Coast Fire Calculator
coast fire calculator. Get instant, accurate results. Enter values for instant results with step-by-step formulas.
Reviewed by Sahil, Senior Finance & Tax Editor
Formula
Coast FIRE Number = Annual Expenses x 25 / (1 + real return)^years | Real Return = Nominal - Inflation
Coast FIRE is when your current savings, growing at the expected return rate, will reach your FIRE number by retirement without additional contributions. FIRE number = 25x annual expenses (4% rule).
Worked Examples
Example 1: $150K at age 30
Problem:$150K savings, age 30, retire at 65, $50K/yr expenses, 7% return
Solution:FIRE number: $1.25M. Coast number: $1.25M/(1.07)^35 = $116,720. $150K > $116,720
Result:Already Coast FIRE! Savings will grow to $1.6M+
Frequently Asked Questions
What is Coast FIRE and how is it different from regular FIRE?
Coast FIRE is the point at which your current invested balance, left completely untouched with no further contributions, will grow through compounding alone to a full traditional-retirement-age nest egg. Unlike full FIRE, Coast FIRE does not mean you stop working entirely — it means you can stop saving for retirement specifically and cover only your current living expenses with active income, since your existing investments are already 'coasting' to the finish line on their own.
Does Coast FIRE mean I can stop working entirely?
No — Coast FIRE specifically means you can stop contributing to retirement accounts, not that you can stop earning income altogether. You still need active income (from a job, freelance work, or a lower-stress career switch) to cover current living expenses like housing, food, and healthcare, since the invested balance is earmarked to grow untouched until your target retirement date.
What rate of return assumption should I use for a Coast FIRE projection?
Most Coast FIRE projections use a long-run average real (after-inflation) equity return assumption, commonly in the 5-7% range, reflecting a diversified stock-heavy portfolio held over one or more decades. Using a lower, more conservative assumption produces a higher required Coast FIRE number and a more cautious plan; using an aggressive assumption produces a lower number but more risk if actual returns fall short.
How does reaching Coast FIRE early in your 20s or 30s change the required balance compared to reaching it at 40?
Because compound growth depends on time as an exponent, reaching Coast FIRE a decade earlier can cut the required balance dramatically — the same target retirement nest egg might require roughly half the invested balance at age 30 with 35 years to grow compared to age 40 with 25 years to grow, at the same assumed rate of return. This is why aggressive saving in your 20s and early 30s has an outsized effect on Coast FIRE timelines.
Reviewed by Sahil, Senior Finance & Tax Editor · Editorial policy