Coast FIRE Calculator

Coast FIRE is the point at which you have enough invested that compound growth alone will reach your full financial independence number by your target retirement age, without any further contributions. Once you hit your coast number you can stop saving for retirement and only need to earn enough to cover your current living costs. This calculator finds that number, tells you whether you are already there, and projects the date you reach it at your current contribution rate.

It is your FI number discounted back to today at your real return. First we work out the FI number (annual retirement spending divided by your withdrawal rate, so 25 times spending at 4%). Then we divide it by (1 + real return) raised to the number of years until retirement, where real return is your expected return minus inflation. The result is the smaller amount that, left to compound untouched, grows into the full FI number by your retirement age.

Regular FIRE asks when you can stop working entirely, which needs your full FI number. Coast FIRE asks when you can stop contributing, which needs only the coast number, the present value that grows into full FIRE on its own. Coast is a much earlier and smaller milestone. After coasting you keep working to cover today's expenses, but your retirement savings are effectively done.

You are already coasting if your invested assets today are at or above your coast number. Enter your figures and the calculator gives a clear verdict plus how far above or below the line you are. If you are already coasting, growth alone should reach your FI number by retirement even if you never invest another dollar, though it is wise to keep a buffer for weak markets.

Your FIRE number is the portfolio size that lets investment returns cover your living costs indefinitely: annual spending divided by your safe withdrawal rate. At the classic 4% rule that is 25 times your yearly expenses, so 40,000 a year needs one million. This tool doubles as a FIRE number calculator: enter your spending and withdrawal rate and it shows the full number alongside the smaller coast number you need today.

Fat FIRE means retiring on a larger, no-compromises budget rather than a lean one, which raises your FI number and therefore your coast number. This calculator handles any target: enter a higher retirement spending figure (or type a bigger FI number directly) and it recomputes the coast number for that Fat FIRE lifestyle, so you can see how much you need invested today to coast into a comfortable retirement.

Your savings rate does not change the coast number, but it decides how fast you reach it. A higher monthly contribution pulls the coast date earlier; a lower one pushes it out or, if it is zero, means you only coast when your existing assets already clear the line. Used as a FIRE savings rate calculator, this tool lets you raise or lower the monthly amount and watch the coast age and years-to-coast move in response.

Mathematically yes: if your assets equal the coast number and markets deliver your assumed real return, growth alone reaches your FI number by retirement. In practice returns vary, so many people keep contributing a little, hold a cash buffer, or plan to resume saving if a bad market stretch leaves them behind. Treat the coast point as permission to ease off, not a guarantee to stop forever.

A common starting point for a diversified stock-heavy portfolio is a 7% nominal return with 2.5% inflation, which is about a 4.4% real return. The coast number is very sensitive to this: a lower assumed return raises it sharply. If you want a margin of safety, model a return one or two points below the long-run average and treat any outperformance as a bonus.

Include only assets that actually compound and will fund retirement: brokerage accounts, index funds, workplace and private pensions, and similar. Leave out the home you live in, since it produces no withdrawals, and cash you plan to spend soon. If a state or workplace pension will start paying at retirement, it lowers the spending your portfolio must cover, so your true coast number is a little smaller than a portfolio-only estimate.