Convert retirement spending into a portfolio target with a withdrawal rate you understand.
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Full FIRE Number
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Your target at retirement
| Age Now | Coast FIRE Number | Years to Grow |
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Coast FIRE by Age — Financial Depth
financialdepth.com/coast-fire-by-age
Quick Summary (TL;DR)
- Coast FIRE number = your full FIRE number discounted to today by your return.
- The younger you are, the smaller it is — compounding does the rest.
- Example: $40k expenses, retire 65, 7% real → about $130k at age 30.
- You still need income for current expenses until retirement.
Why Your Coast Number Shrinks With Age
Coast FIRE is the moment you have enough invested that, even with zero further contributions, compounding alone will grow it to your full FIRE number by retirement. The key insight this table makes visible: the younger you are, the smaller that number is — because your money has more years to compound. A 25-year-old might need only a fraction of what a 45-year-old needs to coast to the same retirement.
That’s why front-loading investing in your 20s and early 30s is so powerful. Hit your coast number early and you buy yourself optionality for decades: you can downshift to part-time work, switch careers, or simply stop stressing about retirement savings, while the portfolio quietly finishes the job. The table uses a real (after-inflation) return so the figures are in today’s dollars.
Frequently Asked Questions
What is my Coast FIRE number at 30?+
It depends on your expenses, retirement age, and return. At $40k expenses, a 65 retirement, and 7% real return, it is roughly $130k — use the table above for your exact figures.
Why is the Coast FIRE number lower when you are younger?+
Because there are more years for compounding to work. The same future target discounted over more years gives a smaller present amount.
Is Coast FIRE the same as being able to retire?+
No. Coast FIRE means you can stop saving for retirement; you still need income to cover current living expenses until your target retirement age.
Key Considerations
- Returns aren’t guaranteed. The table assumes a steady real return. A weak first decade can leave you short of target even if the long-run average holds — build in a margin by assuming 5–6% rather than 7%.
- The money must stay invested. Coasting only works if you don’t touch the principal before retirement. Any withdrawal pushes your coast number back up.
- Lower fixed costs help most. A smaller expense base shrinks both your FIRE number and every coast figure in the table — housing is usually the biggest lever.
Related Tools
Decision guide
Why the Coast FIRE number changes sharply with age
Each additional year gives current savings another year to compound. The required Coast balance is lower at younger ages, but the answer is more sensitive to assumed real return and retirement spending.
If the target is in today's dollars, use an after-inflation return.
The gap between ages is the value of lost compounding time.
What this model includes
- Age-specific Coast targets
- Growth from each age to retirement
What to add outside the model
- Future savings after reaching Coast FIRE
- Market paths, taxes, and changes in retirement age
Calculation standard: Formula details, source policy, tests, and limitations are documented in the FinancialDepth methodology. Reviewed July 18, 2026.