Most Coast FIRE calculators ask for one number and hand you one answer. This one works through five income brackets with explicit assumptions, shows the math, and compares Coast FIRE against full FIRE so you can see what the trade-off really costs.
Full FIRE means saving 25× your annual expenses and never working again. Coast FIRE is the intermediate version: save enough now that compound growth alone carries you to your full retirement number by a conventional age — say 65 — so you can still work a job you don't hate, on a schedule you choose, without another contribution to the portfolio.
The definition sounds simple and hides three assumptions that change the answer more than anything else:
For each income level we assume a plausible savings rate, take the remaining spending as the annual retirement budget, multiply by 25 (the 4% safe-withdrawal convention), and discount that target 35 years at 7% to get the amount a 30-year-old would need in the account today.
| Annual income | Save rate | Retirement budget | Target at 65 | Coast number at 30 | Or save /mo for 5 yrs |
|---|---|---|---|---|---|
| $50,000 | 10% | $45,000 | $1,125,000 | $105,371 | $2,086 |
| $75,000 | 15% | $63,750 | $1,593,750 | $149,275 | $2,956 |
| $100,000 | 20% | $80,000 | $2,000,000 | $187,326 | $3,709 |
| $150,000 | 30% | $105,000 | $2,625,000 | $245,865 | $4,868 |
| $250,000 | 40% | $150,000 | $3,750,000 | $351,236 | $6,955 |
Reading the last column: it's the monthly contribution that accumulates to the coast number over 60 months at 7% — a useful benchmark for "how aggressive does my saving need to be." For the $100k bracket, $3,709/mo for five years is the price of coasting for the next 35.
A $250k earner who saves 40% and spends $150k a year needs $351k to coast — 3.3× the $105k needed by the $50k earner. Income alone tells you nothing. Two people with identical salaries can have coast numbers that differ by 2×, purely on lifestyle. If you're early in your career, the highest-leverage decision you can make is not which fund to buy — it's keeping the spending side of that ratio under control.
Notice the last column requires saving at 20–40% of income for a concentrated five years. That's the trade: you compress the effort into a window where your career cash flow is building, then stop. The alternative — full FIRE at $100k income with a 20% savings rate — takes 31 years of never-stopping contributions to reach $2,000,000. Coast FIRE converts 31 years of grinding into 5 years of intensity and 30 years of optionality. Neither is objectively better; they're different risk profiles. The coast profile bets on 35 years of market survival; the full profile bets on 31 years of your own discipline.
Every number above inherits the 4% safe-withdrawal assumption, which comes from a specific historical US equity drawdown pattern. If you expect a worse sequence — the 1970s, for instance — practitioners often quote 3%–3.5%, which would raise every coast number in the table by roughly 40–65%. The table is the base case, not a ceiling.
Find your row. If the coast number is within reach of a 3–5 year save burst, Coast FIRE is a legitimate strategy — not a consolation prize. If it's 3× your current net worth and your income isn't on a steep climb, the honest answer is usually "full FIRE later" rather than "coast now and hope." Either way, the number you should be tracking is not your salary. It's the gap between your current savings and the number in your row, divided by your remaining runway.
Run your own numbers with our Coast FIRE Calculator — it takes your actual age, target age, and savings rate instead of the assumptions above.
CalcClear.com provides educational tools and general information. Nothing on this site is financial, investment, or tax advice. Assumptions in this guide (7% real return, 4% withdrawal rate, 35-year runway) are illustrative, not predictions. Consult a qualified professional before making financial decisions.