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Coast FIRE Calculator

See the savings that let you stop contributing and still retire.

How it is calculated

The tool discounts your retirement target back to today at an assumed constant yearly return: coast number = target ÷ (1 + annual_return ÷ 100)years. The target is the portfolio value you want at retirement in dollars, the return is a yearly percentage (7 means 7%) and years is the time until you retire; fractional years such as 10.5 work in the formula, although the echoed line rounds them to a whole number. If the portfolio you already hold is at least the coast number, then with no more contributions, and if the assumed return holds, it would grow to the target. With zero years or a zero return the answer is the target itself. A negative target, negative years or a return of −100% or lower gives no result. The maths is a single compounding step: it ignores inflation, taxes, fees and market volatility, and the return you enter is applied smoothly every year, which real markets do not do. Treat it as an estimate.

Worked example

You want 1,500,000 at retirement, 30 years away, and assume a 7% yearly return. The growth factor is 1.0730, about 7.612. Dividing, 1,500,000 ÷ 7.612 gives the coast number. The tool prints $197,050.68. If you already have that much invested, letting it compound at 7% for 30 years would reach about 1,500,000 without another contribution, though you would still pay living costs from income.

Try this example →

Common mistakes

  • Using a nominal return against a target in today's money. If the target is meant to buy what 1,500,000 buys now, enter a return after inflation, or the coast number will be too low.
  • Typing the return as a decimal. Enter 7 for 7%; 0.07 means 0.07% and makes the coast number almost equal to the target.
  • Entering years as the number of years you have already saved rather than the years left until retirement.
  • Assuming you can stop working once you reach the number. Coast FIRE only means the retirement portfolio is on track; income must still cover current living costs.
  • Entering a return of −100% or lower, or negative years. These are impossible, so the tool shows no result instead of a number.

About this calculator

Coast FIRE is the point at which you have enough already invested that, left alone to grow through compound returns with no further contributions, it will reach your full retirement number by your target retirement age. Once you hit it, you can theoretically stop saving for retirement entirely — you'd still need income to cover current living expenses, but you'd be “coasting” to retirement on compounding alone.

This calculator takes your target retirement number, your investment horizon, and an assumed rate of return, and works backward to the amount you'd need saved right now to coast the rest of the way. It's used by people who want to shift career priorities — working less, taking a lower-paying but more enjoyable job, or reducing hours — without derailing their eventual retirement.

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