Coast FI is the balance that grows into full financial independence by your retirement age without another contribution. At $40,000 of spending and a 4% withdrawal rate you need $1,000,000 at 65; discounted back 35 years at 5% real growth, that is $181,290 today. Hold that amount and saving becomes optional: you still need income for today's costs, but the portfolio needs no more feeding. This coast fi calculator shows your own number, the gap to it, and the date you cross it.
Spending $40,000 a year at a 4% withdrawal rate needs $1,000,000 invested. The Coast FIRE number for age 30 is $181,290, so you still need $181,290.
Spending $40,000 a year at a 4% withdrawal rate needs $1,000,000 invested. Your Coast FIRE number for age 30 is $181,290, and your portfolio is already $0 past it.
Coast FI is shorthand for coasting to financial independence. The term grew out of the FIRE movement, which needed a name for the stage after saving stops and before retirement begins. Coasting means the portfolio does the work: you add nothing, and time plus compounding carries it to the target. Both spellings — coast fi and Coast FIRE — describe the same calculation. The difference is emphasis. Coast FIRE usually names the whole strategy and the lifestyle it buys; coast fi is often used for the number itself. This page uses both, because the arithmetic does not care which one you write.
Three inputs decide the answer, and they are not equally powerful. Years until retirement matters most, because compounding is exponential: five extra years can cut the required balance by a quarter. The real return matters next, since it is what the portfolio earns after inflation, and small differences grow large over decades. Annual spending sets the target you are growing towards, so it scales the answer directly. Your current balance does not change the number at all — it only decides whether you have arrived. Two 30-year-olds with the same spending share one target, even if one is coasting and one is not.
Coasting is usually a choice about work, not about retirement. Once the number is covered, the next dollar of income can buy time instead of portfolio: fewer hours, a less demanding role, a cheaper city, or work that pays less and matters more. The trade is real. You are accepting that the retirement date now depends on returns you cannot control, and that a bad decade would need an answer. Many people keep contributing at a lower rate anyway, which shortens the distance and adds a buffer. The calculator shows that too: raise the yearly contribution and the crossing point slides left.
Coast FI stands for coasting to financial independence. It is the point where your invested balance no longer needs contributions, because left alone it grows into your full FI number by retirement. The term is used alongside Coast FIRE, and both describe the same milestone.
Yes, the arithmetic is identical. Coast FIRE is the more common spelling and usually names the strategy as a whole, while coast fi is often used for the number itself. The calculation is annual spending divided by the withdrawal rate, discounted back to today at your real return.
Yes. Divide annual spending by the withdrawal rate to get the FI number, then divide again by (1 + real return) raised to the years until retirement. At $40,000 and 4% the FI number is $1,000,000; over 35 years at 5% the divisor is 5.516, which gives $181,290.
No, it means you can stop saving. Your living costs still need income until the portfolio is actually drawn on, and the plan assumes you leave the balance untouched until retirement. What changes is the kind of work you need, not whether you need any.
The number rises. At 4% real instead of 5%, the divisor after 35 years is 3.95 rather than 5.52, so the balance you need today is about $253,415 rather than $181,290. A conservative assumption costs a larger target now; an optimistic one costs options later.