Coast FIRE Calculator

How this is worked out

Coast FIRE is one idea: compound growth does not care whether you keep paying in. Once the pot is large enough that growth alone carries it to a full retirement fund by the date you want, every further contribution is optional.

It takes three steps.

The full fund. Yearly spending divided by the withdrawal rate. At 4%, spending of 30,000 a year needs 750,000.
Discount it back to today. Divide by (1 + real return)^years. That is the coast number — what you would need invested right now for growth alone to reach the full fund by your retirement date.
Compare it with what you hold. If you are above the line, you have already coasted. If not, the gap is what is still missing.

The return is a real return, after inflation, which is why the spending figure stays in today's money. Mixing the two — a nominal return against today's prices — is the most common way to get a wildly optimistic answer.

A worked example

120,000 invested at 34, retiring at 60, spending 30,000 a year, 4% withdrawal, 5% real return:

Full fund needed: 750,000
26 years of growth multiplies money by about 3.56
Coast number: 750,000 ÷ 3.56 = about 210,700
You hold 120,000, so the gap is about 90,700
Left alone, that 120,000 becomes about 427,000 by 60 — a little over half the target

Carry on saving until the pot passes 210,700 and, on these assumptions, you could stop contributing entirely and still land on 750,000 at 60.

What this doesn't cover

Coast FIRE is not retirement. It means contributions become optional, not that you can stop earning — you still need income for today's bills.
The answer is extremely sensitive to the assumed real return. Drop it from 5% to 3% and the coast number rises by roughly half. Run it both ways.
A single average return hides the sequence. Real markets do not deliver the same percentage every year, and a bad decade near the end matters far more than a bad decade near the start.
Tax, access rules and pension lock-in ages are ignored. Money inside a pension you cannot touch until 60 is not the same as money in a brokerage account, even when the balance is identical.

Common questions

What is the difference between Coast FIRE and normal FIRE?

FIRE is the full fund — enough to live on now. Coast FIRE is the smaller amount that grows into the full fund by a chosen date without further contributions. Reaching it means you can stop saving; reaching FIRE means you can stop working.

What real return should I assume?

Long-run global equity returns after inflation have often been quoted around 5%, and many people plan with 4% to 5% for a stock-heavy portfolio and less for a mixed one. Treat any single figure as a scenario, not a forecast, and always check how the plan looks at a lower one.

Why does the withdrawal rate matter so much?

Because it sets the size of the whole target. At 4% you need 25 times your yearly spending; at 3% you need 33 times. That difference flows straight through to the coast number.

Does this include the state or government pension?

No. If you expect a state pension, occupational pension or annuity, you could subtract its yearly amount from your spending figure before using this, which lowers the fund you need from your own savings.