What Is Coast FIRE?
The point where your invested money can finish the job without another dollar of contributions.
On a $1.5M retirement target at 7%, you reach Coast FIRE at age 30 with about $140,494 invested. From there, compounding alone is expected to carry it to $1.5M by 65 — no more contributions needed. Start at 40 and the coast number jumps to about $276,374.
The coast number, in one formula
Coast FIRE is the amount you need today so that, left to compound at a reasonable return, your portfolio reaches your retirement target by the age you plan to retire. The math:
Coast number = target ÷ (1 + rate)(retire age − current age)
Here is what that looks like for a $1.5M target at age 65, assuming a 7% return:
| Current age | Coast number (7%) |
|---|---|
| 30 | $140,494 |
| 40 | $276,374 |
| 50 | $543,669 |
Notice the pattern: starting 10 years later roughly doubles the coast number. Time is the cheapest input. Run your own coast number →
Coast FIRE does not mean retiring today
Reaching your coast number means you no longer need to save for retirement — but it does not mean you stop working. Most people still earn to pay current living costs while the portfolio compounds. Coast FIRE is a milestone on the way to full FIRE, not the finish line. You can think of it as "retirement savings: done, paycheck: still needed for now."
Why the return assumption matters so much
The coast number is highly sensitive to the return you assume. Use a lower, more conservative return and the required amount rises sharply. This is why it is worth stress-testing the assumption rather than trusting a single number — and why inflation-adjusted retirement planning keeps the picture honest.
Risk & limitations
- 7% is a hypothetical long-run assumption — not a guarantee; returns vary.
- The model ignores inflation adjustments, taxes and fees.
- Reaching the coast number assumes you can leave the money invested until retirement age.
- Educational projection only, not personalized financial advice.
Sources: The 4% withdrawal rule originates from the Trinity Study (1998), a historical analysis of sustainable portfolio withdrawal rates. · Long-run return context: NYU Stern (Damodaran). Educational projection only.