How to Calculate Your Coast FIRE Number (and Real People Whose Money Kept Growing)

Coast FIRE means you've invested enough that, even with no more large contributions, compound growth should carry your portfolio to a full retirement number by the time you need it. You keep working to cover today's bills; the retirement account takes care of itself. Calculating it takes two steps.

Step 1: Your full FIRE number

Grant Sabatier, who reached financial independence at 30, told CNBC Make It the standard shortcut: multiply your expected annual spending by 25. Spending $40,000 a year means a $1 million target. That comes from the 4% rule; more cautious research suggests withdrawal rates closer to 3.3%, which would push the same $40,000 of spending to about $1.2 million.

Step 2: Work backward to today

Your Coast FIRE number is the amount that grows into that target on its own. Divide the full number by the growth you expect over the years left — for example, at a 7% real return, money roughly doubles every 10 years, so $1 million needed in 30 years means about $130,000 invested today. Whatever you assume, the real-world stories below show the engine you're relying on: time.

Real investors who let compounding do the work

The earlier money goes in, the smaller your Coast FIRE number gets — which is why the stories with the biggest results started in their twenties. Every story links to its original source.