Coast FIRE Calculator
How much you need invested today so that, without adding another cent, it grows into your FIRE number by the age you want to retire.
Results
The dashed line marks the value you entered.
What this tool does
Coast FIRE is the point where retirement saving is done: from then on, work only has to pay the current bills while compound growth finishes the job. The target is your FIRE number, annual spending divided by a safe withdrawal rate (the 4 % rule comes from William Bengen's 1994 study and the later Trinity study), discounted back to today. Use a real return, after inflation, because the spending is in today's money. The result is very sensitive to that return: over 30 years, assuming 4 % instead of 5 % raises the coast number by about a third. It also assumes you never touch the money, so revisit it every year or two.
Formula
FIRE number = spending ÷ withdrawal rate · Coast number = FIRE number ÷ (1 + r)ⁿ
Variables
| Symbol | Meaning | Unit |
|---|---|---|
ae | What you spend in a year | — |
wr | Safe withdrawal rate | % |
rr | Expected return after inflation | % |
ca | Your age now | a |
ra | Age you want to retire | a |
cs | Current savings | — |
CN | Coast FIRE number (needed today) | — |
FN | The number you need | — |
GP | Still missing to coast | — |
PV | Today's savings at retirement age, if left alone | — |
AC | Age at which today's savings alone reach the FIRE number | a |
ST | Where you stand | — |
Worked example
- What you spend in a year30,000
- Safe withdrawal rate4 %
- Expected return after inflation5 %
- Your age now30 a
- Age you want to retire60 a
- Current savings80,000
- Coast FIRE number (needed today)173,533
- The number you need750,000
- Still missing to coast93,533
- Today's savings at retirement age, if left alone345,755
- Age at which today's savings alone reach the FIRE number75.9 a
- Where you standNot yet: keep investing
Limitations
- This is an informational calculator, not personalised financial advice. Rates, fees, taxes and contract conditions vary between institutions and countries.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.