Coast FIRE Calculator
Find your Coast FIRE number -- what you'd need saved today to reach your retirement target on growth alone, with zero further contributions.
Used with the 4% rule to set your target.
Your Coast FIRE number
$184,809
Needed today to coast to your target
Retirement target (4% rule)
$1,500,000
Still needed to coast
$34,809
At a 7% return over 30 years, your current savings alone are projected to reach $1,217,474.62 -- short of the $1,500,000.00 target, so you'd still need either more savings today or continued contributions.
How it's calculated
First, the same 4%-rule target every retirement page on this site uses:
target = annual spending ÷ 4% (25x spending, at the default rate)
Then the coast number is simply that target, discounted backward by the same monthly-compounded growth your money would experience getting there -- the site's one production growth engine run in reverse:
coast number = target ÷ (1 + r/12)12 × years to retirement
If your current savings already meet or exceed that number, growth alone is projected to carry you the rest of the way with no further contributions required.
Worked example
The calculator's own defaults: $150,000 saved today at age 35, retiring at 65 (30 years), spending $60,000/yr in retirement, at a 7% expected return.
| Retirement target (25x spending) | $1,500,000.00 |
| Coast number (needed today) | $184,808.78 |
| Projected balance at 65 (no more contributions) | $1,217,474.62 |
| Still needed to coast | $34,808.78 |
At $150,000, this example is $34,808.78 short of its $184,808.78 coast number -- not there yet, but the gap is the number to watch as savings grow. Plug the same inputs into the calculator above and it lands on the same figures to the penny.
Frequently Asked Questions
What does "Coast FIRE" actually mean?
It's a personal-finance community term, not an official or regulated one: the point at which your current savings, left completely alone with zero further contributions, are projected to grow into your full retirement number by the time you retire. Once you're past your coast number, any additional saving is optional rather than required -- though most people who reach it keep contributing anyway, just with less pressure.
How is my retirement target (the "FIRE number") calculated?
This calculator uses the same 4% rule as the site's "on track" retirement calculator: target = annual spending at retirement ÷ 4% (i.e. 25x your spending). That comes from William Bengen, 1994, Journal of Financial Planning -- a rule of thumb based on historical U.S. market data, not a guarantee, and you can enter your own spending figure to match your real plan rather than a generic estimate.
Does this calculator assume I stop saving entirely?
For the coast number itself, yes -- that's the definition of Coast FIRE: what you'd need TODAY assuming zero future contributions. It doesn't mean you have to actually stop; most people treat crossing this number as a flexibility milestone (room to cut hours, change careers, or simply save less aggressively), not a hard stop signal.
Why does a small change in expected return move my coast number so much?
Because the coast number divides your target by a growth factor raised to the power of your years to retirement -- compounding math means the exponent, not the rate itself, does most of the work over a multi-decade horizon. A return assumption that's off by even 1-2 percentage points can move the required coast number substantially; try a couple of different rates in the calculator above to see the real range rather than trusting a single number.
Is Coast FIRE the same as regular FIRE?
No -- "FIRE" (Financial Independence, Retire Early) generally means having your full number saved so you could stop working and live off withdrawals now. Coast FIRE is a weaker, earlier milestone: your money will GET you there by a stated future age on growth alone, but you're not there yet and likely still need income (from work or otherwise) to cover current expenses until then.
Figures on this page are estimates from the inputs you enter, not financial advice, and this site is not affiliated with any employer, plan administrator, bank or the IRS. Real accounts vary by plan rules, taxes and fees this tool doesn't model -- see the Terms.