Coast Clock Calculator: find the age you can stop saving

Coast FIRE means you've invested enough that, with no further contributions, growth alone should reach your full retirement number by your goal age. After that you only need to earn enough to cover today's spending.

Retirement number = annual spending ÷ withdrawal rate (25× spending at 4%). In the simple case, coast number = retirement number ÷ (1 + real return)^{years to retirement}, where real return = (1 + return) ÷ (1 + inflation) − 1. The coast number we show also includes the rest of your plan: if you spend more than you take home, it adds what you'll draw from savings before you retire; if you plan to downsize, it subtracts what the sale adds; and if your mortgage runs into retirement, your retirement number includes the payments still to come. So with any of those, it won't match the simple formula. All figures are in today's dollars.

If at your current pace you wouldn't reach your coast number before about age 80, or before your retirement age at all, we flag it in red. It's a nudge, not a verdict: the levers below show what moves the clock most.

You can't spend home equity or withdraw 4% of it a year while you still live in the house, and it doesn't compound like an invested portfolio. So we leave it out of your savings unless you plan to sell and free up cash. If you own your home outright (no mortgage, or already paid off), turn on "Plan to downsize" under Advanced assumptions and enter your home's value and the price of your next home ($0 if you'll rent): the difference is added to your investments at the age you sell, and not a day earlier (or today, if you're selling now). With a mortgage, we don't count your home's value as available equity. If your mortgage will be paid off before you retire, choose "I have a mortgage" and set the payoff age: the payment comes off the spending your portfolio has to cover.

Your monthly payment and the age it's paid off already capture the rate: the bank set the payment so the loan ends on that date. We only need to know how much leaves your budget each month and when it stops. A fixed-rate payment stays the same in dollars, so in today's dollars it shrinks a little every year with inflation. After payoff, we assume the payment's value at that point (in today's dollars) goes to savings until you retire, and it drops out of your retirement spending. If the mortgage runs past retirement, we add enough to your retirement number to cover the remaining, shrinking payments.

Not yet. Income and spending describe your cash flow today, and we use the difference to estimate how much you save each month. If you spend more than you take home, we draw that gap from your savings each month until you retire. If you lowered your spending to account for Social Security or a pension, it would also look like you save more today, so the benefit would be counted twice. For now we assume your investments cover all of your retirement spending, which is a cautious estimate if you expect other retirement income.

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