FIRE number calculator

Your FIRE number is annual spending divided by a safe withdrawal rate. The rate you pick moves the target by hundreds of thousands of dollars — so this calculator shows it at 3.0%, 3.5%, and 4.0%, not just one.

How the math works

The FIRE number is the portfolio big enough that a fixed slice of it, withdrawn every year, covers your spending. That slice is the safe withdrawal rate. The number is its inverse applied to annual expenses.

A 4.0% withdrawal rate means you need 1 ÷ 0.04 = 25 times your spending. That "25×" is the rule of 25, and it's the same statement as the 4% rule read backwards. Drop the rate and the multiplier climbs: 3.5% needs 28.6×, 3.0% needs 33.3×.

To estimate when you hit the number, the calculator grows your current balance and your annual contributions at the return you enter, then solves for the year the total crosses the target:

Enter the return as a real return — after inflation — and the resulting FIRE number stays in today's dollars. The long-run real return on a broad stock index has averaged 7.0%, which is the default here. Nominal returns run higher, but so does the target they'd have to fund.

Worked example

Take a household that expects to spend $48,000 a year in retirement. At the classic 4.0% rate, the FIRE number is $1,200,000 — the same portfolio a 67-year-old drawing 4% would hold to fund $48,000 in year one, then adjust for inflation after that.

The rate is not fixed by nature, though. It's a bet on how long the money has to last. Here is the same $48,000 of spending at three rates:

• 4.0% → 25× → $1,200,000. The Trinity-era number, tested on 30-year retirements.
• 3.5% → 28.6× → $1,371,429. A common adjustment for a longer horizon.
• 3.0% → 33.3× → $1,600,000. For a 40-to-50-year retirement.

Same spending, a $400,000 spread in the target. Moving from 4.0% to 3.0% doesn't add a rounding error — it adds a third to the number. A calculator that quotes only the 25× figure is answering a question about a 30-year retirement, which is not the question an early retiree is asking.

When this calculator is wrong

The 4% rule is a starting point, not a guarantee. The Trinity Study found 4% withdrawals held up across most historical 30-year periods for stock-heavy portfolios — not all of them, and not across the 40-, 50-, and 60-year horizons most FIRE plans stretch it to. Retiring at the 4% rate is a reasonable plan with sequence-of-returns risk that needs watching, not a set-and-forget answer. The exception: someone with substantial Social Security and a paid-off home is drawing 4% on a smaller remaining portfolio, and the floor makes the number more conservative than it looks.

Other ways the headline number misleads:

• It's pre-tax. A $48,000 withdrawal from a traditional 401(k) or IRA is taxable income; what lands in your account is less. If your money is mostly in traditional accounts, the true FIRE number is higher than the calculator shows — you have to fund the tax as well as the spending. Money in a Roth or a taxable account with a low cost basis changes this.
• It plans to a single age. Longevity is a tail, not a point. Roughly 25% of 65-year-old women are still alive at 90 and about 10% at 95, per the SSA life table. A number sized to an "average" lifespan leaves a real chance of outliving it.
• It assumes flat spending. Real retirement spending isn't a straight line — it tends to fall in the middle years and rise again for healthcare late. And before Medicare at 65, an early retiree buys their own health insurance, which the $48,000 has to absorb.
• It ignores inflation drift in the rate. The whole model assumes you withdraw the same real amount every year. A stretch of high inflation forces either a higher nominal withdrawal or a real spending cut. The calculator can't see which one you'll choose.

What to do with the result

Pick the withdrawal rate that matches your horizon before you fixate on the number. If you're retiring at 60 or later, 4.0% and the 25× number are defensible. If you're aiming to stop work in your 40s, model 3.0–3.5% and treat the higher target as the real one — the extra $400,000 in the example is the price of the longer runway, not padding.

Then check the gap between where you are and the number. If the calculator says you're a decade or more out, the lever that moves the date most is the savings rate, not the return assumption — the years-to-reach figure is far more sensitive to what you add each year than to whether the market returns 6% or 8%. If it says you're close, the work shifts from accumulating to sequencing: which accounts you draw from first, and how you'll cut spending in a down year without touching principal at the bottom.

Common questions

What is a FIRE number?

It's the portfolio large enough to cover your annual spending indefinitely at a chosen safe withdrawal rate. At a 4% rate it's 25 times your yearly expenses; at 3% it's 33.3 times. The number is in today's dollars if you use a real (after-inflation) return to project toward it.

Is the FIRE number 25 times expenses or something else?

25× is the number at a 4% withdrawal rate, because 25 is 1 ÷ 0.04. It's not a universal constant. Use a lower rate for a longer retirement and the multiplier rises — 28.6× at 3.5%, 33.3× at 3.0%. The multiplier is a choice about horizon and risk, not a fixed figure.

Does the 4% rule work for early retirement?

It was tested on 30-year retirements, not the 40-to-60-year spans early retirees plan for. Over a longer horizon the same 4% withdrawal has more years to hit a bad sequence of returns. Many early retirees use 3.0–3.5% instead, which raises the FIRE number but lowers the odds of running out.

Should my FIRE number account for taxes?

Yes, if your savings are in traditional 401(k) or IRA accounts, because withdrawals from those are taxed as ordinary income. The calculator's number covers spending, not the tax on top of it, so the real target is higher. Roth and taxable-account balances change the math because their withdrawals are taxed differently or not at all.

How is Coast FIRE different from a regular FIRE number?

Coast FIRE is the smaller amount that, left to compound without any further contributions, grows into your full FIRE number by traditional retirement age. It answers a different question — "can I stop saving?" rather than "can I stop working?" This calculator sizes the full number and the years to reach it with contributions included.