Coast FIRE Calculator

Coast FIRE is the point where you have enough invested that compound growth alone will carry your portfolio to your full retirement number by your target retirement age, with no further contributions. Once you reach it, you only need to earn enough to cover your current living expenses. Retirement funds itself in the background while you coast.

Start with your full FIRE number: annual retirement spending divided by your safe withdrawal rate, which is 25 times spending at the classic 4% rate. Then discount it back to today at your real return (expected return minus inflation). The formula is FIRE number ÷ (1 + real return) ^ years until retirement. A 30-year-old who wants $40,000 a year at 65, with a 7% return and 3% inflation, has a $1 million FIRE number and a Coast FIRE number of about $264,000 today.

Full FIRE means your portfolio can pay for your life right now, so working becomes optional. Coast FIRE is an earlier, smaller milestone: your portfolio can't support you yet, but it no longer needs new contributions to reach your goal on schedule. You keep working to pay the bills, just not to fund retirement. Because the coast number is a fraction of the full number, many people reach Coast FIRE decades before full FIRE.

No. Coast FIRE only means you can stop saving for retirement, not stop earning. You still need income to cover today's expenses. What changes is flexibility: with retirement already funded on paper, you can take a lower-paying job you enjoy, go part time, start a business, or simply redirect what you were saving toward travel, a house, or your kids.

This calculator compounds your balance at a real return, which is your expected return minus inflation. The defaults of a 7% return and 3% inflation give roughly a 4% real return, a common planning assumption for a diversified stock-heavy portfolio held for decades. Coasting leans entirely on compound growth, so a small change in the return assumption moves the coast number a lot. Testing a more conservative return is worth the two seconds it takes.

The coast math assumes decades of average returns, and real markets do not deliver average years on schedule. A long stretch of weak returns can leave you short at your target age. Spending creep is the other quiet risk: your coast number was sized to a specific retirement budget, and a bigger lifestyle needs a bigger number. Many people treat Coast FIRE as a checkpoint rather than a stop sign, easing off saving instead of quitting entirely so they keep a margin of safety.

This calculator leaves Social Security out, which makes the target conservative. Any benefit you receive later reduces how much your portfolio actually has to cover. If you want to see how much heavy lifting Social Security might do, our Social Security calculator estimates your benefit at different claiming ages, and you can subtract that from your planned spending here.

Yes, and many people do. Contributions past the coast point either pull your retirement date earlier or build a cushion against below-average returns. Every extra dollar compounds the same way. Coast FIRE just tells you the point where those contributions became optional rather than required.