Coast FIRE Calculator

What Coast FIRE means

Coast FIRE is the point at which your invested balance, left completely alone, compounds to your retirement target by your retirement age. You are not financially independent and you still need income to cover current living costs, but you no longer need to save for retirement. Reaching it converts saving from an obligation into a choice, which is why people find it a more motivating milestone than a distant full-independence number.

The calculation

Divide the target retirement portfolio by (1 + real return) raised to the number of years remaining. The critical detail is using a real return, net of inflation, and stating the target in today's money. Mixing a nominal return with an inflation-adjusted target is the standard error and produces a Coast number far too low, which is the most consequential mistake you can make here.

Assumptions dominate the answer

Small changes in assumed return move the number enormously across a long horizon. A 7 percent real return versus 5 percent changes a 30-year projection by roughly 70 percent. Historical US equity real returns average around 6.5 to 7 percent, but that is one country's record over a favourable period, and sequence risk means your actual path will not be the average. Model 4, 5 and 6 percent and treat the spread as the honest answer.

Coasting is not the same as stopping work

You still need to cover living costs, so it means freedom to take lower-paid, more interesting or part-time work rather than freedom to stop. Health insurance, in systems where employment provides it, is frequently the binding constraint that makes coasting harder than the arithmetic suggests.

Why it is fragile

The plan depends on not touching the balance for decades. A career break, a health event, a house purchase or supporting family can force a withdrawal, and money removed early costs all its future compounding. Coasting works best with a separate emergency fund that keeps the invested balance genuinely untouchable.

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