What is a FIRE number and how do I calculate mine?
Your FIRE number is 25× your annual spending — the portfolio size where a 4% withdrawal covers your expenses indefinitely. If you spend $50,000/year, your FIRE number is $1,250,000. It's the threshold for financial independence.
Formula
FIRE Number = Annual Spending × 25
Example
$50k spending → $1.25M FIRE number. $80k spending → $2M. $120k spending → $3M. At a 50% savings rate on $100k income, you'd reach $1.25M in roughly 17 years.
How it works in detail
FIRE stands for Financial Independence, Retire Early. Your FIRE number is not based on income — it's based on spending. Two people earning $200,000 can have wildly different FIRE numbers if one spends $60k and the other spends $150k. There are variants: LeanFIRE ($40k or less spending), regular FIRE ($40–100k), and FatFIRE ($100k+). Coast FIRE means you've saved enough that compound growth alone will reach your FIRE number by traditional retirement age, even without further contributions.
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How much do I need to retire?
Multiply your annual spending by 25. If you spend $60,000/year, you need $1,500,000. This is the 4% rule from the Trinity Study (1998) — withdraw 4% annually with a 95%+ historical success rate over 30 years.
What is Coast FIRE and how much do I need?
Coast FIRE is the invested balance today that will compound to your FIRE number by retirement age without any additional contributions. If your FIRE number is $1.5M and you're 30 with a 7% real return, you need $194,000 today to coast — meaning you only need to earn enough to cover current expenses.
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