FIRE Number Calculator
This FIRE number calculator shows how much you need saved to retire — full-time work optional — based on your expected annual expenses and a safe withdrawal rate. Enter your numbers to see your target portfolio size, and how it shifts at a more or less conservative withdrawal assumption.
What you expect to spend per year once retired — not your current income.
The percentage of your portfolio you plan to withdraw each year — 4% is the traditional benchmark, based on historical US market data.
Your FIRE number
$1,250,000
The portfolio size needed to sustain your expenses at your chosen withdrawal rate.
How to use this fire number calculator
- 1Annual expenses in retirement: what you expect to actually spend per year once retired, not your current income — these can differ significantly.
- 2Safe withdrawal rate: 4% is the traditional benchmark (from the 'Trinity Study' of historical US market returns), though many FIRE planners now use 3.5% for a more conservative margin, especially for very long retirements.
Understanding your results
Your FIRE number is the portfolio size that, at your chosen withdrawal rate, sustains your annual expenses indefinitely (in theory) without depleting the principal on average, based on historical market returns. The conservative and aggressive comparisons show how sensitive this number is to your withdrawal rate assumption — a small change in rate produces a large change in the target.
The formula
FIRE number = Annual expenses ÷ Safe withdrawal rateThis is the inverse of the withdrawal rate itself: a 4% withdrawal rate means your expenses should be 4% of your portfolio, so your portfolio needs to be 25 times your annual expenses (1 ÷ 0.04 = 25). A lower, more conservative withdrawal rate requires a larger portfolio for the same spending level, since you're taking a smaller slice each year.
A worked example
$50,000 in annual expenses at a 4% withdrawal rate requires a $1,250,000 portfolio (25× expenses). At a more conservative 3.5% rate, the same spending requires about $1,428,600 — roughly $178,600 more, illustrating how much a 0.5-percentage-point difference in withdrawal rate assumption moves the target.
Notes for the UK, US and India
The 4% rule comes from historical US stock/bond portfolio data over rolling 30-year retirement periods — it's a reasonable starting benchmark, not a guarantee, and doesn't account for taxes, sequence-of-returns risk near retirement, or retirements meaningfully longer than 30 years (common in the FIRE community, which often targets retirement decades earlier than a traditional 65).
Frequently asked questions
Is the 4% rule guaranteed to work?+
No — it's based on historical US market data over rolling 30-year periods and worked in the vast majority of those periods, but past performance doesn't guarantee future results. Many FIRE planners use a lower rate (3-3.5%) for extra safety margin, especially for retirements longer than 30 years.
Does this account for Social Security or a pension?+
No — this calculates the portfolio needed to cover your full expenses from investments alone. If you'll also have Social Security or a pension, your required FIRE number is smaller — subtract the portion those sources will cover from your annual expenses first.
Should annual expenses include taxes?+
Yes, ideally — your real spending need should include any taxes owed on withdrawals, which vary by account type (traditional vs. Roth) and jurisdiction. Underestimating this is a common FIRE-planning mistake.