Coast FIRE by Age Calculator
Find the portfolio you need at your current age so that, with zero further contributions, it grows into your full FIRE number by retirement.
How it works
FIRE number = annual expenses ÷ SWR · Coast number = FIRE number ÷ (1 + real return)^(retire age − current age)
Coast FIRE is the point where your invested savings are large enough to grow — on their own, with no new contributions — into a full retirement nest egg by your target age. You still work to cover current expenses, but you no longer need to save for retirement. The younger you are, the more years of compounding you get, so the coast number is a small fraction of the full FIRE number.
Worked example
A 30-year-old wanting $40,000/year at a 4% withdrawal rate needs a $1,000,000 FIRE number. With 35 years of 5% real growth, money multiplies 5.52×, so they only need $1,000,000 ÷ 5.52 = about $181,000 invested today to coast.
Frequently asked questions
What is the difference between Coast FIRE and full FIRE?
Full FIRE means your portfolio already covers your expenses and you can stop working. Coast FIRE means your portfolio is big enough to grow into that full number by retirement without new contributions — you still work to pay today’s bills, but retirement is already funded.
Why does age matter so much?
Compounding is exponential, so each extra year of growth shrinks the amount you need today. A 25-year-old needs far less than a 45-year-old to hit the same retirement target, because their money has more time to multiply.
What real return should I assume?
A 4–6% real (after-inflation) return is a common long-run assumption for a diversified stock-heavy portfolio, but it is not guaranteed. Lower it to be conservative and recompute.
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Educational estimate, not financial advice.