Coast FIRE is the amount you need invested today so that, with growth alone and no further contributions, it reaches your full FIRE number by retirement age.

How is the Coast FIRE number calculated?

It takes your FIRE number (annual spend divided by your withdrawal rate) and discounts it back to today using your expected real return over the years to retirement.

What withdrawal rate should I use?

Many in the FIRE community use the 4% rule, which implies a FIRE number of 25× annual spend. A lower rate (e.g. 3.5%) is more conservative and raises both your FIRE and Coast FIRE numbers.

What is a real return and why use it?

A real return is your investment return after subtracting inflation. Using it means the Coast FIRE number is in today's money, so you don't have to separately adjust for inflation.

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Coast FIRE Calculator

Coast FIRE is the milestone where your invested portfolio is already large enough that, with investment growth alone and no further contributions, it will grow to your full retirement target by the time you stop working. This calculator finds that number, tells you whether you have reached it, and shows what your current portfolio would grow to — useful for anyone pursuing financial independence who wants to know when they can ease off saving.

How it works

The calculation has two steps:

FIRE number = annual spending ÷ withdrawal rate. At a 4% withdrawal rate this is 25× your annual spend.
Coast FIRE number = the FIRE number discounted back to today using your expected real (after-inflation) return over the years until retirement:

Coast FIRE = FIRE number ÷ (1 + real return)^(years to retirement)

If your current portfolio is at least the Coast FIRE number, you are “coasting” and can stop contributing. The tool also projects what your current balance would grow to by retirement.

Example

Age 30, retiring at 65 (35 years), spending $40,000/year, 4% withdrawal, 5% real return:

FIRE number = 40,000 ÷ 0.04 = $1,000,000 growth factor = 1.05^35 ≈ 5.516 Coast FIRE = 1,000,000 ÷ 5.516 ≈ $181,290

So having about $181,290 invested today is enough to coast to a $1,000,000 target by 65 without adding another penny. All calculations run in your browser.