What is a coast fire calculator?

A coast fire calculator is a financial planning tool that estimates how much you need to invest today so your money grows, untouched, into your full retirement goal by your target retirement age.

How to calculate my coast fire number?

Divide your target retirement portfolio (often 25x your annual expenses) by (1 + your expected annual return) raised to the power of the years remaining until retirement. This tells you the amount needed to be invested today.

Why does compound growth matter for Coast FIRE?

Compound growth is the entire mechanism behind Coast FIRE. Once you reach your number, your investments grow exponentially over time, allowing you to stop contributing while still reaching your retirement goal on schedule.

When should I start using a coast fire retirement calculator?

The earlier, the better. Starting in your 20s or early 30s gives your investments more time to compound, meaning you'll need a smaller invested amount today to reach the same future goal.

Which is better: Coast FIRE or full FIRE?

Neither is universally "better" - it depends on your goals. Full FIRE means retiring completely early, while Coast FIRE offers more flexibility, letting you reduce work stress or income while still reaching financial independence by traditional retirement age.

Should I include Social Security in my coast fire calculator inputs?

Most planners leave Social Security out of the core calculation to build in a safety margin, since future benefit amounts and eligibility rules aren't guaranteed. If you have a stable pension, it's reasonable to subtract expected pension income from your annual retirement expenses instead.

Is "coastFI" the same as "Coast FIRE"?

Yes. "CoastFI" and "Coast FIRE" refer to the same concept and are used interchangeably. Some prefer "coastFI" since the strategy involves continuing to work rather than retiring early in the traditional FIRE sense.

Coast FIRE Calculator

Find when compound growth alone can fund your retirement

Calculateur Coast FIRE

Find the number that makes saving for retirement optional - when compound growth alone will finish the job. Interactive chart, year-by-year table, today's-money math, and multi-share options for every scenario.

Calculateur Coast FIRE

Tous les résultats sont en valeur d'aujourd'hui — l'inflation est déjà prise en compte.

Your details

Current age

Retirement age

Invested so far

Monthly contribution

Annual spending in retirement

Advanced assumptions7% growth · 3% inflation · 4% withdrawal

Sensible defaults are pre-filled - only change these if you have a specific view. Every result stays in today's money.

Growth

Inflation

Withdrawal

Your Coast FIRE number today

$395,332

You're 30% of the way there- $275,332 to go.

Full FIRE number

$1,500,000

4% withdrawal rate

Coast age (if you keep contributing)

> 65

raise contributions or spending assumptions

At 65 if you stop saving today

$455,314

not enough yet on its own

At 65 if you keep contributing

$1,334,009

vs $2M needed

Not coasting yet - you're 30% of the way there

You'd need about $275,332 more invested today to coast. Or raise your monthly contribution, retire a little later, or trim retirement spending to close the gap.

Keep contributing Coast from todayCoast target

Assumes contributions and growth are steady, in today's money (real return ≈ 3.9%/yr). This is an educational estimate, not financial advice - markets are not steady, and taxes and retirement account rules affect real outcomes.