The Coast FIRE formula
FIRE number = Annual spending ÷ Withdrawal rate
Coast FIRE number = FIRE number ÷ (1 + r)n
Coast FIRE number = FIRE number ÷ (1 + r)n
Here r is the expected real (after-inflation) annual return and n is the number of years until retirement. If your current invested balance is at least the Coast FIRE number, you can stop contributing and still retire on schedule — assuming returns average out as expected.
Example: You are 30, plan to retire at 65, want to spend $40,000 a year and use a 4% withdrawal rate. Your FIRE number is $1,000,000. At a 5% real return, the Coast FIRE number today is $181,290. With $100,000 invested you are $81,290 short. Adding $500 a month, you reach Coast FIRE at about age 52 — because the target keeps growing with time, it takes longer than a simple gap ÷ savings estimate suggests.
How to use your Coast FIRE number
- Front-load savings. Money invested in your 20s has the longest time to compound, so aggressive early saving can buy you decades of flexibility.
- Be conservative. A 1-point lower return raises the Coast number a lot over 30+ years. Try 4% as well as 5%.
- Keep retirement accounts invested. Coasting only works if the money stays in growth assets and you do not withdraw it early.
- Revisit yearly. Market swings move you above or below the line; recheck and top up if needed.
See the full-retirement target with the FIRE number calculator, or check how fast money doubles with the rule of 72.
Frequently asked questions
What is Coast FIRE?
Coast FIRE (coast financial independence) is the point where your invested savings, left alone to compound, will reach your full FIRE number by your planned retirement age. After that you only need to earn enough to cover current living costs — you can stop saving for retirement.
How is the Coast FIRE number calculated?
First find your FIRE number: annual retirement spending ÷ safe withdrawal rate (25× spending at 4%). Then discount it back to today: Coast number = FIRE number ÷ (1 + real return)^years to retirement. With $40,000 of spending, 4%, 5% real return and 35 years to go, that is $1,000,000 ÷ 1.05^35 ≈ $181,290.
Should I use a real or nominal return?
Use a real return (after inflation), such as 7% nominal − 2% inflation = 5%. That keeps every number in today’s dollars, so your spending figure stays meaningful.
What is the difference between Coast FIRE and Barista FIRE?
In Coast FIRE your portfolio is not touched until retirement; you work only to pay current bills. Barista FIRE usually means you already draw part of your living costs from investments and cover the rest with part-time work.