Coast FIRE Calculator

What is Coast FIRE?

Coast FIRE (Financial Independence, Retire Early) is the point where your existing investments are large enough that compound growth alone will carry them to a full retirement pot by your target retirement age — with zero further contributions. Once you cross it, saving for retirement becomes optional. You still work to pay the bills, but every dollar of pressure to “save more” disappears: the portfolio finishes the job by itself.

That makes Coast FIRE the most achievable milestone on the FIRE spectrum. You don't need the $1.5m+ pot that full early retirement demands — you need a much smaller amount, early. Time does the heavy lifting: money invested at 30 has 35 years to compound before a typical retirement at 65.

How this calculator works

Enter six things and the calculator answers three questions instantly, right in your browser:

• Your Coast FIRE number today — the pot that, growing untouched at your assumed real return, becomes your full FIRE number by retirement age.
• Whether you've already coasted — a progress bar shows how far along you are, and the shortfall if you haven't.
• Your coast age — if you keep contributing at your current rate, the age at which you cross the coast line. The chart marks the exact crossing point, and the shareable link preserves your whole scenario.

Everything is computed in today's money: the growth rate you enter is deflated by your inflation assumption, so results are directly comparable to today's prices. Nothing you type is sent to a server — the math runs entirely on your device.

The Coast FIRE formula

Two steps. First, the classic FIRE number from your desired spending and a safe withdrawal rate (SWR):

Then discount it back from retirement age to your age today using the real (after-inflation) return:

Worked example: spending of $60,000 a year at a 4% withdrawal rate needs a FIRE number of $1,500,000. With 7% nominal growth and 3% inflation (≈3.9% real), a 30-year-old retiring at 65 needs only about $395,000 today to coast. The other $1.1m? Compounding builds it.

Coast FIRE numbers by age

Using the same defaults ($60,000 spending, 4% SWR, 7% growth, 3% inflation, retire at 65), here's roughly what you'd need invested at each age to be coasting already:

Notice the pattern: every five years you wait, the bar rises by roughly a quarter. That's the whole argument for front-loading retirement savings in your 20s and 30s.

Coast FIRE vs Barista, Lean & Fat FIRE

401(k), IRA or taxable — where should coast money live?

Coast FIRE doesn't care which account your money sits in, but taxes do:

• 401(k) with employer match: take the full match before anything else — it's an instant 50–100% return. Penalty-free access normally begins at 59½.
• Roth IRA: contributions (not earnings) can be withdrawn any time, making Roth money a flexible piece of an early-retirement plan; qualified growth is tax-free.
• Taxable brokerage: no limits and no lock-ins — long-term capital gains rates apply. This is what funds the years before 59½ if you retire very early.

A common Coast FIRE pattern: max the match, fill the Roth, then let the whole pot coast while you downshift careers.

Choosing your assumptions (the honest version)

Your coast number is only as good as three inputs:

• Real return: global equities have historically returned roughly 5% after inflation over long horizons; 7% nominal with 3% inflation (≈4–4.5% real) is a reasonable planning default, and dropping to 3.5–4% real gives you margin for bad decades.
• Withdrawal rate: 4% is the classic US rule of thumb; longer retirements and cautious planners favour 3–3.5%. Small changes move the answer a lot — that's why the slider exists.
• Spending: the single most powerful lever. Every $1,000 of annual retirement spending you trim removes roughly $25,000 (at 4%) from your FIRE number — and shrinks your coast number with it.

Five ways to reach your coast number faster

1. Front-load ruthlessly. Money invested this year compounds for every remaining year — the table above shows the bar rising ~25% for every five years of delay.
2. Capture every match. Employer contributions are part of your coast pot too, and they're free.
3. Cut investment fees. A 1% platform-plus-fund fee is a ~20% lifetime haircut on a coast portfolio. Broad index funds under 0.2% keep compounding for you, not your platform.
4. Bank your raises. Direct half of every pay rise to investments before lifestyle absorbs it — your savings rate climbs without feeling poorer.
5. Re-test yearly, not daily. Coast status wobbles with markets. Check once a year with fresh numbers; act on trends, not headlines.

Frequently asked questions

Disclaimer: This page is educational content, not personalised financial advice. Projections use constant returns and ignore taxes, fees and sequence-of-returns risk unless stated. Consider speaking to a regulated financial adviser before making retirement decisions.