Coast FIRE Calculator
Find your Coast FIRE number — the amount invested today that grows into your full retirement target with no more contributions — and when you reach it.
Coast FIRE is the point where the money you already have invested will grow, with no further contributions, into a full retirement nest egg by your chosen retirement age. From then on you only have to earn enough to cover today's bills. This calculator finds your Coast FIRE number and, if you are not there yet, the age you reach it if you keep investing.
How to use this tool
- Enter your age and the age you plan to retire.
- Enter your yearly spending in retirement, in today's dollars, and an assumed withdrawal rate.
- Enter what you have invested now and what you add each year.
- Set the expected return and inflation, then compare your balance with the Coast number age by age.
Formula
Coast FIRE number = (Spending ÷ Withdrawal rate) ÷ (1 + real return)^years
Spending ÷ withdrawal rate is your FIRE number — 25 × spending at 4%. Years is the time left until retirement. Real return = (1 + return) ÷ (1 + inflation) − 1, which keeps every amount in today's dollars.
Example
At 30, planning to retire at 65 on $40,000 a year with a 4% withdrawal rate, your FIRE number is $1,000,000. A 7% return with 3% inflation is a real return of 3.88%, so the Coast number today is 1,000,000 ÷ (1.07 ÷ 1.03)^35 ≈ $263,600. With $90,000 invested and $12,000 added each year, your balance catches up with the Coast target in about 21 years, at age 51; from then on you could stop contributing.
Frequently asked questions
What is the difference between Coast FIRE and FIRE?
FIRE means you have enough to stop working now. Coast FIRE means you have enough that growth alone will get you to FIRE by a set age, so you can stop saving for retirement but still need income for current expenses.
Is 4% the right withdrawal rate?
The 4% figure comes from historical U.S. stock and bond research, including William Bengen's 1994 study of retirement withdrawals. A longer retirement calls for testing lower rates, which raise the FIRE and Coast numbers. Historical results do not guarantee future withdrawals.
Why does the calculator use a real return?
Your spending will rise with prices. Taking inflation out of the return keeps the Coast number in today's dollars, so you can compare it with your current balance directly.
What if markets do badly after I stop saving?
Coasting depends entirely on growth, so a poor decade pushes your retirement date back. Many people keep a buffer above the Coast number or keep contributing a small amount.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026-10-30