Coast FIRE Calculator

What Coast FIRE really means

Coast FIRE isn’t really about a number — it’s about the day the pressure lifts. It’s the point where you’ve already invested enough that, even if you never add another dollar, compounding carries that balance up to your full retirement number by the time you retire. You still pay today’s bills out of what you earn. But the long, patient job of investing for retirement? Done. From here, you coast.

That matters because retirement money was never the point either. What it buys is the freedom to choose — a lower-stress job, fewer hours, a year off, a leap into something risky — without quietly wondering whether you’re stealing from your future self. Coast FIRE is the milestone that hands you those choices decades before full financial independence does. And you don’t earn it by being clever; you earn it by starting, then letting time do the heavy lifting.

How the number is built

The chart above works out two figures: your FIRE number (what you need at retirement) and your Coast FIRE number (what you need invested today to get there on autopilot). It starts from the same idea as the savings goal calculator, just run in a different direction.

Your FIRE number is your annual retirement spending divided by a safe withdrawal rate — 4% by default, the classic multiply-by-25 rule. Plan to spend $40,000 a year and that’s a $1,000,000 target. (Our guide to what FIRE and Coast FIRE are walks through where that 4% comes from and why it’s a guideline, not a law.)

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 seed, because compounding gets more time to work. That’s why the curve above starts low, stays flat on what you put in, and climbs on growth alone to meet the FIRE line — with zero further contributions the whole way.

Why it’s such a freeing milestone

Hitting Coast FIRE changes your options long before you’re rich. 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 work you actually like, going part-time, taking a career break, or betting on something of your own — the retirement piece is already handled. This is exactly what “Barista FIRE” describes: coasting while a lower-key job (with, say, health benefits) covers today’s expenses.

Two honest levers get you there faster, and neither is picking a hot stock. The first is grabbing free money: an employer 401(k) match adds to your balance before you’ve felt the pinch, so your seed grows without straining your budget. The second is simply starting — the sooner your money is invested, the more years it has to compound toward the line. And if your plan is eventually to live off that portfolio rather than sell it down, seeing how much you need to live off dividends is the same 4% idea from the income side. If Coast FIRE is new territory, the free 30-day path to financial foundations builds up from a budget to a safety net to compounding and FIRE, in order — so the milestone feels reachable instead of abstract.

A worked example

Say you’re 30, want to retire at 60, and expect to spend $40,000 a year at a 5% real return. Your FIRE number is $1,000,000, and your Coast FIRE number — the seed that grows to a million over 30 years at 5% — is about $231,377. Put that much in today, add nothing more, and compounding supplies the other $768,623 on its own. If you already have $231,377 invested, you’re coasting: you could stop retirement saving this year and still arrive on schedule. If you have less, the calculator shows the gap so you know exactly what you’re aiming at.

The two big levers — and why later is never too late

Two things move your coast number most: time and the size of the target. More years means compounding covers more, so the seed shrinks. A smaller retirement budget shrinks the FIRE number, which shrinks the seed too. A later start does raise the number — but it never removes it, and you have more than one lever to pull.

Take someone at 45, aiming to retire at 60 on $40,000 a year. From today, the Coast FIRE number is about $481,000 — genuinely steep. But that figure was never the only option:

If your earliest years are behind you, that’s not a reason to skip the next twenty — it’s the reason to plant the seed this month instead of next.

What this calculator does not do

Keep the assumptions honest. The model uses a single, steady real return and assumes your spending and plans stay roughly constant. Real markets are volatile, a rough early stretch changes outcomes, and life shifts. It also ignores taxes and fees, and it doesn’t include the money you’ll still need for today’s bills while you coast. If you’d rather fix a monthly contribution and see when a target arrives, when will I reach my goal times the same kind of milestone. Treat Coast FIRE as a motivating checkpoint, not a promise — and for decisions about your own finances, talk to a qualified professional.