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FIRE & Retirement calculator

FIRE Number Calculator

Calculate your financial independence number from annual spending and a safe withdrawal rate, plus your years to FI.

Your target yearly expenses
4% rule = 25x spend
After inflation

A FIRE calculator computes your FIRE number — the portfolio size that can fund your annual spending indefinitely — and estimates how many years of saving it takes to reach it. The number comes from the safe withdrawal rate framing popularized by William Bengen's research and the Trinity study: historically, a retiree who withdrew 4% of their starting portfolio in year one and adjusted that amount for inflation each year after had a high probability of not exhausting a stock-and-bond portfolio over a 30-year retirement. Stated the other way around, funding your lifestyle takes roughly 25 times your annual spending, since 1 ÷ 0.04 = 25.

Enter your target spending, withdrawal rate, current savings, annual contributions, and expected real return above. The tool reports your FIRE number, your estimated years to reach it, the calendar year that implies, and the annual withdrawal your target supports.

How it's calculated

The target is a single division:

FIRE number = annual spending ÷ (withdrawal rate ÷ 100)

The years-to-target figure inverts the future-value-with-contributions annuity formula:

n = ln((target · r + PMT) / (PV · r + PMT)) / ln(1 + r)

where PV is current savings, PMT the annual contribution, and r the real annual return. In plain terms: your portfolio grows from two engines, compounding on what is already invested and new contributions, and the formula solves for the year the combined curve crosses your target. Full formulas and the underlying Bengen/Trinity citations are on our methodology page.

Worked example: $48,000 spending, $24,000 saved per year

Take the calculator's default scenario: $48,000 of annual spending at a 4% withdrawal rate gives a FIRE number of $1,200,000 — which then supports $48,000 a year of withdrawals, closing the loop. Starting from $90,000 invested with a 5% real return, here is how the timeline responds to the annual contribution, computed with the same engine as the tool above:

Annual contribution Years to $1,200,000 Reached at (from 2026)
$12,00030.2 yr~2057
$24,00022.2 yr~2049
$36,00017.7 yr~2044
$48,00014.8 yr~2041

Doubling the contribution from $12,000 to $24,000 cuts eight years off the timeline; doubling again cuts another seven and a half. The savings rate is the dominant lever, and it works from both ends — saving more also usually means spending less, which shrinks the target itself. The withdrawal rate matters nearly as much: at the same $48,000 spending, a conservative 3.5% rate raises the target to $1,371,429 and a 3% rate to $1,600,000, while a 5% rate lowers it to $960,000. Small-sounding assumption changes move the goal by hundreds of thousands of dollars, which is why the honest approach is to bracket your inputs rather than trust one run.

When should you use this calculator?

Use it to turn a vague ambition into a dated, sized target: your number, your years, and the calendar year they imply. It is built for sensitivity testing — re-run it at 3.5% and 4% withdrawal rates, at 4% and 6% real returns, and with contribution levels you could actually sustain, and read the spread as your realistic range. It is also the right tool for measuring trade-offs in concrete units: a $500 monthly spending cut is $6,000 more contributed and $150,000 off the target at a 4% rate, and the tool shows exactly how many years that combination buys. Once you are curious whether your existing balance could already carry you to a traditional retirement with no further saving, that is a different question — the Coast FIRE calculator answers it.

The tool answers the arithmetic. Whether early retirement is feasible or wise for you — healthcare before 65, sequence-of-returns risk in the first decade, the psychology of leaving work — sits outside it. Treat the projected year as a planning marker to revisit annually, not a promise.

Assumptions and limitations

  • Returns are a constant real rate compounded annually. Actual returns are volatile, and a weak early-retirement sequence can exhaust a portfolio the average says should survive.
  • The 4% rule is a heuristic from historical U.S. data over 30-year horizons, not a guarantee. Retirements of 40–50 years, high fees, or heavy bond allocations argue for a lower rate.
  • Enter returns net of inflation and fees so results are in today's dollars. Using nominal returns silently overstates progress.
  • Contributions are assumed constant every year until the target; pauses, raises, and windfalls are not modeled — re-run with updated numbers instead.
  • Taxes are not modeled. Withdrawals from pre-tax accounts are taxable, so use a spending figure that includes the taxes you will owe.
  • Outside retirement income (Social Security, pensions) is not modeled; it reduces the spending your portfolio must cover and therefore your number.

This page is educational content about the FIRE-number calculation. It is not financial advice and does not consider your personal circumstances. For decisions that matter, consult a qualified professional.

Last reviewed: 2026-07-09

Frequently asked questions

What is the 4% rule?
The 4% rule is a retirement guideline drawn from the Trinity study (and William Bengen's earlier research): historically, a retiree who withdrew 4% of their starting portfolio in the first year, then adjusted that amount for inflation each year, had a high probability of not running out of money over a 30-year retirement. Stated the other way, it implies a nest egg of 25 times your annual spending. It is a planning heuristic, not a guarantee — it is based on historical U.S. data, assumes a stock/bond portfolio, and does not account for every fee, tax, or unusually long retirement. Some early retirees use a more conservative 3–3.5% rate.
How do I calculate my FIRE number?
Divide your expected annual retirement spending by your chosen safe withdrawal rate. At a 4% rate that is annual spending ÷ 0.04, or equivalently annual spending × 25. For example, $40,000 of yearly spending implies a $1,000,000 FIRE number; a more cautious 3.5% rate raises it to about $1,143,000. Use spending figures that include taxes. For projecting how long it takes to get there, enter returns as real (inflation-adjusted) percentages so the result is expressed in today's dollars. This calculator computes both your number and your estimated years to financial independence.
How much money do I need to retire early?
The standard framing: enough invested that a sustainable withdrawal covers your annual spending — at a 4% withdrawal rate, 25 times what you spend in a year. Spending $48,000 a year implies $1,200,000; because early retirements can run 40 years or more, many planners use a more conservative 3.5% (about $1,371,000 for the same spending) or 3% ($1,600,000). The number is driven by spending, not income: a high earner who spends little needs less than a moderate earner who spends more. Include taxes and healthcare in the spending estimate — both are commonly underestimated.
Does the FIRE number account for Social Security or a pension?
The basic calculation does not — it sizes a portfolio to cover all of your spending on its own. Outside income changes the arithmetic simply: subtract the guaranteed annual amount from your spending before multiplying by 25. If you spend $48,000 and expect $18,000 a year from a pension or Social Security, the portfolio only needs to cover $30,000, cutting the target from $1,200,000 to $750,000 at a 4% rate. Timing matters for early retirees, though — benefits that begin at 62 or later leave a gap the portfolio must bridge alone, so many plan the early years at the full number.
How long does it take to reach FIRE?
It depends overwhelmingly on how much you save relative to your target. As a computed example at a 5% real return: starting from $90,000 and contributing $24,000 a year, a $1,200,000 target is about 22 years away; doubling the contribution to $48,000 cuts it to under 15 years, while halving it to $12,000 stretches it past 30. The savings rate works twice — more saved accelerates the portfolio, and the lower spending that usually accompanies it shrinks the target. Market returns matter, but over long horizons the contribution rate is the lever you control. This calculator computes your own timeline.

Coast FIRE

Find out if your current savings will coast to a full retirement with no further contributions — and your exact Coast FIRE number.

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