FIRE Number
Financial Independence number from annual spending and a safe withdrawal rate (rule-of-thumb).
About this calculator
This calculator inverts the safe withdrawal rate to answer the core FIRE (Financial Independence, Retire Early) question: how big does my portfolio need to be? The math is a single division: FIRE number = annual spending ÷ withdrawal rate. At the classic 4% rule, that means multiplying annual spending by 25 (since dividing by 0.04 is the same as multiplying by 25) — the rule of thumb popularized by the Trinity Study, which found a 4% initial withdrawal, adjusted for inflation each year, historically survived a 30-year retirement across most market conditions for a portfolio split between stocks and bonds. The calculator also reports your target's monthly spend (simply annual spending divided by 12) and an "annual from rule check" figure, which just multiplies your computed FIRE number back by the withdrawal rate — a sanity check that should equal your original annual spending input.
The withdrawal rate is clamped between 1% and 10% here, but in practice most FIRE planning clusters around 3-4%: a lower rate (3-3.5%) is often used for early retirees with 40+ year horizons, since the original 4% research assumed a standard 30-year retirement. Key limitations to keep in mind: this is a static rule-of-thumb, not a Monte Carlo simulation — it ignores sequence-of-returns risk, doesn't account for Social Security, pensions, or part-time income that could reduce the number needed, and assumes your spending stays flat in real terms throughout retirement. Treat the result as a ballpark planning target, not a guarantee.
Financial Disclaimer
This calculator is for educational purposes only and does not constitute financial advice. Results are estimates based on the inputs provided. Consult a qualified financial advisor before making investment or financial planning decisions.
Inputs
Results
FIRE portfolio
$1,500,000.00
≈ 4 average U.S. homes
How to Use This Calculator
- Enter Annual spending and Safe withdrawal %.
- Review the FIRE portfolio ($) result.
- Use Monthly spend ($) and Annual from 4% rule check ($) to inform your decision.
How the result changes with Safe withdrawal %
| Safe withdrawal % | FIRE portfolio |
|---|---|
| 2% | $3,000,000.00 |
| 3% | $2,000,000.00 |
| 6% | $1,000,000.00 |
| 10% | $600,000.00 |
What each input means
- Annual spending
- Expected annual expenses in retirement.
- Safe withdrawal %
- Planned withdrawal rate (often 3–4%).
How this is calculated
Worked example, using the default values
- Identify Input ParametersAnnual spending = 60000, Safe withdrawal % = 4 = 2 input(s) provided
- Calculate FIRE portfolioFIRE portfolio = annual / swr1500000 = $1,500,000
- Calculate Monthly spendMonthly spend = annual / 125000 = $5,000
- Calculate Annual from 4% rule checkAnnual from 4% rule check = annual / swr60000 = $60,000
Engine last updated . Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does a 4% withdrawal rate mean multiplying annual spending by 25?
The calculator divides annual spending by the withdrawal rate expressed as a decimal, and dividing by 0.04 is mathematically identical to multiplying by 25. So $60,000 in annual spending at a 4% rate gives $60,000 / 0.04 = $1,500,000, the same number you'd get from $60,000 × 25.
What is the 'Annual from 4% rule check' output actually checking?
It multiplies your calculated FIRE number back by the same withdrawal rate you entered, which should return you to your original annual spending figure. It exists purely as an internal consistency check — if it ever doesn't match your annual spending input, something upstream is inconsistent.
Should I use a lower withdrawal rate than 4% if I'm retiring in my 30s or 40s?
Many early retirees use 3% to 3.5% instead of 4%, since the original Trinity Study research behind the 4% rule was tested against a standard 30-year retirement horizon. A 40+ year retirement gives market downturns more time to compound against a portfolio, so a lower, more conservative withdrawal rate is commonly used to reduce that added risk — you can test this directly by lowering the Safe Withdrawal % input.
What does this FIRE number calculation not account for?
It's a static rule-of-thumb, not a Monte Carlo simulation — it ignores sequence-of-returns risk (the danger of a market crash early in retirement), and it doesn't factor in Social Security, pensions, or part-time income that could lower the portfolio you actually need. It also assumes your real spending stays flat throughout retirement, which many people's actually don't.
Why is the Safe Withdrawal % input limited to a range of 1% to 10%?
The calculator clamps the input to that range to keep results within a plausible planning zone, but in practice most FIRE strategies cluster much narrower, around 3% to 4%. Rates far outside that band produce numbers that no longer reflect how the underlying research or common retirement planning practice actually works.
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