Coast FIRE Calculator
The balance that grows into your retirement with no new money.
Your Coast FIRE number today
$81,290 to go$181,290
- Invested now
- $100,000
- FI number at 65
- $1,000,000
- Coast age
- 40
$40,000/yr ÷ 4%
in 10.4 yrs
You're $81,290 short of coasting today. Investing $10,000 a year gets you there in 10 years, 5 months (age 40); after that, compounding alone carries you to $1,000,000 by 65.
Try a what-if
Your numbers
$100,000
In today's dollars.
$40,000 / year
$10,000 / year
5.00% a year, real
4.00% → FI = 25.0× spending
Coast number = FI number ÷ (1 + real return)years to retirement. All in today's dollars; taxes and Social Security aren't modelled.
Want to retire early rather than coast? Find your date with the FIRE calculator. The fastest way to build the coast balance is usually your 401(k) match and a Roth IRA.
Next steps
If you're 30, plan to retire at 65 on $40,000 a year, and expect a 5% real return, your Coast FIRE number is about $181,290 — invest that much today and compound growth alone reaches your $1 million FI number by 65. With $100,000 invested and $10,000 a year going in, you'd hit it in about 10.4 years, around age 40. This Coast FIRE calculator finds your coast number, shows whether you've already passed it, and — if not — the age you can stop contributing if you keep investing until then. The chart shows the coast line rising toward your FI number, your portfolio meeting it, and what happens if you stop investing today.
How this calculator works
- Enter your age and the age you want to retire.
- Enter what you have invested for retirement today.
- Enter your expected annual spending in retirement, in today's dollars.
- Enter how much you'll keep investing each year until you reach Coast FI.
- Set a real return and withdrawal rate, then read your coast number, how close you are, and the age you can start coasting.
FI number = spending ÷ withdrawal rate
coast number = FI number ÷ (1 + r)^(years to retirement)
coast date: first month where balance ≥ FI number ÷ (1 + r)^(years left)The coast number is the present value of your FI number at the retirement age. Each month you keep contributing, the remaining years shrink and the required coast balance rises toward the FI number; the coast date is when your growing portfolio first catches that rising line. After that, growth alone gets you to FI.
- r
- Real (after-inflation) annual return
- years to retirement
- Retirement age − current age
- spending
- Annual retirement spending in today's dollars
Frequently asked questions
What is Coast FIRE?
Coast FIRE means you've invested enough that, with no further contributions, compound growth alone will reach your full retirement number by your target age. From then on your job only has to cover current living costs, so you can downshift to lower-paid or part-time work while the portfolio coasts to financial independence.
How do I calculate my Coast FIRE number?
Divide your FI number by (1 + real return) raised to the years until retirement. Spending $40,000 a year at a 4% withdrawal rate gives a $1 million FI number. At age 30, retiring at 65 with a 5% real return, the coast number is $1,000,000 ÷ 1.05^35 — about $181,290.
How long until I can coast?
With $100,000 invested at 30 and $10,000 a year going in, a 5% real return reaches the coast line in about 10.4 years — around age 40 — for a $1 million goal at 65. Raising contributions to $15,000 a year shortens that to about 6.3 years. After that point, further contributions are optional.
How much does my age change the Coast FIRE number?
A lot, because time does the heavy lifting. For a $1 million FI number at 65 and a 5% real return, the coast number is about $142,046 at age 25, $181,290 at 30, $231,377 at 35 and $376,889 at 45. Every decade you wait, the amount you need grows by roughly 63%.
What if my investment returns are lower than expected?
Your coast number rises and your coast date moves out. For the same $1 million goal at 65, dropping from a 5% to a 4% real return lifts the coast number at age 30 from about $181,290 to $253,415. Use a cautious real return and recheck every year — contributing a little longer is a cheap hedge.
Sources used in this calculator
- NYU Stern (Damodaran) — S&P 500 Annual Returns 1928–2025S&P 500: 10% (as of 2026 (1928–2025 dataset)) — basis for the ~5% real-return default(opens in a new tab)
- Bureau of Labor Statistics — CPI-U (long-run avg)Long-run CPI Inflation: 3% (as of 2026) — subtracted to get a real return(opens in a new tab)
- Cooley, Hubbard & Walz (1998), "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable" (the Trinity study), AAII JournalThe 4% safe-withdrawal-rate default and the 25× FI number(opens in a new tab)
Reviewed by the Money Scale editorial team. How we source our data
Related calculators
See all- FIREYour FI number, years to financial independence, and age.
- 401(k) ProjectionProject a 401(k) with employer match and salary growth.
- Roth IRAProject tax-free Roth IRA growth across decades.
- Retirement BasicsSee if your savings rate gets you to 65.
- Compound InterestTextbook compound interest with monthly contributions.
Professional calculator
Retirement Planner
Coasting to a number is step one. The Retirement Planner shows how that balance turns into income, with taxes and Social Security.
Open the Retirement PlannerFree, no signup, runs in your browser. Educational modeling only — not financial advice.
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