Coast Number Needed Today Calculator
Find the amount you’d need invested today so that, with no more contributions, it grows into your full retirement number by the age you choose.
How it works
FIRE number = spending ÷ withdrawal rate · Coast number = FIRE number ÷ (1 + r)^years
Coast FIRE is the point where your invested savings are large enough to grow into your full retirement target on their own, with no further contributions. It is simply the retirement number discounted back to today at your expected return. Reaching it does not mean you can stop working — you still need income for living costs — but you can stop saving for retirement and redirect that money elsewhere.
Worked example
Someone aged 30 wanting to retire at 65 on $40,000 a year needs a $1,000,000 nest egg at a 4% withdrawal rate. Over 35 years at a 5% real return, money multiplies about 5.5×, so the coast number today is 1,000,000 ÷ 5.5 ≈ $181,000. Hit that, and compounding alone finishes the job.
Frequently asked questions
How is Coast FIRE different from regular FIRE?
Full FIRE means you have the entire nest egg now and can stop working. Coast FIRE means you have enough invested that it will grow into the nest egg by your retirement age without more saving — you still work to cover current expenses, but retirement is already funded.
Why does the coast number rise as I get older?
Fewer years until retirement means less time for compounding, so a larger sum is needed today to reach the same target. A 25-year-old needs far less than a 45-year-old for the identical retirement number.
What return should I assume?
Use a conservative real (after-inflation) return — many people use 4–6%. A higher assumed return shrinks the coast number, but if markets underperform you may fall short, so err on the cautious side.
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This is an educational estimate, not financial advice. Real results depend on rates, taxes, fees and market returns that no calculator can guarantee — confirm figures with your lender or a licensed advisor.