Coast FIRE Calculator
Your Coast FIRE number is the amount that grows into your full FIRE number by retirement age with nothing more added: FIRE number ÷ (1 + real return) to the power of the years left. For $50,000 a year at 4%, retiring at 60 from age 32 at 5% real, that is $318,867. Once you hold it, you can stop saving.
Your Coast FIRE number
$318,867
Your Coast FIRE number at age 32
- FIRE number at 60 $1,250,000
- Years for it to grow 28
- Invested now $150,000 (below the coast number)
- Grows to by 60, nothing added $588,019
- Coast number if you retire 5 years later $249,841
| Age | Coast number | Grows to by 60 |
|---|---|---|
| 32 | $318,867 | $1,250,000 |
| 37 | $406,964 | $1,250,000 |
| 42 | $519,401 | $1,250,000 |
| 47 | $662,902 | $1,250,000 |
| 52 | $846,049 | $1,250,000 |
How is the Coast FIRE number worked out?
Coast FIRE number = FIRE number ÷ (1 + real return)^(retirement age − age now). You have reached it when your invested balance is at or above it.
Worked example. $50,000 a year at 4% needs $1,250,000 at 60. From age 32 there are 28 years to grow at 5% real: 1.05²⁸ = 3.920, so $1,250,000 ÷ 3.920 = $318,867. With $150,000 invested today you are $168,867 short; saving $24,000 a year closes that in the number of years the result shows (nine at these figures).
Why the coast number rises every year you wait
Each year that passes is a year of growth you no longer get, so the amount you must already hold goes up. At 5% real it rises about 5% a year: the number at 37 is about 28% higher than at 32. That is why the table in the results shows the coast number at later ages; it tells you how fast the target runs away if you pause.
What Coast FIRE does and does not buy you
It buys freedom from saving, not from working. Reaching it at 35 means a 25-year career can be anything that covers the bills: a lower-paid job you like, part-time, a business with no pressure to pay well. It does not protect you from a poor run of returns, a long gap in employment or a rise in planned spending; each of those moves the number back above you.
Pairing Coast FIRE with a cushion
Many people treat the coast number as a floor and keep saving a little past it, which turns a 60 retirement into a 55 one or covers a bad decade. The early retirement calculator shows what any extra saving does to the age, and the FIRE calculator gives the full year-by-year path.
Questions about Coast FIRE
What is Coast FIRE?
The point where what you have already invested will grow, on its own, into your full FIRE number by the age you want to retire. From then on you only need to earn enough to cover today’s spending; you can stop saving for retirement and “coast”.
How is the Coast FIRE number calculated?
FIRE number ÷ (1 + real return) raised to the years left. For $1,250,000 needed at 60, from age 32 at 5% real: $1,250,000 ÷ 1.05²⁸ = $318,867.
What if I am not there yet?
The calculator keeps adding your yearly saving and tells you the year you cross the coast line, which moves up each year because there are fewer years left to grow. The table shows the coast number at ages 5, 10, 15 and 20 years from now.
Is Coast FIRE safe?
It depends entirely on the return holding for decades. At 3% real instead of 5%, the coast number for the example above rises by about 71%, from the figure shown to about $546,000. Test it at a low return, and remember you still need an income until the money is ready.
What is the difference from Barista FIRE?
Coast FIRE means you keep working for your spending but stop saving; your job can be anything that pays the bills. Barista FIRE means you start drawing on the portfolio now and work part-time to fill the gap. The guide compares them with one family’s numbers.