Your FIRE number — and how much you need saved today to coast there.

What is a FIRE number?

Your FIRE number is the invested net worth needed to sustain your spending indefinitely using a safe withdrawal rate — most commonly the "4% rule," derived from the Trinity Study, which implies a FIRE number of 25× your annual expenses (1 ÷ 0.04 = 25). A lower withdrawal rate is more conservative and produces a higher FIRE number; a higher withdrawal rate is more aggressive and produces a lower one.

What is Coast FIRE?

Coast FIRE is the amount you'd need invested today such that, left alone with no further contributions, compound growth alone carries it to your full FIRE number by your target retirement age: Coast FIRE number = FIRE number ÷ (1 + return)^{years to retirement}. Once you've hit your Coast FIRE number, you can theoretically stop saving for retirement entirely and just cover current living expenses — though most people in practice keep contributing rather than literally stopping.

Is the 4% rule still considered safe?

It's genuinely debated. The original Trinity Study looked at 30-year US retirement horizons; retiring in your 30s or 40s implies a much longer horizon than that study modeled, which is why many in the FIRE community use a more conservative 3.25–3.5% withdrawal rate instead. Adjust the withdrawal rate field above to see how that single assumption moves your entire target.

Does this account for Social Security, pensions, or other income?

No — this calculates the FIRE number needed if your investment portfolio alone had to cover 100% of expenses. Any pension, Social Security, or other guaranteed income you'll eventually receive would reduce how much portfolio-funded spending you actually need, and therefore your real FIRE number — factor that in separately if it applies to you.

Worked example: $40,000/year in expenses at a 4% withdrawal rate gives a FIRE number of $1,000,000. At age 30 targeting retirement at 60 (30 years) with a 7% expected return, the Coast FIRE number today is about $131,367 — meaning $150,000 already saved at age 30 has already cleared Coast FIRE for this scenario.