How the FIRE Calculator Works
Two steps. First the target: your monthly spending × 12, divided by your withdrawal rate. At the 4% rule that is 25× a year of spending, so $4,000/month needs $1,200,000. That is your FIRE number.
Then the date: what you have invested today plus what you save each month, compounded monthly at your expected return, until the portfolio reaches the target. With the defaults (age 30, $50,000 invested, $2,000/month saved, 5% after inflation) that takes 24 years: FIRE at 54.
Along the way it checks one more thing: whether you are already Coast FI. If what you have today grows to your FIRE number by 65 without another dollar saved, it says so. Anything after that is optional saving that buys you an earlier date.
Every number is in today's money. The return is after inflation, so $1,200,000 in 24 years buys what $1,200,000 buys now.
Years to FIRE by Savings Rate
Your savings rate does double duty: it is what you invest each month, and the rest is what you spend, which sets the target. That is why it decides the date more than anything else. Starting from nothing invested, at a 5% real return and a 4% withdrawal rate, with the same math as the calculator (whole years, rounded up):
| Savings rate | Years to FIRE | FIRE age if you start at 30 |
|---|---|---|
| 10% | 51 | 81 |
| 20% | 36 | 66 |
| 30% | 28 | 58 |
| 40% | 22 | 52 |
| 50% | 17 | 47 |
| 60% | 13 | 43 |
| 70% | 9 | 39 |
Savings rate is the share of take-home pay you invest; income cancels out, so the table holds at any salary. Money already invested shortens every row. Going from 10% to 30% cuts 23 years; going from 30% to 50% cuts another 11.
Which Calculator Do You Need?
| Your question | Calculator |
|---|---|
| How much do I need, and when do I get there? | This page |
| I have a target in mind. When do I reach it? | When Can I Retire? |
| Just the number, from my spending | FIRE number calculator |
| Can I stop saving and let it grow? | Coast FIRE calculator |
| What if I keep working part-time? | Barista FIRE calculator |
| Retiring on a tight budget | Lean FIRE calculator |
| Retiring on $100,000+ a year | Fat FIRE calculator |
| How long will my money last? | Retirement withdrawal calculator |
| How often does my plan survive 500 random markets? | Monte Carlo retirement calculator |
| Should I claim Social Security at 62, 67 or 70? | Social Security break-even calculator |
| How do I get to my 401(k) before 59½? | Roth conversion ladder calculator |
| Will my plan survive a crash? | Fire Planner (Monte Carlo + backtesting) |
What This Calculator Doesn't Do
It assumes the same return every year. Markets don't deliver that. A crash in your first years of retirement can sink a plan that works on average: that is sequence-of-returns risk, and an average return can't show it. It also leaves out taxes, raises, a mortgage that ends and pensions that start.
The Fire Planner takes the same numbers and the rest of your life: income, expenses, assets, debts and one-time events, month by month. It then grades your retirement date three ways: average returns, 500 Monte Carlo simulations and every start year since 1872. The result button above opens it with your numbers already filled in. Free, no sign-up, and everything stays in your browser.
Comparing tools? See how firenum stacks up against FIRECalc, cFIREsim and ProjectionLab in our FIRE calculator comparison.
Frequently Asked Questions
A FIRE (Financial Independence, Retire Early) calculator answers two questions: how much you need for work to be optional, and when you get there. This one sets the target at your annual spending divided by your withdrawal rate (25× spending at 4%), then compounds what you have invested plus what you save each month until the portfolio reaches it. If you only need the target, use the FIRE number calculator.
Mostly a function of your savings rate. Starting from zero at a 5% real return and the 4% rule: a 10% savings rate takes 51 years, 30% takes 28, 50% takes 17, and 70% takes 9. Money you already have invested shortens every one of those. Enter your own numbers above for your age.
A real (after-inflation) return. The default is 5%. U.S. stocks have returned about 7% a year after inflation over the long run (Damodaran's NYU dataset 6.9%, 1928-2024; Shiller's Yale dataset 7.1%, 1871-2024). Planning at 5% leaves room for bonds, fees and a weaker decade. Don't enter a nominal return like 10%: the FIRE number here is in today's money.
4% is the classic number from the Trinity Study: 25× your annual spending lasted 30 years in most historical periods. An early retirement can last 40-50 years, so many plan at 3.5% (about 29× spending). Each half point lower raises the FIRE number and pushes the date out. The 4% rule guide covers the research.
You are Coast FI when what you have invested today grows to your FIRE number by 65 with no new savings at all. The calculator checks that for you and says so under the result. For the number itself by age, use the Coast FIRE calculator.
This calculator starts from your spending and works out the target for you. When Can I Retire? starts from a target you already have in mind, a portfolio value or a monthly income, and tells you when you reach it.
Yes. This calculator supports 9 currencies: USD ($), EUR (€), GBP (£), JPY (¥), CAD, AUD, CHF, INR (₹), and NZD. Use the currency selector in the navigation bar to switch. The math is the same in every currency. Your choice is saved in your browser.