Coast FIRE is a savings milestone: hit it once, and your investments grow to fund retirement without another contribution. These three numbers are all we need to find yours.
This is your current invested balance: 401k, IRA, brokerage accounts, anything invested in the market.
Coast FIRE is one of the most liberating milestones in personal finance. Once you hit your number, you have effectively taken retirement off the table as a financial worry. Your invested money does the work from that point forward, compounding on its own until you are ready to stop working.
We start with your annual spending in retirement and project it forward for inflation to the year you plan to stop working. Using the 4% rule, we turn that future spending into the total nest egg you'll need. Then we work backwards: given your expected return and the years you have left, we solve for the single amount you'd need invested today for it to compound up to that nest egg on its own. That figure is your Coast FIRE number.
Most Coast FIRE calculators assume one fixed rate of return for your entire life, say 7% every year from age 30 to 65. Real portfolios don't work that way. As you approach retirement, the standard approach is to shift from stocks toward bonds and cash to protect against a market drop right before you need the money. That lowers your expected return in the final stretch.
A fixed rate calculator quietly overstates your ending balance because it assumes you'll keep earning stock like returns even at 64. A glide path tapers your expected return as retirement approaches, so the projection reflects how money is actually managed near the finish line. The result is a more honest, usually slightly higher, Coast FIRE number, which is the safer number to plan around.
Say you're 30, want to fully retire at 60, and expect to spend $50,000 a year in retirement. With a fixed 7% real return, you'd need about $164,000 invested today to coast. Switch on the glide path, which tapers returns over your final decade the way target-date funds do, and the honest number rises to about $199,000. That $35,000 difference is exactly the cushion a fixed rate tool hides from you. Try your own numbers above to see how sensitive your Coast FIRE number is to each input.
Benchmarks using the calculator's defaults: retirement at 65, a 7% real return (10% nominal, 3% inflation), the 4% rule, and the glide path on. Each cell is what you'd need invested today to stop contributing entirely:
| Your age | $40k/yr spending | $50k/yr spending | $60k/yr spending |
|---|---|---|---|
| 25 | $81,000 | $101,000 | $121,000 |
| 30 | $113,000 | $142,000 | $170,000 |
| 35 | $159,000 | $199,000 | $239,000 |
| 40 | $223,000 | $279,000 | $335,000 |
| 45 | $313,000 | $391,000 | $470,000 |
| 50 | $439,000 | $549,000 | $659,000 |
The pattern to notice: every 5 years you wait roughly adds 40% to the number, because you lose the highest-compounding years. Hitting Coast FIRE at 25 takes about a quarter of what it takes at 45. For a deeper cut by your exact age, see Coast FIRE by age.