Coast FIRE Calculator
This Coast FIRE calculator shows whether your current retirement savings, left alone to compound with no further contributions, would grow into your full retirement number by the time you retire. Enter your numbers to see your Coast FIRE target and whether you've already reached it.
Your age today.
When you plan to fully retire and start drawing down.
Everything you've saved toward retirement so far.
A long-run average, after inflation or before — be consistent with how your target below is expressed.
What you need saved by retirement age — use the FIRE Number Calculator if you're not sure.
Coast FIRE number (today)
$117,079
How much you'd need saved right now for compounding alone to reach your target by retirement age.
Positive means you've already hit Coast FIRE; negative shows how much more you'd need to get there.
How to use this coast fire calculator
- 1Current age, target retirement age and current savings: the basics of your timeline.
- 2Expected annual return: a long-run average — 6-8% is a common assumption for a diversified stock-heavy portfolio, lower if you want a more conservative estimate.
- 3Target retirement savings: your full FIRE number — use the FIRE Number Calculator (expenses ÷ safe withdrawal rate) if you haven't worked this out yet.
Understanding your results
Coast FIRE number is how much you'd need saved today for pure compounding — no more contributions — to reach your target by retirement age. Surplus (or gap) compares that to what you actually have: a positive number means you've already 'coasted' past the point where you need to keep contributing to reach your goal (though many people keep saving anyway, for an earlier or more comfortable retirement).
The formula
Coast FIRE number = Target ÷ (1 + Return)^(Years to retirement)This is simply the future-value compound interest formula solved backward: instead of asking 'what will my savings grow to,' it asks 'how much would I need today to reach my target, given only investment growth and no further contributions.' The more years you have until retirement, the smaller the number needed today, since compounding has longer to work.
A worked example
A 30-year-old targeting a $1,250,000 retirement number at age 65, assuming a 7% annual return, has 35 years for compounding to work. The Coast FIRE number today is roughly $117,100 — meaning $80,000 in current savings still has a gap of about $37,100 to close before contributions could stop entirely and compounding alone would finish the job.
Notes for the UK, US and India
Coast FIRE is popular because it reframes the goal: instead of 'save until retirement,' it's 'save until compounding takes over,' after which you could theoretically stop contributing (or work a lower-stress, lower-paying job) and still reach your number. Reaching Coast FIRE doesn't mean stopping work entirely — most people who hit it keep contributing for an earlier retirement or a bigger cushion.
Frequently asked questions
What's the difference between Coast FIRE and regular FIRE?+
Regular FIRE means you've saved enough to retire and live off withdrawals immediately. Coast FIRE means you've saved enough that, left to compound alone with no more contributions, you'd reach your full retirement number by a normal retirement age — you'd still need income to cover living expenses until then.
Should I use a real (inflation-adjusted) or nominal return rate?+
Be consistent — if your target retirement savings figure is in today's dollars, use a real (inflation-adjusted) return, commonly 4-6%. If your target is in future, inflated dollars, use a nominal return, commonly 7-10%.
Does hitting Coast FIRE mean I should stop contributing?+
Not necessarily — it's a milestone, not a mandate. Many people keep contributing after reaching Coast FIRE to retire earlier than their original target age, or to build a larger cushion than their minimum number.