Coast FIRE Calculator
Enter your age, planned retirement age, spending, and what you've already invested. You'll get your Coast FIRE number, how close you are, and the age at which compounding could take over entirely.
When the portfolio needs to be ready
In today's dollars
Brokerage, 401(k), IRA, other investments
Used to estimate the age you could coast
After inflation. 5% is a common long-run assumption
4% is the classic rule; 3-3.5% is more conservative
Coast FIRE number (today)
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Enter your age and spending
Your progress
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Age you could coast
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The cheapest retirement you'll ever buy
Compounding does most of its work in the later decades, which means dollars invested early are worth several of the dollars invested late. Coast FIRE exploits that: front-load the investing while you're young, then let time finish the job. The full concept, including who it suits and where it goes wrong, is in our Coast FIRE explainer.
What changes the number most
Three levers dominate: retirement spending (each $1,000 of annual spending adds $25,000 to the target at a 4% withdrawal rate), years of runway (coasting at 30 needs roughly half the balance of coasting at 44 for the same goal), and the return assumption. Try moving the return between 4% and 6% and watch the coast number swing; that sensitivity is why conservative inputs are worth using. The compound interest calculator shows the same growth curve on its own.
After you hit coast
Past the threshold, retirement saving becomes optional, not automatic. Many people keep contributing anyway (buffer against bad markets), downshift to more meaningful work, or redirect the freed cash toward nearer goals. Whichever you pick, the decision only stays sound if the balance is actually tracked against the plan, which is exactly what Stoia is for. And if full independence is the real goal, the FIRE calculator maps the rest of the road.
Frequently asked questions
What is Coast FIRE?
The point where your invested balance, left completely alone, will compound into a full retirement portfolio by traditional retirement age. Once you're past it, you only need work to cover current living costs; retirement is already funded.
How is the Coast FIRE number calculated?
Take your retirement number (annual spending divided by the withdrawal rate) and discount it backward by your expected growth rate for the years until retirement. Someone needing $1.25M at 65 with 5% real returns needs about $217,000 invested at 30 to coast.
What's the difference between Coast FIRE and regular FIRE?
Full FIRE means investments cover your living costs today, so work is optional now. Coast FIRE only means future retirement is handled; you still need income for current expenses. That makes the coast number dramatically smaller and reachable decades earlier.
Why does the calculator use after-inflation returns?
Your retirement spending is entered in today's dollars, so growth has to be measured the same way. Stocks have averaged roughly 9-10% per year before inflation over the long run; 5-7% is the common after-inflation planning range.
Does this account for Social Security?
No, and that makes it conservative. Any Social Security income would reduce the spending your portfolio must cover, lowering both your retirement number and your coast number.
Does this calculator save my numbers?
No. Everything runs in your browser and disappears when you leave. Nothing is uploaded or stored.
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