How much must I have invested today to stop contributing?
Your Coast FIRE number is the balance that grows into your FIRE number by retirement with no more saving. See yours and the age you reach it.
Withdrawal rate
The 4% rule (Bengen 1994; Trinity study): 30-year US history.
YOUR COAST FIRE NUMBERNOT YET
$460k
To stop saving and still reach $1,500,000 by 65 you need $460,414 invested today. You have $420,000 (91%) and add $4,300 a month, so at these inputs you can stop saving at age 35, 1 year from now, if the balance then earns a steady 3.9% real return every year for the 30 years to 65.
FIRE number
$1.50M
Invested today
$420k
Stop saving at
Age 35
Balance at 65
$1.54M
UNDERSTAND YOUR RESULT
When does your balance cross the coast number?
Your balance (today’s dollars)Coast number by age ($1.50M at 65)
Your balance first clears the coast number at age 35: $490k against the $478k needed at that age. After that it needs no more saving and grows to about $1.54M by 65, against a $1.50M FIRE number.
What if you retire earlier or later?
Retire at 55$254k to go
$674k
Retire at 60$137k to go
$557k
Retire at 65Your choice · $40k to go
$460k
Retire at 70You have this
$381k
Retire at 75You have this
$315k
Invested today, you would need $674k to retire at 55, $557k to retire at 60, $460k to retire at 65, $381k to retire at 70 and $315k to retire at 75. Each extra year before retirement gives the balance another year to grow, so a later retirement age needs less. Your $420k covers 2 of them.
What moves the needle
Each row re-runs the calculation with one change. Click to apply.How it's computed
FORMULA
FIRE number = annual spending ÷ withdrawal rate
r = (1 + nominal return) ÷ (1 + inflation) − 1
Coast number = FIRE number ÷ (1 + r)^(years until retirement)
Coast point = the first age your balance ≥ the coast number for that age
- Returns are real: 7.0% before inflation less 3.0% inflation is a 3.88% real return, so every figure is in today’s dollars.
- $51,600 a year ($4,300 a month × 12) is added at the start of each year until the coast point, then stops.
- The coast test runs once a year, at whole ages, on the balance at the start of that year, before that year’s contribution is added.
- Spending is treated as after-tax spending; taxes on withdrawals are not modeled.
- Social Security and pensions are not counted. If one will already be paying by your retirement age, you can lower the spending figure by that amount. Social Security retirement benefits cannot start before 62, so for an earlier retirement age leave them out: the balance has to fund the years before they start.
- Returns are steady each year. Real markets are not, so read the coast number as a target, not a promise.
WORKED EXAMPLE · SAMPLE NUMBERS
$60,000 ÷ 4.0% = $1,500,000 FIRE number. Real return = 1.070 ÷ 1.030 − 1 = 3.88%. Coast number = $1,500,000 ÷ 1.038835^31 = $460,414. You have $420,000, which is 91% of it. Saving $51,600 a year, your balance first clears the coast number for its age at 35: $489,915 against $478,294. From there it grows to $1,536,445 by 65.
SOURCES
[1]The Theory of InterestIrving Fisher, Macmillan, 1930 (real versus nominal interest)
[2]Determining Withdrawal Rates Using Historical DataBengen, Journal of Financial Planning, 1994
[3]Retirement Savings: Choosing a Withdrawal Rate That Is SustainableCooley, Hubbard & Walz (Trinity study), 1998
[4]CPI-U, All Urban ConsumersU.S. Bureau of Labor Statistics[5]Old-age insurance benefits: entitlement at age 62 (Social Security Act §202(a), 42 U.S.C. §402(a))U.S. Code, Office of the Law Revision CounselHSBuilt by Hussain Sehorewala · checked against worked examples · Sep 29, 2026
Keep this number honest as your life changes.
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Questions about this result
Coast FIRE means you already have enough invested that, left to grow with no more contributions, it reaches your FIRE number by your retirement age. You can stop saving for retirement, but you still earn to pay your current bills.
Divide annual spending by your withdrawal rate to get the FIRE number, then divide that by (1 + real return) raised to the years until retirement. Example: $40,000 a year at 4% is a $1,000,000 FIRE number; with a 7% return and 3% inflation (a real return of about 3.88%) over 35 years, the coast number is about $263,555.
No. Coasting means the retirement savings are on autopilot, not that the paychecks can stop. Your income still has to cover today’s living costs. To leave full-time work earlier with part-time income covering some spending, use the Barista FIRE calculator.
The balance compounds untouched for decades, so the return assumption matters a lot here. This page starts at 7% before inflation and 3% inflation, a planning assumption and not a forecast. Lower the return slider to see how far the coast number rises.
When the real return is positive, a later retirement age gives the untouched balance more years to compound, so less has to be invested today. At the default 3.9% real return, each extra year lowers the coast number by about 3.7% (1 ÷ 1.0388).
Coast FIRE stops your contributions and lets the balance grow until a traditional retirement age. Barista FIRE goes further: you leave full-time work early and cover part of your spending with part-time income while the portfolio covers the rest.
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