Coast FIRE explained

Coast FIRE means you've saved enough that, with no further contributions, compound growth alone will take your portfolio to your full FI number by a traditional retirement age. From that point on, you only need to earn enough to cover current expenses; you can stop saving for retirement entirely.

The Coast FIRE formula

Your Coast FI number is your FI number discounted back to today:

Coast FI number = FI number ÷ (1 + real return)^{years until retirement}

Example: you're 30, spend $50,000 a year, and want to retire at 60. Your FI number is $1,250,000 (25 × $50,000). At a 5% real return over 30 years, every dollar grows about 4.3 times, so your Coast FI number is $1,250,000 ÷ 4.32 ≈ $289,000. Have that invested at 30 and you could, in theory, never save another dollar.

How age changes the number

The earlier you hit it, the smaller it is. For the same $1.25M target at age 60 and a 5% real return:

Why people aim for Coast FIRE

• Career freedom. Once retirement is handled, you can take a lower-paying job you enjoy, go part-time, start a business or take a sabbatical.
• A milestone on the way to full FIRE. It's a meaningful checkpoint that often arrives in your 30s.
• Less pressure. Knowing the long-term problem is solved changes how work feels.

The catches

• It relies on assumed returns. A 5% real return is close to the long-run history of a stock-heavy portfolio, but 30 years of below-average markets would leave you short. Many people keep contributing a little after reaching Coast FI as insurance.
• You still have to cover today's bills, and keep investing during the coast years only if you want to retire earlier than planned.
• Spending creep. If your lifestyle grows, your FI number grows, and your coast number with it.

Check whether you're there with the Coast FIRE calculator.