Coast FIRE calculator: when can you stop saving, and is the money reachable?
Coast FIRE is the point where the money already invested will grow to your full FIRE number on its own, so new savings can stop and your pay only has to cover today.
Coast FIRE number today
$318,867
$198,867 to go. At your saving pace you can coast from age 55.
| FIRE number at retirement | $1,250,000 |
| Needed today to coast | $318,867 |
| Age you can stop saving | 55 |
| Retiring after 59½ | no 10 % |
Worked out by Radif Partners · How we calculate · figures read on irs.gov and healthcare.gov · not personal financial advice
Coast FIRE means you have invested enough that, without adding a dollar, the balance grows to your FIRE number by the age you plan to retire. At a 5 % return after inflation, someone aged 32 who wants $50,000 a year at a 4 % withdrawal rate needs $1,250,000 at retirement, and $318,867 invested today is enough to get there by 60. Aim for 50 instead and the coast number jumps to $519,401, because the money has ten fewer years to compound. The age matters for a second reason most Coast FIRE calculators skip: a 401(k) or IRA tapped before 59½ owes a 10 % additional tax unless an exception applies. Retiring at 50 means about 9.5 years paid from money you can reach, and that bridge costs $389,276 in today's dollars at $50,000 a year. The calculator above shows your coast number and the age at which your saving pace gets you there.
How the coast number is computed
The arithmetic is short. Take the FIRE number at retirement, here $1,250,000 for $50,000 of yearly spending at 4 %, and discount it back to today at the return you assume after inflation. With 28 years to go at 5 %, each dollar invested now becomes roughly four, so the coast number is about a quarter of the target: $318,867. Everything is in today's dollars, which is why the return is a real return and not a market headline.
The calculator then runs your saving forward year by year. With $120,000 invested and $15,000 added each year, the balance catches the shrinking coast number at age 55. Raise the yearly saving to $40,000 and the same person coasts from 38. That is the practical question behind the search: how many more years of heavy saving before the pressure comes off.
Already 40: how far is the coast line?
Coast FIRE number today
$393,127
| FIRE number at retirement | $1,150,000 |
| Needed today to coast | $393,127 |
| Age you can stop saving | 50 |
| Retiring after 59½ | no 10 % |
Coast numbers by age
The younger you are, the more of the work compounding does. The table keeps the same goal, $50,000 a year at 4 %, and compares two retirement ages for people who are 25 to 45 today.
| Age today | Coast number to retire at 60 | Coast number to retire at 50 | Gap |
|---|---|---|---|
| 25 | $226,613 | $369,128 | $142,516 |
| 30 | $289,222 | $471,112 | $181,890 |
| 35 | $369,128 | $601,271 | $232,143 |
| 40 | $471,112 | $767,392 | $296,280 |
| 45 | $601,271 | $979,408 | $378,136 |
A 25-year-old needs $226,613 to coast to 60, while a 45-year-old would need $601,271. Moving the finish line from 60 to 50 costs every row more than half again, which is the compounding of ten missing years. None of these figures say when the money can be spent, though.
Coasting to 50 leaves a gap before 59½
Here is the part that turns a simple ratio into a plan. Most coast balances sit in a 401(k), a 403(b) or an IRA, because that is where workplace saving goes. Those accounts reach the full FIRE number on schedule, but if the date on the calculator is earlier than 59½, a withdrawal on that date usually owes the 10 % additional tax on top of income tax. The coast math says the money is big enough; the tax code says part of it is still locked.
At $50,000 a year, the stretch from 50 to 59½ costs $389,276 in today's money (nine and a half years of withdrawals, discounted at 5 %). That sum has to come from accounts you can reach: a taxable brokerage account, Roth IRA contributions (which come out tax-free and penalty-free at any age), a governmental 457(b), or pre-tax money released by an exception. Leave your job in or after the year you turn 55 and the rule of 55 opens that employer's 401(k); the remaining bridge from 55 shrinks to $206,730. Before 55 the usual tools are a 72(t) series of equal payments or a Roth conversion ladder started five years ahead.
So a Coast FIRE target with an early date is really two targets. One is the coast balance, which can sit anywhere. The other is a bridge fund in reachable accounts, which has to exist by the retirement date, not later. In the faster example above, the saver who puts away $40,000 a year coasts to 50 from age 47; if every dollar of that went into a 401(k), the coast is real but the first decade of retirement is not funded.
Pick an early date and see the warning row
Coast FIRE number today
$560,953
| FIRE number at retirement | $1,350,000 |
| Needed today to coast | $560,953 |
| Age you can stop saving | not before retiring |
| Retiring before 59½: plan the access | see the bridge |
A worked case: coasting to 55
Take a 38-year-old with $300,000 invested who saves $25,000 a year and wants $48,000 a year from 55. The FIRE number is $1,200,000, the coast number today is $523,556, and at that saving pace the balance crosses the coast line at age 51. From then on, contributions can stop and the money is expected to reach the target by 55 on its own.
Fifty-five is a useful date in this plan. Someone who leaves the employer in or after the calendar year of their 55th birthday can take money from that employer's 401(k) with no additional tax, so a balance built in the current plan does not need a separate bridge for those years. What it does not cover is an IRA or an old 401(k) from an earlier job, which stay locked until 59½. Moving an old plan into the current one before leaving, when the plan accepts rollovers in, brings that money under the same rule. Retire one year earlier, at 54 in a year when you do not turn 55, and the exception is lost for the whole stretch.
What coasting does not cover
Coasting means your paycheck still pays every bill until the retirement date, and it means the invested money is never touched. A layoff that forces withdrawals at 45 breaks the arithmetic. The figure also assumes a steady real return; real markets deliver the same average in very different orders, and a bad decade just before the date leaves you short. The calculator does not include tax on withdrawals or health premiums before Medicare, which the FIRE number calculator adds to the target itself.
Two habits make a coast plan sturdier. Keep a margin above the coast number rather than stopping the day you cross it, and decide early which account will pay the first years. The bridge page walks through the order in which each account opens before 59½.