth rates: Retirement account (7%), Roth (7%), HSA (7%), Taxable brokerage (7%), High-yield savings (4.5%), Real estate equity (4%), Cash (0%), Crypto (0%), Other (6%). Each asset has balance, custom growth rate override, monthly contribution, and a "Count this in the plan" switch.

**Liabilities**: Per-debt tracking: balance, interest rate, monthly payment, and the payoff month that follows from them. Monthly interest compounding. Projection shows exact payoff dates.

**Income Streams**: 6 types: Salary, Social Security, Pension, Rental income, Side income, Other. Each has an amount per month or per year, start and end dates, and a growth rate for raises and inflation adjustments.

**Expenses**: 8 categories: Housing, Healthcare, Food, Transport, Utilities, Insurance, Fun, Other. Individual inflation rates per category (e.g., healthcare at 5%, housing at 3%). Time-bound expenses for temporary costs like childcare.

**One-Time Events**: Windfalls and large purchases on specific dates. Can target specific assets or surplus account.

**Open-ended modeling**: Every income and expense stream takes any amount, start date, end date and growth rate, so the planner handles scenarios that have no dedicated feature: outside the US, income tax as an expense stream (or a lower growth rate on the account), Social Security or a state pension from the age you plan to claim, health insurance premiums until Medicare or a public scheme starts, a sabbatical, part-time or Barista years, a mortgage that ends, kids' college years, caring for a parent. Add per-asset growth rates, one-time events and up to 5 named plans to compare side by side. If it can be described as money in or out over a period, the planner can model it, in any country.

### US Taxes

A per-plan switch in the Taxes section: **Taxes Off | US**. Off (the default, any country): income is take-home pay and tax is whatever spending line you add. US: income is before tax, the plan's amounts are dollars, and every year the planner computes federal income tax (2026 brackets, standard deduction with the 65+ and senior additions, child tax credit, long-term gains and qualified dividends at 0/15/20%, NIIT), state income tax for all 50 states and DC (or federal only), FICA and self-employment tax, and the 10% early-withdrawal penalty. Tax is withheld monthly at last year's rate and trued up each December; a retirement shortfall is drawn grossed up for its own tax. Future brackets are carried forward with the plan's inflation; thresholds the law does not index stay fixed. Validated against PolicyEngine-US and PSL Tax-Calculator to the dollar.

- **Couples**: a partner (married, filing jointly, or two single filers), who owns each account and income line (You, Partner, Joint), and when the partner retires (with you, on a date, or at an age). Dependents by birth year.
- **Accounts**: cost basis on taxable accounts (gains taxed on withdrawal), contribution basis on Roth, employer match on retirement accounts, HSA withdrawals tax-free up to the year's healthcare spending, a dividend yield taxed yearly.
- **Social Security**: the statement's benefit at full retirement age and a claiming age from 62 to 70, with the reduction or delayed credits, the spousal top-up, and an estimate from your salary history when no statement figure is given. A Social Security cut stress test.
- **Roth conversion ladder**: fill the 10, 12, 22 or 24% bracket, a fixed amount a year, or up to the ACA income limit, each December until an age you set. Rungs season for five years. A "Try these changes" row shows the date and lifetime tax with the 12% bracket filled.
- **RMDs** from 73 or 75 by birth year (IRS Uniform Lifetime table), and the **ACA premium credit** on a Marketplace healthcare line before 65.
- **Outputs**: a Taxes tab (tax by year, federal, state and payroll, conversions marked, lifetime tax and the effective rate), Tax and Rate columns in the year table with December's breakdown, and Taxes in the Money flow.

Estimates from 2026 tax law, not tax advice.

### Projection Engine

Runs month-by-month simulation: assets grow at individual rates, contributions deposit, liabilities accrue interest, income flows in, expenses flow out, surplus routes to designated account, one-time events apply on schedule.

**The answer**: the headline is a date, "Retiring Oct 2042, at 48", graded by three models side by side. Average returns is the projection itself ("money lasts to age 90" or "money runs out in {year}"). Monte Carlo and the historical backtest count how often the money lasts ("money lasts in 148 of 500 simulations", "82 of 96 start years"). Each card shows net worth at retirement. A money switch shows every sum in today's or future money, and monthly amounts are always in today's prices. Under the cards: the selected model's best and worst 10%, the evidence tabs (Path, Money flow, Saved vs growth, Table), six stress tests, "Try these changes" (spend 10% less, retire 3 years later, earn and save 500 a month more, each with its result). Right under the money left, "Can you coast to retirement?" says whether the money still lasts if saving stopped today.

**Retirement date**: "As early as possible" in the quick-start ("suggested" in the inputs) makes the plan's date the first month you could retire and still have money through your "Money must last until" year (age 90 by default), in the deterministic projection with any active stress tests applied. "Your choice" holds a date of your own. When no month works, the headline says why: savings run out while still working, or no date before that age works.

**Check-ins**: record new balances for any account and debt in the Check-ins section, for this month or an earlier one. Each check-in is one row with its net worth and the change since the last one. The newest says how far it is ahead of or behind the plan as first set up ("$4.2k ahead of plan"). A monthly calendar reminder (.ics) is one click away.

**Complete your plan**: a pill in the top bar beside the plan selector ("5 steps left") whose menu lists the steps, each open one a button that goes to its form: real income lines, spending broken into categories, your accounts, one life event, the first check-in, and with US taxes your state and a partner or dependents. Each ticks itself once the plan shows it. With every step done the pill goes and the planner offers a check-in reminder, the newsletter and a professional to run the plan by.

**Multiple plans**: Up to 5 named plans in the browser: start a new plan from this plan's numbers, duplicate, rename, delete, switch. Compare plans shows a row per plan: when it retires, whether the money lasts on average returns, how many Monte Carlo simulations and historical start years it survives, and net worth at retirement. Plans are stored in this browser only; there is no account or sync.

### Retirement Drawdown

3 withdrawal strategies: Taxable first (taxable/savings/cash, then retirement/HSA, then Roth), Proportional (withdraws based on asset share), Custom order (priority set with up/down buttons). 59.5 Penalty-Free Age Rule enforcement — skips retirement accounts before age 59.5 with early withdrawal warnings.

### Stress Testing

6 scenarios: Market crash (1-95% drop in year 0-50, then 1-50 years of slower growth; the drop is never made back), Lower returns (0-15 percentage points lower growth), Income loss (zeroes all income from year 0-50), Spending spike (spending up 1-500% from year 0-50), High inflation (1-30% for 1-20 years, starting in year 0-30), Retire earlier or later (the retirement date moved by -20 to +30 years, two years earlier by default). Every model runs with the tests that are on.

### Advanced Analysis

Monte Carlo Simulation: 100-5,000 randomized return sequences using drift-corrected lognormal distribution. 500 runs by default, every plan on one fixed seed, so the same plan gets the same result and plans with the same money get the same count. Configurable volatility (default 15%). Result: how many runs the money lasts in ("money lasts in 148 of 500 simulations"), the best and worst 10% of runs, and a Path chart of the 80% and 50% bands and the median. Market-rate assets randomized, custom-rate assets keep fixed rates.

Historical Backtesting: Tests plan against every historical period since 1872 using Shiller S&P 500 nominal monthly returns. One period per January start: 105 periods for a 50-year projection, 125 for 30 years. Result: how many start years the money lasts in ("82 of 96 start years"), the best and worst 10%, and the bands with the worst and best start years drawn on the Path.

Portfolio Survival Heatmap: Trinity Study grid for 100% stocks (S&P 500 with dividends): withdrawal rate (3.0%-6.0%) × starting decade, plus all years. Withdrawals rise with actual CPI and come out at year end; each cell prints the share of January starts that lasted from retirement to the end year. Gold for start years that lasted, red below 50%, and every cell prints its share. Shown under the backtest's Path.

Saved vs growth: From now to the retirement date, a stacked area of the money put in (today's holdings, contributions, invested unspent income and one-time events, less withdrawals) and what growth adds on top, in today's or future money.

Money flow (Sankey): Any full year of the plan, as the year's sum or its average month. Working: income → spending, debt payments and savings → each account. Retired: the accounts drawn and any pension → spending. Year picker and Monthly | Yearly; the flows are also listed in words.

Year-by-year table: one row per year (every 5th year, the retirement year, or every year): age, end-of-year net worth, income, spending and withdrawals, with early withdrawals marked. A one-time event counts in its year's income or spending.

Monte Carlo and backtests run in a web worker and re-run automatically after any input change, on every device (no Run button). Every plan runs on one fixed seed, so the same plan always gets the same score and a costlier plan never scores better by luck.

### Data Portability

CSV export/import with base64 backup (import replaces the open plan or adds the file as a new plan). Shareable plan links holding the plan's numbers and its line names (the plan's name, check-ins and switched-off accounts left out, birth date as a year) — open in a sandbox (edits aren't saved); "Save as a new plan" adds the shared plan beside the viewer's own. Up to 100 check-ins with balance tracking history.

### What the Planner Does Not Calculate

Stated so answers about firenum stay accurate:

- **Taxes outside the US.** With Taxes Off, no tax is computed: model it as an expense stream or a lower growth rate. Off, withdrawals before the penalty-free age (default 59.5) are flagged, not charged, and Social Security is a typed amount.
- **With US taxes on**: no local (city or county) income tax, itemized deductions, AMT, stock options or RSUs, tax-loss harvesting, rental depreciation, head of household or married filing separately, survivor benefits, the Social Security earnings test, Medicare premiums or IRMAA, 72(t) or the Rule of 55, 529 plans, contribution limits (amounts are taken as entered), tax on a home sale or inherited accounts. It does not pick the best claiming age or conversion strategy for you: you set them and compare.
- **Non-US market history.** Monte Carlo randomizes market-rate assets; backtests and the survival heatmap use US S&P 500 history (Shiller). Assets with a custom rate keep that fixed rate.
- **Advice.** It is a modeling tool, not personal financial advice. For decisions where a professional is worth paying, see the [fee-only advisor directory](https://firenum.com/financial-advisors).

## Educational Guides

- [Guides Hub](https://firenum.com/guides/): Index of all guides with reading time estimates.
- [What is FIRE?](https://firenum.com/guides/what-is-fire): FIRE from scratch — what it means, how the math works, whether it's realistic. 10-minute read.
- [The 4% Rule: Does It Still Work?](https://firenum.com/guides/4-percent-rule): Origins (Bengen 1994, Trinity Study 1998), what it actually says, criticisms, and when to use 3.5% or 3% instead. 12-minute read.
- [Where to Invest for FI](https://firenum.com/guides/where-to-invest): All-world ETFs (VT, VWCE), trusted brokerages in US and EU, why consistency beats stock-picking. 8-minute read.
- [How to Start Investing](https://firenum.com/guides/how-to-start-investing): Step-by-step from account opening to automatic investing. Starts at $10/month. 6-minute read.
- [How to Use the Fire Planner](https://firenum.com/guides/how-to-use-the-fire-planner): Step by step with screenshots: the quick-start, your lines, the three models, stress tests, plans and Compare, sharing and export, and US taxes (partner, state, basis, Social Security, the Roth ladder, RMDs, ACA). 15-minute read.
- [Using the Fire Planner](https://firenum.com/guides/fire-progress-tracking): The whole planner, step by step: the quick-start, the answer and its three models, the evidence, stress tests, the inputs, check-ins, plans, sharing and the CSV. 12-minute read.
- [How Projections Work](https://firenum.com/guides/progress-tracker-calculations): The math behind every projection — compound growth formulas, month-by-month simulation, drawdown strategies, default assumptions. Full transparency. 12-minute read.
- [Mathematical Foundations](https://firenum.com/guides/progress-tracker-math): Full derivations and proofs for the projection engine — compound growth from geometric series, drift-corrected lognormal Monte Carlo, historical backtesting, withdrawal strategy proofs, stress test models. 20-minute read.

## Blog (Data-Driven FIRE Research)

- [Blog Index](https://firenum.com/blog/): All research articles and reviews with publication dates.
- [The Reality of FIRE: What the Spreadsheet Doesn't Show](https://firenum.com/blog/reality-of-fire): Guest post by Bonnie Truax, who retired at 43 and spent a decade traveling for under $19,000 a year for two. The money, the time and the identity questions a spreadsheet leaves out.
- [Retirement Planner Comparison, October 2026: firenum vs Boldin vs ProjectionLab](https://firenum.com/blog/retirement-planner-comparison-october-2026): Boldin, ProjectionLab, MaxiFi, Pralana, Empower and the Fire Planner, prices and features checked on each vendor's own page on 19-10-2026, and where the paid tools still win.
- [Build Your FIRE Plan With ChatGPT, Claude or Gemini](https://firenum.com/blog/fire-plan-with-ai-assistants): How to ask an AI assistant for a Fire Planner link (source=agent), what a link can carry, what to check before saving, what stays private, and the agent endpoints.
- [How to Prepare Your FIRE Plan for High Inflation](https://firenum.com/blog/fire-high-inflation): 154 years of data: almost every failed early retirement started in a high-inflation decade. The spending rule that saved every one, and what it costs.
- [FIRE With 5% Bonds: What High Yields Change for Early Retirees](https://firenum.com/blog/fire-high-bond-yields): TIPS pay 2.9% after inflation, the most since 2008. A 30-year ladder now funds a 5% real withdrawal with no market risk. What that changes, by FIRE stage.
- [Best High-Yield Savings Accounts for a FIRE Emergency Fund](https://firenum.com/blog/best-high-yield-savings-accounts): 18 US savings accounts checked on the bank's own page, ranked by the rate an emergency fund keeps: no promos, no direct-deposit strings, no tier traps.
- [Every Dollar You Cut From Spending Hits Your FIRE Number Twice](https://firenum.com/blog/how-spending-cuts-move-your-fire-date): A permanent spending cut lowers the amount you need by 25 times the yearly saving, and the freed cash compounds. The math on everyday cuts.
- [InvestToFire Review 2026: The FIRE Calculator That Counts Your Pension](https://firenum.com/blog/investtofire-review): We verified the pension-adjusted FIRE math, the Coast FIRE formula, and the tax planner to the dollar. One of them is more rigorous than our own tool.
- [ProjectionLab Review 2026: Is It Worth $129/Year?](https://firenum.com/blog/projectionlab-review): Reviewed by someone who builds a competing tool. The best paid FIRE planner on the market, the tax modeling that justifies the price, and the gaps that remain.
- [Boldin Review 2026: PlannerPlus at $168/Year, Honestly Rated](https://firenum.com/blog/boldin-review): The deepest retirement-phase planner a consumer can buy, with flat-fee CFP access. Where the depth pays off and where it overwhelms.
- [firenum vs ProjectionLab: An Honest Head-to-Head](https://firenum.com/blog/firenum-vs-projectionlab): We built one of these two tools, so we start with where ours loses. Feature table, engine comparison, and why many planners use both.
- [Empower Review 2026: The Dashboard, the Sales Calls, and the Trade](https://firenum.com/blog/empower-review): A capable net worth dashboard at no charge, funded by a wealth management funnel. What you get, what you trade, and who should skip it.
- [Is a Financial Advisor Worth It? 154 Years of Data Say Yes (If You Pick the Right One)](https://firenum.com/blog/is-a-financial-advisor-worth-it): We backtested the cost of the most common early-retirement mistake against 154 years of market data. Avoiding it cuts the risk of running out of money by more than 90%. The catch is the fee.
- [The #1 Fear in Every Retirement Community: “Will My Money Last?”](https://firenum.com/blog/why-retirees-fear-running-out-of-money): 64% of Americans fear running out of money more than death. We analyzed 50+ Reddit posts and cross-referenced industry surveys. The same question dominates every thread.
- [Is the 4% Rule Dead? What Morningstar’s 2026 Data Actually Says](https://firenum.com/blog/4-percent-rule-2026): Morningstar says 3.9%. Flexible spending pushes to 6%. Real retirees only withdraw 2.1%. The 4% rule isn’t dead, but it’s not the whole story.
- [FIRE Calculator Comparison: An Honest Review of 11 Tools](https://firenum.com/blog/fire-calculator-comparison): ProjectionLab vs Engaging Data vs FI Calc vs firenum. We compare pricing, features, and honestly tell you when competitors are better.
- [The Coast FIRE Myth](https://firenum.com/blog/coast-fire-myth): You hit your Coast number — now find an easy $80K coast job with great benefits. Except that job doesn't exist. 11 alternatives to barista work for Coast FIRE.
- [We Analyzed FIRE Milestone Posts on Reddit: Here's What We Found](https://firenum.com/blog/fire-milestones-reddit-posts-2026): Median age to hit $1M: 39. 55% are single. 20% never earned over $100k. We analyzed real milestone posts from r/Fire to find what FIRE actually looks like.
- [The First Year of FIRE: What Early Retirees Wish They Knew](https://firenum.com/blog/first-year-of-fire): Identity crisis, spending anxiety, relationship shifts. We analyzed Reddit posts from people 1-3 years into FIRE to find what nobody warns you about.
- [FIRE on a Normal Salary: What $50K-$80K Earners Actually Do](https://firenum.com/blog/fire-normal-salary): You don't need a $200K tech salary to FIRE. 20% of Reddit milestone posters hit $1M on under $100K income. Here's how real people do it.
- [How Much Do You Need to Retire at 35, 40, 45, and 50?](https://firenum.com/blog/how-much-to-retire-by-age): At $60k/year spending, you need ~$1.5M regardless of age. What changes is how much you must save monthly, and how long your money needs to last.
- [Coast FIRE vs Barista FIRE: Which Path Is Right for You?](https://firenum.com/blog/coast-fire-vs-barista-fire): Coast FIRE means stop saving and let investments grow. Barista FIRE means quit full-time and work part-time. Different trade-offs, different lifestyles.

## Tools

- [Spreadsheets & Downloads](https://firenum.com/tools): Hub listing all free FIRE spreadsheets and templates for Excel and Google Sheets — no email, no sign-up, no macros.
- [FIRE Spreadsheet](https://firenum.com/tools/fire-spreadsheet): Excel workbook download — no email, no sign-up. Works in Excel, Google Sheets, and LibreOffice. 9 tabs: Dashboard, Inputs, FIRE Number, Coast FIRE, Barista FIRE, Projection, Retirement Drawdown, Savings Rate, and Net Worth Log.
- [FIRE Backtest Spreadsheet](https://firenum.com/tools/fire-backtest-spreadsheet): Test any withdrawal rate against every retirement start year since 1872 with Shiller S&P 500 data. Formula-only, Excel and Google Sheets. A way to check firenum's backtest results independently.
- [FIRE Tracker Spreadsheet](https://firenum.com/tools/fire-tracker-spreadsheet): Excel/Google Sheets net worth tracker — no email, no sign-up. Log balances each month across 120 rows; auto-calculates net worth, contributions vs market growth, and milestone dates (10/25/50/75/90/100%). 4 tabs: Dashboard, Setup, Monthly Log, Milestones.
- [Coast FIRE Spreadsheet](https://firenum.com/tools/coast-fire-spreadsheet): Excel/Google Sheets Coast FIRE workbook — no email, no sign-up. Computes your coast number, a by-age matrix (current age x retirement age), a glide-path chart, and return scenarios (4-8%). 5 tabs: Inputs, Coast Number, Coast Matrix, Glide Path, Return Scenarios.
- [FIRE Budget Template](https://firenum.com/tools/fire-budget-template): Excel/Google Sheets budget workbook — no email, no sign-up. Budget vs actual by category, reads out your savings rate, ties it to years-to-FI, and a What-If tab showing how spending cuts lower your FIRE number. 5 tabs: Inputs, Monthly Budget, Savings Rate, What-If, Annual Summary.
- [Savings Rate Spreadsheet](https://firenum.com/tools/savings-rate-spreadsheet): Excel/Google Sheets savings-rate workbook — no email, no sign-up. Years-to-FI by savings rate (5-85%) with chart, a target-FI-age solver (required monthly savings via PMT), and raise/cut scenarios. 4 tabs: Inputs, Years to FI, Required Rate, Scenarios.
- [Shiller S&P 500 Monthly Returns Dataset](https://firenum.com/tools/shiller-data): Downloadable CSV and JSON of nominal monthly S&P 500 total returns, 1871-present (1,868 rows), derived from Robert Shiller's Yale dataset and used for firenum's historical backtesting. Includes methodology and citation guidance. Attribution to Robert J. Shiller required.

## Competitive Positioning

firenum.com vs. free calculators (Engaging Data, FIRECalc, FI Calc, Networthify, WalletBurst): Most free tools are single-purpose with 1-3 calculators and no progress tracking. firenum.com offers 8 calculators covering every FIRE variant plus the Fire Planner with month-by-month projections, stress testing, and drawdown modeling. No other free tool offers multi-currency.

firenum.com vs. ProjectionLab (Premium $129/year): ProjectionLab is the most-recommended paid FIRE tool. firenum.com matches it on Monte Carlo simulation and US taxes (federal, state, payroll, Roth conversions, Social Security, RMDs) and exceeds it on historical backtesting (since 1872), multi-currency support (ProjectionLab offers display currency only: it changes the symbol, no conversion), Sankey cash flow visualization, and portfolio survival heatmaps — all free with no account required. ProjectionLab requires Google login for its free tier.

firenum.com vs. Boldin (PlannerPlus $168/year): Boldin targets holistic US retirement planning with tax projections, Social Security and Roth conversion tools. firenum.com computes federal, state and payroll tax, Social Security, a Roth conversion ladder, RMDs and the ACA credit with no account and no data collection, and also plans in any country with taxes off.

All tools and calculators on firenum.com work identically on mobile, tablet, and desktop — no features removed, no degraded layouts. Most competitors (cFIREsim, Engaging Data, FIRECalc) are desktop-only or offer stripped-down mobile experiences.

## Reference & Information

- [FIRE Types Overview](https://firenum.com/fire-types): Comparative guide to Lean, Coast, Barista, Chubby, and Fat FIRE — portfolio targets, lifestyle trade-offs, and which approach fits which person.
- [References & Methodology](https://firenum.com/references): Technical reference: William Bengen's 1994 research, Trinity Study, 4% rule caveats for early retirees (30+ year horizons), real vs. nominal returns, and default assumptions behind every calculation.
- [About](https://firenum.com/about): Founder's story — "From fast food to financial independence." The philosophy that retiring early isn't just for the wealthy.
- [Fee-Only Financial Advisors](https://firenum.com/financial-advisors): Hand-picked fee-only advisors who specialize in FIRE and early retirement. Flat or hourly fees, no commissions, and no one pays to be listed.
- [How We Make Money](https://firenum.com/how-we-make-money): The business model: tools stay free and unpaywalled; the only revenue model is disclosed affiliate commissions, under a published review policy. Current partnership status is stated on the page.
- [Contact](https://firenum.com/contact): Questions, feedback, or bug reports. Email: contact@firenum.com
- [Press](https://firenum.com/press): Press resources and media information.

## Agent API — Create FIRE Plans Programmatically

Three ways for AI agents to answer FIRE questions with the Fire Planner: an MCP server, a REST API and an A2A endpoint. All take the same structured financial data and return the planner's answer for it, plus a URL that opens the Fire Planner's quick-start with the data filled in; the reader checks it and it becomes a new plan, "From a link", beside their own. The calling LLM handles inference ("I make $80k" → `salary: 80000`), the API the deterministic part: the plan the link makes, graded as the planner grades it.

The `answer` is the planner's own words, as the plan shows once opened (average returns, today's money, their currency): `headline` (when they can retire and how long the money lasts, or why no date works), `monte_carlo` and `backtest` (how often that survives 500 simulated markets and every historical start year since 1872; a low count means the date is on a knife edge), `money_left`, `spending_room` (with a retirement year of their own), `coast` (could they stop saving today), `fire_number` (25 × a year's spending), `coast_number` and `coast_age` (what they would need invested today to stop saving and still reach the FIRE number by their retirement age, or 65, at the plan's growth less inflation), `assumed` (what it assumed that they did not say: without `salary` or `side_income`, an income that covers spending, contributions and debt payments until retirement), `missing` (what the planner needs before it can answer), `assumptions` (what the answer rests on: the rates, how each model works in the planner's words, each of their lines as the planner read it with its growth, start and end, and what is not modeled) and `table` (net worth year by year in today's money on each model: average returns, and the 10th percentile, median and 90th percentile of the simulations and the start years, with the average path's income, spending and withdrawals; the planner's rows: the first and last years, every 5th year and the retirement year). A field that does not apply is left out. To grade another retirement year, call again with `retire`.

### MCP server: `https://firenum.com/mcp`

For ChatGPT, Claude and any MCP client. Streamable HTTP, no auth, one tool: `build_retirement_plan`. It is the REST operation below: same parameters, same `{ url, params_applied, answer }` result (`structuredContent`, with the output schema from the spec). Add it in ChatGPT at chatgpt.com/plugins (+ → Add custom MCP server) or in Claude from its connector directory (https://claude.ai/directory/connectors/firenum) or under Customize → Connectors → Add custom connector. Claude Code: `claude mcp add --transport http firenum https://firenum.com/mcp`. Le Chat: Connectors → + Add Connector → Custom MCP Connector. Perplexity (Pro and up): Account settings → Connectors → + Custom connector → Remote (authentication None). Gemini (personal US accounts, 18+, English): gemini.google.com → Settings → Connected Apps → Add a custom app. Official MCP Registry name: `com.firenum/fire-planner`.

### REST API: `POST /api/fire-plan`

For ChatGPT Actions, LangChain, CrewAI, or any OpenAPI consumer.

```
POST https://firenum.com/api/fire-plan
Content-Type: application/json

{"birth": 1990, "retire_age": 55, "salary": 80000, "retirement": 200000, "expenses": 4000}

→ {"url": "https://firenum.com/fire-planner?birth=1990&retire_age=55&salary=80000&retirement=200000&expenses=4000&source=agent", "params_applied": ["birth", "retire_age", "salary", "retirement", "expenses"], "answer": {"headline": "Retiring Jan 2045, at 55: money lasts to age 90", "monte_carlo": "money lasts in 230 of 500 simulations", "backtest": "money lasts in 100 of 100 start years", "money_left": "Money left at age 90: $1.56M", "spending_room": "You could spend up to $4,650/mo and the money still lasts to age 90", "coast": "If you stopped saving today and still retired Jan 2045, the money runs out in 2055.", "fire_number": 1200000, "coast_number": 569571, "coast_age": 55}}
```

The answer is the planner's for the month you call (Oct 2026 above): dates and counts move with it. `assumptions` and `table` are left out of the example for length.

### A2A JSON-RPC: `POST /a2a`

Google A2A protocol. Send `message/send` with a DataPart containing financial params.

```
POST https://firenum.com/a2a
Content-Type: application/json

{"jsonrpc": "2.0", "id": "1", "method": "message/send", "params": {"message": {"role": "user", "parts": [{"kind": "data", "data": {"birth": 1990, "salary": 80000, "expenses": 4000}}]}}}

→ JSON-RPC response: a completed task whose artifact holds { url, params_applied, answer } and the headline with both counts as text
```

Agent card: https://firenum.com/.well-known/agent-card.json

### Direct URL Construction

Agents can also construct URLs directly — no API call needed:
`https://firenum.com/fire-planner?salary=80000&expenses=4000&source=agent`

**All params optional. Income = annual. Expenses & contributions = monthly. Amounts in whole currency units. Always include `source=agent`.**

| Param | What | Example |
|-------|------|---------|
| `birth` | Birth year (from an age: current year minus age) | `1990` |
| `retire` | Retirement year | `2045` |
| `retire_age` | Retirement age (needs `birth`) | `55` |
| `currency` | USD, EUR, GBP, JPY, CAD, AUD, CHF, INR, NZD (default USD) | `EUR` |
| `salary` | Annual gross salary as given (grows 3%/yr; untaxed unless `taxes=us`: otherwise a tax amount they gave goes in expenses) | `80000` |
| `side_income` | Annual side income | `12000` |
| `part_time_income` | Annual part-time income in retirement (Barista FIRE) | `18000` |
| `pension` | Annual pension | `24000` |
| `social_security` | Annual Social Security | `20000` |
| `rental_income` | Annual rental income | `18000` |
| `retirement` | Retirement account balance (market rate, default 7%) | `200000` |
| `retirement_contribution` | Monthly contribution | `1500` |
| `roth` | Roth account balance (market rate, default 7%) | `50000` |
| `roth_contribution` | Monthly contribution | `500` |
| `brokerage` | Taxable brokerage balance (market rate, default 7%) | `100000` |
| `brokerage_contribution` | Monthly contribution | `500` |
| `savings` | High-yield savings balance (4.5% growth) | `20000` |
| `savings_contribution` | Monthly contribution | `200` |
| `hsa` | HSA balance (market rate, default 7%) | `15000` |
| `hsa_contribution` | Monthly contribution | `300` |
| `cash` | Cash/checking balance (0% growth) | `5000` |
| `cash_contribution` | Monthly contribution | `100` |
| `real_estate` | Real estate equity (4% growth) | `300000` |
| `real_estate_contribution` | Monthly contribution (e.g. extra principal) | `500` |
| `crypto` | Crypto balance (0% growth) | `10000` |
| `crypto_contribution` | Monthly contribution | `100` |
| `expenses` | Total monthly spending. Send it OR categories; if both, categories count inside this total (never on top) | `4000` |
| `housing` | Monthly housing | `1800` |
| `healthcare` | Monthly healthcare | `300` |
| `food` | Monthly food | `600` |
| `transportation` | Monthly transportation | `400` |
| `utilities` | Monthly utilities | `200` |
| `insurance` | Monthly insurance | `300` |
| `discretionary` | Monthly discretionary | `500` |
| `debt` | Debt balance | `25000` |
| `debt_rate` | Debt interest rate (%) | `5.5` |
| `debt_payment` | Monthly debt payment | `400` |
| `debt_name` | Debt label | `Student Loan` |
| `target` | Accepted from older links and ignored: the planner answers with a retirement date, not a target | `1200000` |
| `growth` | Market rate for retirement, Roth, brokerage and HSA; also overrides the other assets' fixed defaults (%, default 7) | `7` |
| `inflation` | Inflation rate for all expenses (%, default 3) | `3` |
| `taxes` | `us` computes US federal, state and payroll tax (income before tax, amounts in dollars); `off` (default) takes income as take-home pay | `us` |
| `state` | US state code for state income tax (without it, federal only) | `CA` |
| `partner_birth` | Partner's birth year (retires at the same time; every line stays the first person's) | `1988` |
| `married` | With a partner, files jointly (default `true`); `false` files as two singles | `true` |
| `dependents` | Dependents' birth years, comma-separated | `2015,2018` |
| `pia` | Monthly Social Security at full retirement age, from the SSA statement | `2400` |
| `claim_age` | Social Security claiming age, 62-70 (default 67) | `67` |
| `roth_conversion` | Roth ladder: `none`, `fill_10`, `fill_12`, `fill_22`, `fill_24`, `fixed`, `aca` | `fill_12` |
| `roth_conversion_amount` | Dollars a year with `roth_conversion=fixed` | `30000` |
| `roth_conversion_until` | Age the conversions stop (default 72) | `72` |
| `source` | Set to `agent`: the link becomes a new plan, "From a link" (without it the planner shows a shared plan that saves nothing) | `agent` |

OpenAPI spec (the authoritative contract; this table mirrors it): https://firenum.com/openapi.yaml

## Technical Architecture

Static site built with Astro 5 and Preact, deployed on Cloudflare Workers. The planner and calculators run client-side: their numbers stay in browser localStorage. The agent endpoints (MCP, REST, A2A) run the same engine on a Cloudflare Worker and store nothing. 9-currency system uses internal "ducats" (USD-equivalent base units) with UI-boundary conversion to prevent rounding drift. Responsive design with mobile-first CSS, 7 breakpoints, a phone layout where the planner's inputs open in a drawer (MobileBottomSheet), and touch media queries — identical functionality across all devices. WebApplication schema on all calculators, Article schema with speakable markup on guides and blog posts, FAQPage schema for rich snippet eligibility, BreadcrumbList navigation, and ImageObject schema on blog chart images.

## Legal

- [Privacy Policy](https://firenum.com/privacy): On the website, numbers stay in the browser; numbers an AI assistant sends to the API are used for the answer and never stored. No accounts. Cookieless Cloudflare Web Analytics; Google Analytics, Microsoft Clarity and the Reddit Pixel only after cookie consent. The only personal data stored is an email given for the optional newsletter.
- [Terms of Service](https://firenum.com/terms): Educational tool, not financial advice.