Coast FIRE Formula: How to Calculate Your Coast FIRE Number
Coast FIRE means your current investments can grow to your future retirement target by your planned retirement age without more retirement contributions. You still need income for current expenses, but your retirement portfolio is expected to compound on its own.
Quick Answer
The Coast FIRE formula estimates how much you need invested today so your portfolio can grow to your full retirement number by your target retirement age. It divides your future FIRE number by your expected compound growth over the years remaining until retirement.
The Coast FIRE Formula
Real return is your expected investment growth after inflation and investment fees. If you expect 8% annual growth, 3% inflation, and 0.2% fees, the calculator uses about 4.8% real return.
| Term | Meaning |
|---|---|
| Annual retirement spending | Expected yearly spending in retirement. |
| Safe withdrawal rate | The percentage you plan to withdraw each year. |
| Years until retirement | Target retirement age minus current age. |
| Real return | Investment return after inflation and fees. |
Worked Example
If annual retirement spending is $60,000 and the withdrawal rate is 4%, the FIRE number is $1,500,000. If you are 35, plan to retire at 65, and use a 5% real return, the Coast FIRE number is about $347,000.
FAQ
Can I calculate Coast FIRE manually?
Yes. Calculate your FIRE number first, then discount it back by your real return over the years left until retirement.
Should I use nominal or real return?
Use real return for Coast FIRE planning because it adjusts the result for inflation and fees.
Educational content only. Not financial, investment, tax, or retirement advice.