Build Your FIRE Plan With ChatGPT, Claude or Gemini

Tell your assistant your numbers. Get a link that opens your plan in the Fire Planner.

firenum team  · October 2026 · ~6 min read

TL;DR

  • Ask your assistant to read firenum.com/llms.txt. Then ask it for a Fire Planner link with your numbers.
  • Or connect firenum to ChatGPT, Claude or Gemini once, at https://firenum.com/mcp. Then just ask your question, and the answer comes from the Fire Planner itself.
  • Open the link. Your plan opens with its answer. Check the numbers in its inputs. If the link left out your age, spending or income, the planner asks for it first.
  • The plan is saved in your browser as a new plan, "From a link". No account needed; a free account keeps it on any device.
  • Assistants can read every firenum page as plain text. They can quote our calculators and research back to you.

Plenty of people already ask an AI assistant about retirement. The answers sound sure of themselves. The math behind them stays hidden. firenum gives your assistant the part it does well: turning what you tell it into a planner's inputs. The Fire Planner then does the math, month by month. It grades the answer three ways, so you can see how sure it is.

Build your plan from a chat

  1. Give the assistant this instruction with your own numbers. 
    Read https://firenum.com/llms.txt. Then write me a firenum Fire Planner link with source=agent. I was born in 1992 and want to retire at 50. My salary is $85,000 a year. I spend $3,200 a month. I have $120,000 in my 401(k).
  2. The assistant answers with a link. For the numbers above it looks like this: 
    https://firenum.com/fire-planner?birth=1992&retire_age=50&salary=85000&expenses=3200&retirement=120000&source=agent
  3. Open it. Your plan opens with its answer. For this example it reads "Retiring Jan 2042, at 50". Three cards grade it: Average returns, Monte Carlo and the historical backtest. A link without your age, spending or income opens "Finish your plan from a link" first, with what the link knew filled in, and asks for the rest.
  4. Check the inputs. Fix anything that looks wrong in the inputs beside the answer. The answer follows.
Line chart of net worth by age, 34 to 90, in today's dollars, for the example plan an assistant sends to the Fire Planner: born 1992, $85,000 salary, $3,200 a month spending, $120,000 in a 401(k), retiring at 50 in Jan 2042. Average returns: $1.2M at 50, $1.47M at 68, $2.21M at 90 (money lasts to 90). Monte Carlo median: $1.06M, $801k, $228k, with the worst 10% at $0 from 68; the money lasts in 281 of 500 simulations. Backtest median: $1.33M, $3.48M, $11.2M; it lasts in 98 of 98 start years.
One chat message, three grades: the money lasts to 90 on average returns, in 281 of 500 simulations and in 98 of 98 start years. Monte Carlo draws around the plan's 7% a year; the S&P 500 returned 9.4% since 1871, so history grades kinder. Free to use under CC BY 4.0: credit firenum.com with a link.

The planner saves it as a new plan called "From a link". It sits beside any plan you already have. Those plans stay as they are. From there it works like any plan you start yourself. You can add accounts, split your spending into categories and run the stress tests.

Connect firenum to your assistant

Connect firenum once and skip the instruction above. Ask your question with your numbers in it, such as "When can I retire? I'm 40, I have $600k invested and I spend $5k a month." The assistant sends those numbers to firenum. The Fire Planner works out its answer: when you can retire, how often your money lasts in 500 simulated markets and in every start year since 1872, whether you could stop saving today, and your FIRE number. The assistant tells you, with the link to your plan. Anything you left out is named in the answer: an income it had to assume, or an age it needs.

Part of your planWhat to tell the assistant
YouBirth year, and the year or age you want to retire
IncomeSalary, side income, pension, Social Security, rental income, part-time income after you retire. All per year.
Accounts401(k) or other retirement account, Roth, brokerage, HSA, high-yield savings, cash, home equity, crypto. Each can have a monthly contribution.
SpendingA monthly total, or categories: housing, healthcare, food, transportation, utilities, insurance, discretionary
DebtOne debt: balance, interest rate, monthly payment
US taxes"US taxes on", your state, a partner's birth year, children's birth years, your Social Security statement's benefit and claiming age, a Roth conversion ladder
AssumptionsMarket growth, inflation and currency (9 currencies)

Income is per year. Spending and contributions are per month. Mixing those up is the most common slip, so say which one you mean.

A link holds the starting point of a plan. Life events, check-ins and further debts go in by hand afterwards, in the planner's inputs.

Check what the assistant wrote

The assistant only writes the link. The planner does every calculation, exactly as it does when you type the numbers yourself. The weak spot is the copying.

Bar chart of the earliest retirement age the Fire Planner finds for a 34-year-old earning $85,000 a year, spending $3,200 a month, with $120,000 in a 401(k), and for each per-month/per-year slip: as typed, age 45 (Jul 2037); yearly salary sent as monthly ($1,020,000 a year), age 35 (Aug 2027); monthly salary sent as yearly ($7,083 a year), never, savings run out in 2031; monthly spending sent as yearly ($38,400 a month), never, savings run out in 2027; yearly spending sent as monthly ($267 a month), age 34, retire now.
One unit slip moves the same plan from retiring at 45 to retiring now, or to never. Check Income and Spending against your payslip and bank statement before you trust the date. Free to use under CC BY 4.0: credit firenum.com with a link.

Ask about our research and calculators

Every firenum page also comes as plain Markdown for AI tools. Add .md to an address, such as firenum.com/coast-fire.md. An assistant that asks for Markdown gets it at the normal address too. llms.txt is the map. It lists the calculators, the guides and the research posts. It also says what the planner calculates and what it leaves out.

Questions to try:

Our robots.txt lets AI crawlers in. Search assistants can find firenum pages. They can link to them in their answers.

What stays private

For developers and agent builders

Everything above runs on public endpoints with no key and no account.

The developer page has the full parameter list and examples.

Frequently Asked Questions

Try it with the assistant you already use.

Open Fire Planner → Developer docs →

Related reading