Coast FIRE explained

Coast FIRE is the balance that could reach your FIRE number by a chosen age if you stopped contributing and the assumed real return held. You may still need a paycheck for living expenses. You no longer need one to feed the portfolio.

Arc · Published September 18, 2026 · Updated September 18, 2026

Use a real return if the FIRE number is in today's dollars. A nominal return plus an inflating target is a different model. Do not mix them.

Coast number = FIRE number ÷ (1 + real return) ^ years

Example

FIRE number $2,000,000, 20 years away, 5% real return. The coast number is $2,000,000 ÷ 1.05^20, about $754,000. If the portfolio is already there, new contributions are optional under that assumption. Spending still has to come from work or from other income until you actually stop.

What coasting does not mean

It does not mean you can quit. It does not survive a lower return, a higher future spending number, or a decision to retire sooner. Recalculate when any of those change.

Common questions

How is Coast FIRE different from the FIRE number?

The FIRE number is the portfolio at the point you stop working. The coast number is the smaller portfolio today that might grow into that FIRE number with no further contributions.

Sources

Bengen, William P. “Determining Withdrawal Rates Using Historical Data.” Journal of Financial Planning, 1994.