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What is Coast FIRE?

How a single number tells you when your savings can grow on their own.

Coast FIRE is the point at which the money you've already invested could grow — without any new contributions — to the amount you'd need at retirement. Once you reach it, you still need to earn enough to cover today's expenses, but you no longer have to save for retirement.

The math in two steps

1. Find your FIRE number. Divide expected annual retirement spending by a withdrawal rate. At $60,000 a year and 4%, that's $1,500,000.

2. Discount it back to today. Divide the FIRE number by (1 + expected real return) raised to the number of years until retirement. With 30 years at 5%, $1,500,000 ÷ 1.05³⁰ ≈ $347,000.

Why it's useful

• It turns a far-off goal into a milestone you can actually hit.
• It shows how powerful early savings are.
• It can inform career choices, like going part-time.

Watch the assumptions

Small changes in return or withdrawal rate move the answer a lot. Markets don't deliver a steady average, which is why tools like stress tests and Monte Carlo simulation exist.