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Coast FIRE Calculator

Coast FIRE is the point where the money you already have invested will grow into your full retirement number on its own, even if you never add another dollar. Enter your ages and savings to see your Coast FIRE number today and the age you can stop saving.

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In today's dollars. Leave out what a pension or Social Security will pay.

%

The 4% rule is the usual starting point.

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$
%

An assumption, not a promise. Lower it to be safe.

Your Coast FIRE number today$181,290You're $81,290 short. Adding $10,000 a year, you can stop saving at age 41.
  • Invested now$100,000
  • Still to go$81,290
FIRE number at retirement (spending ÷ 4%)
$1,000,000
Years until retirement
35
Coast FIRE number today (grows 5% a year)
$181,290
Invested savings now
$100,000
Still to go
$81,290
Age you can stop saving
41

Coasting means you stop adding to this money, not that you stop working: your pay still has to cover your spending until you retire. All amounts are in today's dollars and assume one steady return.

How Coast FIRE works

First find your FIRE number: yearly spending in retirement divided by your withdrawal rate. Then work backward. Your Coast FIRE number is the amount that, growing at your expected return, reaches the FIRE number by the age you retire. Once your savings pass it, your job only has to pay your bills until then.

The formula is FIRE number ÷ (1 + return) raised to the years until retirement. Because it uses a return after inflation, every figure is in today's dollars.

A worked example

A 30-year-old plans to retire at 65 and spend $40,000 a year. At a 4% withdrawal rate the FIRE number is $40,000 ÷ 0.04 = $1,000,000. At a 5% return after inflation, money grows about 5.52 times over 35 years, so the Coast FIRE number today is $1,000,000 ÷ 5.52 = $181,290.

With $100,000 invested they are $81,290 short. Adding $10,000 at the end of each year, they cross the line after 11 years and can stop saving for retirement at 41.

Where the 4% rule comes from

A 1998 study in the AAII Journal, often called the Trinity study, tested withdrawals against market returns from 1926 to 1995, raising each year's withdrawal with inflation. Over 30-year retirements a 4% rate lasted in 95% to 98% of past periods for portfolios with at least half in stocks. If your retirement could run longer than 30 years, a lower rate is the safer choice.

Questions

What is a Coast FIRE number?

It is the amount you need invested today so that, with no more contributions, it grows to your full FIRE number by your retirement age.

What happens after I reach Coast FIRE?

You can stop adding to your retirement savings and leave them invested. You still need income from work to pay your living costs until you retire.

Why does the number shrink when I'm younger?

Money invested earlier has more years to compound. Thirty-five years at 5% multiplies it about 5.5 times, so you need far less today than at 55.

Should I use a real or nominal return?

Use a real return, meaning after inflation. That keeps the FIRE number in today's dollars so you can compare it with what you spend now.

Is Coast FIRE the same as Barista FIRE?

No. Coast FIRE means your savings can grow untouched while work pays your bills. Barista FIRE means you start withdrawing early and part-time income covers the rest.

What if markets do worse than I assume?

Then you would fall short at retirement. Many people keep saving a little past their coast point or use a lower return to build in a cushion.

Sources

Updated November 3, 2026. Estimates only, not tax or financial advice.

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