Coast FIRE Calculator
Find the amount you need invested today so that, with no further contributions, it grows into full retirement savings by your target age.
How it works
FIRE number = spending ÷ withdrawal rate · Coast number = FIRE number ÷ (1 + real return)^(retirement age − current age)
Coast FIRE is the point where your existing investments, left untouched, will compound into a full retirement nest egg by your target age. Once you reach it you no longer have to save for retirement — you only need to cover current expenses — because time and compounding do the rest. It is the discounted present value of your future FIRE number, so the more years you have, the smaller the amount you need today.
Worked example
A 30-year-old wanting $1,000,000 (from $40,000 spending at 4%) by age 65 has 35 years of growth. At a 5% real return the Coast FIRE number is 1,000,000 ÷ 1.05^35 ≈ $181,000. With $90,000 saved they are about halfway to being able to stop saving for retirement.
Frequently asked questions
How is Coast FIRE different from FIRE?
Full FIRE means you can stop working entirely. Coast FIRE means you can stop saving for retirement while still working to cover today’s bills — your invested money will grow into your retirement target on its own by the age you set.
Why does a younger person need less?
Compounding has more years to work, so a smaller sum today reaches the same future value. Reaching Coast FIRE at 30 might take $181,000, while at 45 the same goal could require well over $400,000.
What return should I assume?
Use a real (after-inflation) return so both the target and the coast number stay in today’s dollars. Many people model 5% real for a diversified stock-heavy portfolio, then revisit as markets and their timeline change.
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Educational estimate, not financial or tax advice. Rules and limits change — confirm current figures with a qualified advisor.