Coast FIRE Target Amount
Calculate the lump sum needed today so compound growth alone covers your retirement target using Google Sheets formulas.
=retirement_target / (1 + return_rate)^years_to_retirement How It Works
Coast FIRE is the point where your existing investments - with no further contributions - will grow to your retirement target through compound returns alone. This formula calculates that threshold by working backward from your goal.
Syntax
=retirement_target / (1 + annual_return)^years_to_retirementThis is a present value calculation - what a future amount is worth today given expected growth.
Example
Situation:
- Retirement Target: $1,200,000
- Expected Annual Return: 7%
- Years to Retirement: 25
Formula: =1200000 / (1 + 0.07)^25
Result: $221,042 needed today
If you already have $221,042 invested, compound growth at 7% handles the rest.
Coast FIRE Targets by Age
Assuming a $1,200,000 retirement target at age 65 with 7% returns:
| Current Age | Years to 65 | Coast FIRE Target |
|---|---|---|
| 25 | 40 | $80,172 |
| 30 | 35 | $112,427 |
| 35 | 30 | $157,674 |
| 40 | 25 | $221,042 |
| 45 | 20 | $310,073 |
| 50 | 15 | $434,737 |
Variations
With Monthly Compounding
For a more precise calculation using monthly compounding:
=retirement_target / (1 + annual_return/12)^(years * 12)Using Google Sheets PV Function
=PV(annual_return, years_to_retirement, 0, -retirement_target)The result is how much you need invested right now.
Setting Up a Coast FIRE Calculator
| A | B |
|---|---|
| Retirement Target | $1,200,000 |
| Expected Return | 7% |
| Years to Retirement | 25 |
| Coast FIRE Number | =B1/(1+B2)^B3 |
| Current Portfolio | $180,000 |
| Gap to Coast FIRE | =B4-B5 |
Pro Tips
-
Use real returns - subtracting inflation (often around 3%) gives a more realistic target
-
This is a moving target - your Coast FIRE number drops every year as you get closer to retirement
-
Once you coast, you still need income - Coast FIRE means you can stop saving, not stop working
-
Conservative estimates help - using 5-6% instead of 7% adds a buffer for market downturns
Common Errors
- Confusing nominal and real returns - 7% nominal minus 3% inflation is roughly 4% real return
- Forgetting the retirement target changes with inflation - $1.2M today may need to be $2M+ in 25 years
- Assuming constant returns - actual market returns vary year to year, so think of this as an estimate