Coast FIRE means your current investments are already enough: with zero further contributions they grow to your full FIRE number by your target retirement age. Find your coast point below, this is also searched as the coastfire calculator.
Sources & assumptions: the withdrawal-rate convention comes from William Bengen's 1994 paper “Determining Withdrawal Rates Using Historical Data” and the 1998 Trinity Study (Cooley, Hubbard & Walz), which tested inflation-adjusted withdrawals against US market history since 1926. The default 6% real return is a planning assumption, long-run US equity real returns have historically averaged roughly 6–7% per year (Dimson, Marsh & Staunton, Credit Suisse Global Investment Returns Yearbook), adjust it to your own outlook. Everything is in today's dollars; taxes, fees and sequence-of-returns risk are not modeled. All math runs in your browser and nothing you type leaves your device.
| Input | Result |
|---|---|
| Age 30→65 · $50k invested · $40k/yr spending · $500/mo | Coast number $130,105 · coast point at age ~37 |
| Age 25→60 · $80k invested · $50k/yr spending · $800/mo | Coast number $162,632 · coast point at age ~30 |
| Age 40→65 · $300k invested · $40k/yr spending | Coast number $232,999 · already coasting ✓ |
Coast FIRE is the point where your invested portfolio is large enough that, with no further contributions, compound growth alone carries it to your full FIRE number by your target retirement age. After reaching it you only need to cover current living costs, retirement saving is effectively done.
First compute the FIRE number: annual retirement spending divided by your safe withdrawal rate (at 4% that is 25× annual spending). Then discount it back to today by dividing by (1 + real return) raised to the years until retirement. The result is the portfolio you need invested today to be coasting.
Use a real (after-inflation) return so everything stays in today's dollars. Long-run US stock market real returns have historically averaged roughly 6–7% per year (Dimson, Marsh & Staunton, Credit Suisse Global Investment Returns Yearbook), so this calculator defaults to a conservative 6%. Lower it if you hold more bonds or want more margin of safety.
From William Bengen's 1994 paper and the 1998 Trinity Study (Cooley, Hubbard and Walz), which found that a 4% initial withdrawal adjusted for inflation survived virtually all historical 30-year US retirements. For retirements much longer than 30 years, many planners use 3.25–3.5% instead.
'Coastfire' is just the one-word spelling of coast FIRE, the same idea. Barista FIRE is different: there you plan to keep some part-time income in semi-retirement, so the portfolio only needs to cover part of your spending.
Every FIRE flavour asks a different question. The classic number asks "how much do I need to live on?" Coast FIRE asks something narrower and earlier: "how much do I need banked so that ordinary market growth alone finishes the job?" Once your portfolio hits that size, contributing more is optional, compounding is now contributing what your paycheck used to. You still work, because today's bills still need covering; you just stop worrying about retirement savings forever.
Coast targets look modest next to full FIRE numbers because they are measured at today's age, not at retirement. The engine is the exponent: at a 6% real return, money multiplies about 10× over 40 years, 5× over 27 years, 2× over 12. So a 25-year-old who wants a $1.5m nest egg at 65 needs only about $146,000 banked today, the remaining 90% arrives without another deposit. The same target for a 45-year-old needs roughly $466,000 banked, because the exponent has shrunk to about 3×. That asymmetry is the entire pitch: the same coast number is dramatically cheaper the earlier you buy it.
Every coast calculation embeds a long-run real return, ours defaults to 6%. Cut it to 4% and a 25-year-old's $146,000 coast number becomes about $324,000. The calculator's job is to make that sensitivity visible: move the return and the age sliders and watch how much the coast point moves before you treat any single output as a plan. And note what coast FIRE does not promise, it covers retirement only. Today's living expenses still require today's income, which is what separates this from Barista FIRE, where part-time work covers current bills.
How this page is built and kept current. Written and fact-checked by the MoneyCalcsHub editorial team. We do not sell financial products and we accept no payment to change a result, the arithmetic on this page runs in your own browser from the numbers you type.
Official sources used on this page:
Source-dependent figures are reviewed when the cited issuer publishes an update. Worked examples show the formula applied to the listed inputs; interactive results are calculated in your browser.
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