Coast FIRE is the moment you have enough already invested that, without adding another cent, compounding alone will grow it to your full retirement number by the time you retire. You still need to cover today's expenses, but you no longer have to invest for retirement.

How is the Coast FIRE number calculated?

First we find your FIRE number — your annual retirement expenses divided by your withdrawal rate (4% by default, i.e. expenses × 25). Then we discount that back to today using your expected return and years to retirement. The result is the amount that, left alone, grows into your FIRE number.

What return should I use?

Use a real (after-inflation) return, since your expenses are in today's dollars. A common long-run assumption for a diversified stock portfolio is around 5% real, but it is not guaranteed and you should test lower numbers too.

What is the difference between Coast FIRE and regular FIRE?

Regular FIRE means you have the full amount to live off investments now. Coast FIRE means you are on track to have it by retirement without further contributions — a much smaller, earlier milestone that takes the pressure off.

Coast FIRE Calculator

Find out how much you need invested today so you can stop contributing and still hit your retirement number — the point where compounding coasts you to financial independence.

What Coast FIRE means

Coast FIRE is one of the most freeing milestones in personal finance. It is the point where you have already invested enough that, even if you never add another dollar, compounding will carry that balance up to your full retirement number by the time you retire. You still have to pay today’s bills, but the heavy lifting of investing for retirement is done — you can “coast.”

The calculator above works out two numbers: your FIRE number (what you need at retirement) and your Coast FIRE number (what you need invested today to get there on autopilot). Enter your age, when you want to retire, your expected annual expenses in retirement, and a realistic return, and it shows whether you are already coasting or how far away you are.

How the number is built

It starts from the same idea as the savings goal calculator, just run in a different direction. Your FIRE number is your annual expenses divided by a safe withdrawal rate — 4% by default, which is the classic “multiply by 25” rule. If you plan to spend $40,000 a year, that is a $1,000,000 target.

Then we discount that target back to the present. Because money grows by compounding, a smaller amount today becomes your full FIRE number after enough years — the same compound interest engine, viewed as “what seed grows into this tree?” The longer you have until retirement, the smaller the Coast FIRE number, because compounding has more time to work.

Why it is such a powerful milestone

Hitting Coast FIRE changes your options long before full financial independence. Once your invested balance is coasting toward retirement on its own, you only need to earn enough to cover current living costs. That can mean switching to a lower-stress job, going part-time, taking a career break, or starting something risky — the retirement piece is already handled. This is why variations like “Barista FIRE” (coasting while a part-time job covers expenses) are built on the same idea.

A worked example

Say you are 30, want to retire at 60, and expect $40,000 a year in retirement at a 5% real return. Your FIRE number is $1,000,000, and the Coast FIRE number — the amount that grows to a million over 30 years at 5% — is a little over $231,000. If you already have that invested, you are coasting: you could stop retirement investing today and still arrive on schedule. If you have less, the calculator shows the gap.

What it does not account for

The model uses a single, steady real return and assumes your expenses and plans stay roughly constant. Real markets are volatile, a bad early stretch changes outcomes, and life plans shift. It also does not include money you will still need for today’s expenses. Treat Coast FIRE as a motivating checkpoint and a planning tool — not a guarantee — and speak with a qualified professional for decisions about your own finances.