Coast FIRE Calculator
Find your Coast FIRE number — the portfolio that, left untouched, grows into full financial independence by your target retirement age.
How to use this tool
- Enter your expected annual retirement spending in today's dollars.
- Set your safe withdrawal rate (4% is the standard 25× rule).
- Enter your current age and your target retirement age.
- Add your current invested assets and an expected real (after-inflation) return.
- Read your Coast FIRE number and whether your current savings already cover it.
Coast FIRE is the milestone where your investments can coast to full retirement on their own. Enter your numbers to see the portfolio you'd need today and whether you've already reached it.
Formula
Full FIRE number = Annual expenses ÷ (Withdrawal rate ÷ 100) (the 25× rule at 4%).
Coast FIRE number = FIRE number ÷ (1 + r)n, where r is the expected real annual return and n = target retirement age − current age.
Projected balance = Current invested assets × (1 + r)n. You have reached Coast FIRE when your current assets are at or above the Coast FIRE number.
How it works
Coast FIRE describes the moment when your invested assets are large enough that, even if you never contribute another dollar, ordinary market growth will carry them to your full financial-independence target by your chosen retirement age. After that point you only need to earn enough to cover current living costs — the heavy lifting is done.
This calculator first derives your full FIRE number from the safe-withdrawal rate (the inverse of the rate; 4% implies 25× annual expenses), then discounts that target back to today using compound growth over the years remaining until retirement. We use a real (inflation-adjusted) return so the result stays in today's dollars, which keeps the expense input and the answer on the same footing.
The model assumes a single, constant return and no future contributions — deliberately simple so the Coast FIRE threshold is transparent. Real markets are volatile and sequence-of-returns risk matters near retirement, so treat the projection as a planning guide rather than a guarantee. Reviewed by the AbraCalc Retirement Desk against the standard compound-growth and 4%-rule conventions.
Worked example
Age 35, retiring at 65, $135k invested, 7% real return
- Full FIRE number = $40,000 ÷ 0.04 = $1,000,000.
- Years to grow: n = 65 − 35 = 30.
- Growth factor = (1 + 0.07)30 = 7.612255.
- Coast FIRE number = $1,000,000 ÷ 7.612255 = $131,367.12.
- Your $135,000 ≥ $131,367.12, so Coast FIRE is reached and the gap is $0.
- Projected balance at 65 = $135,000 × 7.612255 = $1,027,654.43.
Coast FIRE number: $131,367.12 — reached (gap $0), projected $1,027,654.43 at retirement.
Coast FIRE number by current age (4% rule, 7% real return, retire at 65)
| Current age | Years to grow | Coast FIRE number (for $1,000,000 FIRE target) |
|---|---|---|
| 25 | 40 | $66,780 |
| 30 | 35 | $93,663 |
| 35 | 30 | $131,367 |
| 40 | 25 | $184,249 |
| 45 | 20 | $258,419 |
| 50 | 15 | $362,446 |
| 55 | 10 | $508,349 |
| 60 | 5 | $712,986 |
Key terms
- Coast FIRE
- The point at which existing investments will grow to your full FIRE number by retirement age with no further contributions.
- FIRE number
- The portfolio size that funds your retirement spending at your chosen withdrawal rate — typically 25× annual expenses at 4%.
- Real return
- Investment return after subtracting inflation; using it keeps both your expenses and your target in today's dollars.
- Barista FIRE
- A related milestone where part-time or lower-stress work covers current expenses while a Coast FIRE portfolio grows untouched.
Frequently asked questions
- What is Coast FIRE?
- Coast FIRE is the amount you need invested today so that, with no further contributions, normal market growth reaches your full FIRE number by retirement age. Once you hit it, you only need to cover current expenses.
- How is the Coast FIRE number calculated?
- Take your full FIRE number (annual expenses ÷ withdrawal rate) and discount it back to today over the years until retirement using your expected real return: FIRE ÷ (1 + r)^n.
- What return should I use?
- Use a real, after-inflation return so your answer stays in today's dollars. A diversified stock portfolio has historically returned roughly 7% real; use a lower figure to be conservative.
- Does this include future contributions?
- No. Coast FIRE is specifically the point where no further contributions are required. The projection assumes you stop contributing and let the portfolio grow.