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FIRE calculator

FIRE means financial independence, retire early. Enter your take-home pay and spending to see your FIRE number, your savings rate and how many years until your investments can cover your life.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Already have a good start? See if you can stop saving with the Coast FIRE calculator, then stress-test the withdrawals with the Monte Carlo withdrawal calculator.

How it's calculated

FIRE number F = yearly spending ÷ withdrawal rate    (at 4%, F = 25 × spending)

Your yearly savings S are income minus spending. Starting from what you've invested, P, and adding S at the end of each year at a real return r, the years until you reach F are:

n = ln((F × r + S) ÷ (P × r + S)) ÷ ln(1 + r)    (with r = 0: n = (F − P) ÷ S)

Everything is in today's dollars, which is why the return is "real": the return after inflation. If you expect 7% before inflation and 2% inflation, use about 5%.

Worked example

You take home $100,000 and spend $60,000, a 40% savings rate. Your FIRE number is 60,000 ÷ 0.04 = $1,500,000. With $100,000 invested and a 5% real return: n = ln((1,500,000 × 0.05 + 40,000) ÷ (100,000 × 0.05 + 40,000)) ÷ ln(1.05) = ln(115,000 ÷ 45,000) ÷ 0.04879 = 19.2 years.

Why the savings rate matters most

Spending less does two things at once: you save more each year, and you need a smaller FIRE number. That's why the table under the result moves so fast. Income only matters through the gap between what you earn and what you spend.

Lean, regular and fat FIRE

These are loose labels, not official cutoffs. Lean FIRE means a frugal budget, Fat FIRE a comfortable or generous one. The preset buttons use round numbers to show the difference; replace them with your own spending.

Where the 4% rule comes from

In 1994 financial planner William Bengen tested US stock and bond returns going back to 1926. He asked how much a retiree could take in the first year, then raise each year for inflation, without running out over 30 years in any period he tested. With half to three-quarters in stocks, the answer was about 4%. In 1998 three Trinity University professors (Cooley, Hubbard and Walz) ran a similar test, often called the Trinity study, and reported success rates for different withdrawal rates, time spans and stock/bond mixes.

Dividing spending by 4% is the same as multiplying it by 25. A 3.5% rate means about 28.6×, and 3% means about 33×.

Limits of the 4% rule for early retirees

  • It's based on past US returns, one of the strongest markets in history. Future returns may be lower.
  • It was tested over 30 years. Retiring at 45 might need the money to last 50 years, which points to a lower rate.
  • It ignores fees and taxes. A 1% yearly fee takes a large bite out of a 4% withdrawal.
  • It assumes you never cut spending. In practice people who trim spending after a bad year can usually start higher.

Limitations

  • Health insurance before Medicare at 65, which can be a large cost for early retirees.
  • Social Security, which could lower what you need later on. A lower spending figure can stand in for it.
  • Taxes on withdrawals and penalties for taking money from retirement accounts before 59½.

A planning estimate, not financial, tax or investment advice. Every assumption is listed under the result.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

  • $60,000 spending at 4% is a $1,500,000 FIRE number ✓
  • Saving $40,000 a year from $100,000 at 5% real: 19.2 years ✓
  • 0% real return from $0: 1,500,000 ÷ 40,000 = 37.5 years ✓
  • Already invested $2,000,000: you're there ✓
  • Spending more than income: not reachable ✓
  • No income: savings rate shows a dash, not 0% ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

What is my FIRE number?

Your yearly spending divided by your withdrawal rate. At 4% it's 25 times spending: $40,000 a year needs $1,000,000, $60,000 needs $1,500,000.

How many years until I can retire early?

It depends mostly on your savings rate. With nothing invested and a 5% real return, saving 50% of take-home pay takes about 17 years, and saving 25% takes about 32 years.

What is Lean FIRE and Fat FIRE?

Lean FIRE is financial independence on a tight budget; Fat FIRE is on a generous one. There are no official dollar cutoffs, so use the spending you actually expect.

Should I use a 4% withdrawal rate for early retirement?

4% was tested over 30-year retirements. If you retire in your 30s or 40s, the money may need to last 50 years or more. A lower rate such as 3% to 3.5% gives a bigger cushion and raises the FIRE number to about 29 to 33 times spending.

What return should I use?

Use a real return, after inflation and fees. Long-run stock-heavy portfolios are often modeled at 4% to 6% real; try a lower figure to be cautious.

Related calculators

Coast FIRE calculatorHow much you need invested today to stop saving and still retire on time, plus Barista FIRE.How much do I need to retire?Your target nest egg from spending, other income and a withdrawal rate, and whether you're on track.Retirement withdrawal calculatorMonte Carlo odds your savings last, with 10th, 50th and 90th percentile balances.Investment calculatorEnd balance with monthly or yearly contributions that rise each year, or the contribution you need.