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Coast FIRE Calculator

Coast FIRE is the portfolio size you need today such that, with no further contributions, compound growth alone reaches your full FIRE number by your target retirement age.

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Coast FIRE is the portfolio size you need today such that, with no further contributions, compound growth alone reaches your full FIRE number by your target retirement age. It is the moment you can stop investing new money — you still need to cover today's expenses, but the long-term retirement goal is funded.

Enter the annual expenses you expect in retirement (in today's dollars), your safe withdrawal rate (4% is the standard default), your current age, your target retirement age, and your expected real (inflation-adjusted) return. Optionally enter your current invested savings to see whether you have already coasted and how much you would have at retirement if you never contributed another dollar.

Examples

Age 30, retire at 65, $40k expenses, 7% real return

FIRE target = $1,000,000 (40,000 / 0.04). Years to retirement = 35. Growth factor = (1.07)^35 ≈ 10.68. Coast FIRE ≈ $93,640. Saving that much by 30 means you could stop contributing entirely and still hit $1M by 65.

Age 40, retire at 65, $60k expenses, 6% real return

FIRE target = $1,500,000. Years = 25. Growth factor = (1.06)^25 ≈ 4.29. Coast FIRE ≈ $349,650. Higher current age and lower return both raise the bar substantially — Coast FIRE is most achievable when you start young.

Frequently Asked Questions

How is Coast FIRE different from full FIRE?
Full FIRE is the portfolio size at which a safe withdrawal covers your annual expenses indefinitely — you can stop working entirely. Coast FIRE is a smaller intermediate milestone: you can stop *contributing* and let compounding do the rest, but you still need income to cover today's expenses (a "coast job" or any income source).
What discount rate / return should I use?
Use a real (inflation-adjusted) return. Historically, US equities have returned about 7% real (10% nominal minus ~3% inflation). Bond-heavy portfolios are lower (4-5% real). Mixing real and nominal numbers will overstate your progress.
What if I'm already past Coast FIRE?
You're free to redirect savings elsewhere — paying down a mortgage, taking a sabbatical, switching to a lower-paying but more meaningful job. The math says compounding alone will hit your retirement target; new contributions accelerate to full FIRE rather than being required for it.
Does this account for inflation?
Yes — by convention, you enter expenses in today's dollars and use a real return. The 4% rule already adjusts withdrawals for inflation each year, and the Coast FIRE math inherits that framing. Don't mix in nominal returns or inflated future expense projections.

References

  1. Bengen, W. P. (1994). "Determining Withdrawal Rates Using Historical Data." — Journal of Financial Planning
  2. r/financialindependence community wiki — Coast FIRE — https://www.reddit.com/r/financialindependence/wiki/
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Quick Tips

Double check your inputs. Ensure units match (e.g., inches vs cm).

Did you know?
Calculators are estimates. Consult professionals for critical decisions.

Coast FIRE is the portfolio size you need today such that, with no further contributions, compound growth alone reaches your full FIRE number by your target retirement age. It is the moment you can stop investing new money — you still need to cover today's expenses, but the long-term retirement goal is funded.

How to Use This Calculator

Enter the annual expenses you expect in retirement (in today's dollars), your safe withdrawal rate (4% is the standard default), your current age, your target retirement age, and your expected real (inflation-adjusted) return. Optionally enter your current invested savings to see whether you have already coasted and how much you would have at retirement if you never contributed another dollar.

Understanding the Formula

Coast FIRE = FIRE target / (1 + r)^t, where FIRE target = annual expenses / safe withdrawal rate, r = expected real annual return, and t = years until retirement (retirement age − current age). Uses real returns and today-dollar expenses to keep inflation out of the math.

Examples

Age 30, retire at 65, $40k expenses, 7% real return

FIRE target = $1,000,000 (40,000 / 0.04). Years to retirement = 35. Growth factor = (1.07)^35 ≈ 10.68. Coast FIRE ≈ $93,640. Saving that much by 30 means you could stop contributing entirely and still hit $1M by 65.

Age 40, retire at 65, $60k expenses, 6% real return

FIRE target = $1,500,000. Years = 25. Growth factor = (1.06)^25 ≈ 4.29. Coast FIRE ≈ $349,650. Higher current age and lower return both raise the bar substantially — Coast FIRE is most achievable when you start young.

Frequently Asked Questions

How is Coast FIRE different from full FIRE?

Full FIRE is the portfolio size at which a safe withdrawal covers your annual expenses indefinitely — you can stop working entirely. Coast FIRE is a smaller intermediate milestone: you can stop *contributing* and let compounding do the rest, but you still need income to cover today's expenses (a "coast job" or any income source).

What discount rate / return should I use?

Use a real (inflation-adjusted) return. Historically, US equities have returned about 7% real (10% nominal minus ~3% inflation). Bond-heavy portfolios are lower (4-5% real). Mixing real and nominal numbers will overstate your progress.

What if I'm already past Coast FIRE?

You're free to redirect savings elsewhere — paying down a mortgage, taking a sabbatical, switching to a lower-paying but more meaningful job. The math says compounding alone will hit your retirement target; new contributions accelerate to full FIRE rather than being required for it.

Does this account for inflation?

Yes — by convention, you enter expenses in today's dollars and use a real return. The 4% rule already adjusts withdrawals for inflation each year, and the Coast FIRE math inherits that framing. Don't mix in nominal returns or inflated future expense projections.

Assumptions & Limitations

  • Returns are constant year over year. Sequence-of-returns risk in early retirement is the largest threat to a 4% withdrawal plan; a single bad decade right after Coast FIRE can break the math.
  • Expenses stay flat in real (inflation-adjusted) terms. Use today-dollar expenses with a real return assumption (~7% historical equity average), not nominal returns with inflated future expenses.
  • No new contributions are assumed once Coast FIRE is reached. If you continue contributing, you will reach full FIRE faster than the projection.
  • Does not account for taxes on withdrawals, which reduce effective spending power. Build the tax bill into "annual expenses."
  • No part-time income, Social Security, pension, inheritance, or rental income is included. Reduce the expense input by any of those that you can count on.

References

  1. Bengen, W. P. (1994). "Determining Withdrawal Rates Using Historical Data." — Journal of Financial Planning
  2. r/financialindependence community wiki — Coast FIRE — https://www.reddit.com/r/financialindependence/wiki/