Coast FIRE Calculator
Find your Coast FIRE number, the amount you need invested now so that, without adding another dollar, it grows to your retirement goal by your target age.
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About the Coast FIRE Calculator
Coast FIRE means you have saved enough that compound growth alone will carry your investments to a full retirement fund by your target age, so you only need to earn enough to cover current expenses. This calculator uses the 4% rule to set your retirement number and then discounts it back to today using an inflation-adjusted return.
How to use it
- Enter your age, target retirement age and the yearly spending you expect in retirement in today's dollars.
- Set a withdrawal rate and a real (after-inflation) return, then enter what you have invested.
- Press Calculate Coast FIRE to see your goal, your Coast FIRE number and the gap.
Coast FIRE formula
Coast number = FI number ÷ (1 + real return)years to retirement. With a $1,250,000 goal, a 5% real return and 30 years, the Coast FIRE number is about $289,000.
Related FIRE terms
| Term | Meaning |
|---|---|
| FI number | Annual spending ÷ withdrawal rate (25 × spending at 4%) |
| Lean FIRE | Retiring on a small budget |
| Fat FIRE | Retiring on a generous budget |
| Barista FIRE | Part-time work covers the gap |
Frequently asked questions
What is Coast FIRE?
It is the point where your existing investments will grow to your retirement goal on their own, even if you stop saving.
How do I calculate my Coast FIRE number?
Multiply your yearly retirement spending by 25 (4% rule) and divide by (1 + real return) raised to the number of years until retirement.
What return should I use?
Use a real return after inflation, such as 4% to 6% for stock-heavy portfolios. Lower numbers make a more cautious plan.
Is the 4% rule safe?
It is a guideline based on historical data for a 30-year retirement. Longer retirements may need a lower withdrawal rate.
Does Coast FIRE include Social Security?
No. Social Security and pensions can lower the portfolio you need. Use the retirement calculator to include them.
Last reviewed: November 2026. Estimates only, not financial, tax or legal advice.