🔥 Coast FIRE Calculator
Coast FIRE is the moment your invested savings become self-propelling: from that point on, compound growth alone can carry them to your full retirement target, even if you never save another dollar. This calculator works backwards from the retirement you want to the amount you would need invested today.
Enter your age, retirement age, current invested savings, expected return and the yearly spending you are aiming for. You will see your full FIRE number, your Coast FIRE number and exactly how close you already are — plus what happens to today's savings if contributions stopped right now. Figures are estimates in future dollars, before taxes.
How to use this calculator
Enter your ages, what you have already invested, the return you expect and the spending you are targeting, and the calculator works out how much you need invested today to be able to stop saving for retirement.
- Enter your Current age and the Retirement age you are targeting.
- Type your Current invested savings — everything already invested for retirement.
- Set the Expected annual return you think your investments will average.
- Enter your expected Annual spending in retirement, keep the Safe withdrawal rate at 4% (or adjust it), then press Calculate.
Why the Gap Stays the Same Percentage
It feels like time alone should close the gap, but the maths says otherwise. If you stop contributing, your savings grow at your expected return — and your Coast FIRE number grows at exactly the same rate, because each passing year leaves one less year for growth to do the work. The percentage gap therefore stays frozen while the dollar gap gets bigger. The only levers that move the percentage are contributing more now, earning a higher return, planning to spend less, or retiring later.
Frequently asked questions
What is Coast FIRE?
Coast FIRE is the point where the money you have already invested is enough to grow, entirely on its own, into the full amount you need at retirement. Once you pass it, you could stop adding new savings and still arrive on target — from then on, your job only needs to cover today's living costs.
How is the Coast FIRE number calculated?
First, your full FIRE number is worked out by dividing your expected yearly spending in retirement by your safe withdrawal rate — at 4%, that is 25 times your spending. That target is then discounted back over the years until retirement at your expected return: Coast FIRE number = FIRE number ÷ (1 + return) raised to the years remaining.
What does the progress percentage mean?
It compares what you have invested today with your Coast FIRE number. At 100% you have reached Coast FIRE. Below 100%, the results show how much more you would need invested today, and how far short your current savings would land at retirement if you never added another dollar.
If I stop contributing, will the gap close over time?
No — and this surprises many people. Your savings and your Coast FIRE number both grow at the same assumed rate, so the percentage gap stays exactly the same while the dollar gap widens. Only new contributions, a higher return, lower spending or a later retirement age move the percentage.
What return should I assume?
A long-run assumption of 6–7% a year is common in FIRE planning; a more cautious plan uses 4–5%. Try the calculator at two or three different rates before deciding: the Coast FIRE number is very sensitive to this input, especially when retirement is still decades away.
How is this different from the retirement calculator?
They answer different questions. The retirement calculator projects your balance while you keep contributing every month; this one asks how far today's savings alone would carry you. Running both side by side shows how much of your plan still depends on future contributions.