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FIRE Calculator

Your FIRE number is annual spending times 25 — see when your savings and contributions get you there.

Personal Finance · Reviewed by FreeCalculators Editorial · Updated 2026-08-21

Your details

What you expect to spend per year once work is optional.

7% is the long-run inflation-adjusted stock average.

The 4% rule; lower is more conservative.

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How it works

FIRE — financial independence, retire early — collapses the whole retirement question into one target number: the invested sum from which you can draw your annual spending for the rest of your life, and everything else on this page is just the route to it. That target, the FIRE number, is your expected annual spending divided by a safe withdrawal rate. At the classic 4% rule it is spending times 25, so a $48,000 retirement budget needs $1.2 million invested; at a more cautious 3.5% the multiple is 28.6, and at an aggressive 5% it is 20. The calculator then projects your current savings forward, adding your monthly contribution and compounding at your return rate, and finds the year your balance first equals the target — that date is the real answer, the number is just a milestone on the way. Two forces move the date and they are not equal. Contributing more grows the pile faster. But spending less works twice: it shrinks the FIRE number itself and simultaneously frees more cash to invest, which is why your savings rate predicts the date better than your income does. A household spending $48,000 needs $1.2 million and, saving $2,000 a month from a $120,000 start at a 7% real return, reaches it in about 17 years; the same household spending $40,000 needs only $1 million and the $8,000 a year it no longer spends also accelerates the journey. The output savings rate is simply your annual contribution divided by your annual spending — here $24,000 on $48,000, or 50% — and it is the best single predictor of how soon work becomes optional. The engine compounds monthly, twelve contributions a year, and searches for the crossing year rather than using a closed formula, which is why the answer can land on a fraction such as 17.2 years. Monthly passive income is your annual spending divided by 12, which at $48,000 is $4,000 and, under the 4% rule, is exactly 4% of the $1.2 million target, so the two numbers agree by construction. The still-to-accumulate figure is the gap the compounding has to build. Honest limits: the model assumes a constant real return, so it ignores sequence-of-returns risk — a bad market stretch early in retirement can matter far more than the average suggests, which is the main argument for a cash buffer or a more conservative withdrawal rate. It also assumes you keep contributing to the crossing date, realistic for lean-FI but not for someone who quits at a part-time job, and it treats all spending as equal when trimming a few large fixed costs moves the number far more than many small optimisations. On the withdrawal rate itself, 4% comes from the Trinity study of historical US market periods and has held for 30-year retirements, but it is a planning anchor, not a law; for a 40- or 50-year retirement, or lower expected returns, 3.5% or 3% is the more defensible choice at the cost of a larger target and a later date. Remember FIRE is a spectrum — lean-FI covers reduced must-pay expenses, coast-FI lets current savings grow to the target alone, barista-FI covers the gap with part-time work — and this tool reports the full-independence date, with the variants as different, smaller targets that often arrive years earlier.

Formula


                FIRE number = annual spending / withdrawal rate   (4% rule => x25, 3.5% => x28.6)
balance compounds monthly: 12 contributions/yr at return rate/12
years to FIRE = first year the balance >= FIRE number (binary-searched, may be fractional)
monthly passive income = annual spending / 12   (= withdrawal rate x FIRE number)
remaining = FIRE number - current savings
savings rate = (monthly contribution x 12) / annual spending x 100

Worked example — spend $48,000, save $120,000, $2,000/mo, 7% real, 4% withdrawal
  FIRE number   = 48,000 / 0.04            = $1,200,000
  years to FIRE = engine                    = 17.21  (about 17 years, 207 months)
  remaining      = 1,200,000 - 120,000      = $1,080,000
  monthly income = 48,000 / 12              = $4,000
  savings rate   = (2,000 x 12) / 48,000    = 50%

Shift the withdrawal rate
  3.5% => 48,000 / 0.035 = $1,371,429  (more conservative, later date)
  5.0% => 48,000 / 0.05  = $960,000    (aggressive, earlier date)

Spend less, twice: $40,000 at 4% => $1,000,000 target AND $8,000/yr freed to invest

Tips

  • Cutting spending helps twice — it shrinks the FIRE number and frees more to invest, so a $1 cut to spending beats a $1 raise.
  • The 4% rule is a historical backtest, not a guarantee; for a retirement longer than 30 years use 3.5% and accept the later date.
  • Use a real (inflation-adjusted) return such as 7% for stocks or 5-6% for a balanced portfolio, so the answer stays in today's purchasing power.
  • Watch sequence-of-returns risk: a bad market stretch early in retirement hurts more than the average implies, which argues for a cash buffer or a more conservative withdrawal rate.

Frequently asked questions

What is my FIRE number?
Your annual retirement spending divided by your safe withdrawal rate. At the classic 4% rule it is spending times 25 — $48,000 a year needs $1.2 million invested — and at a more conservative 3.5% it is times 28.6. That sum is what your portfolio must reach so you can draw your spending indefinitely.
How is years to FIRE calculated?
The calculator compounds your current savings and monthly contributions monthly at your return rate, year by year, and reports the first year your balance reaches the FIRE number. With the defaults that is about 17.2 years (207 months). Higher contributions or returns shorten it; a higher FIRE number lengthens it.
Is the 4% rule safe?
It comes from the Trinity study of historical US 30-year periods and has held up across them, but it is a planning anchor, not a promise. For retirements longer than 30 years, or if you expect lower future returns, many planners prefer 3.5% or 3%, which raises the target and pushes the date back in exchange for more safety.
Why does cutting spending beat earning more?
Because it works on both sides at once. Spending $8,000 less a year shrinks your FIRE number by $200,000 at the 4% rule and simultaneously frees $8,000 a year to invest. A raise only adds to contributions, and only if your lifestyle does not absorb it first.
What return rate should I use?
About 7% for a diversified stock portfolio after inflation, which keeps the answer in today's purchasing power, or roughly 10% nominal. For a balanced portfolio with bonds, 5-6% is the more prudent assumption. The result is a plan, so treat the rate as an estimate and test a lower one.
What does the savings rate mean here?
It is your annual contribution divided by your annual spending — $24,000 on $48,000, or 50%, at the defaults. It is the single best predictor of the date, because a higher rate both grows the pile faster and signals a lower target.