How much do I need if part-time income covers some spending?
Your Barista FIRE number pays the gap that part-time income leaves until it stops, and still grows to the full FIRE number by then. See it and your date.
Withdrawal rate
The 4% rule (Bengen 1994; Trinity study): 30-year US history.
YOUR BARISTA FIRE NUMBER
$1.15M
To fund the $36,000 a year that $24,000 of part-time income leaves until age 60, and still hold the full $1,500,000 FIRE number then, you need $1,150,088 invested today. You have $420,000 (36%) and add $4,300 a month, so at these inputs you can go part-time at age 44, about 10.1 years from now, when $1,246,907 is needed, if the balance earns a steady 3.9% real return every year until 60. Full FIRE would take 12.5 years, 2.4 years longer.
Full FIRE number
$1.50M
Go part-time at
Age 44
Needed then
$1.25M
Part-time years
15.9
UNDERSTAND YOUR RESULT
Terms:Barista FIRE
When can you go part-time?
Your plan: saving, then paying the gap (today’s dollars)Needed to go part-time at that age
Your balance reaches what going part-time needs at about age 44, 10.1 years from now: $1,250,093 against $1,246,907 needed. From then you stop saving and pay the $36,000 a year that $24,000 of part-time income leaves, and, if the balance earns a steady 3.9% real return every year, it is back at the full $1.50M FIRE number by age 60, when that income stops.
What if the part-time work lasts longer or shorter?
Years until you can leave full-time work
Part-time until 50needs $1.25M today
11.8 yrs
Part-time until 55needs $1.19M today
10.8 yrs
Part-time until 60Your choice · needs $1.15M today
10.1 yrs
Part-time until 65needs $1.11M today
9.5 yrs
Part-time until 70needs $1.08M today
9.0 yrs
The wait until you can leave full-time work is 11.8 years if it lasts until 50, 10.8 years if it lasts until 55, 10.1 years if it lasts until 60, 9.5 years if it lasts until 65, 9.0 years if it lasts until 70. The longer the part-time income lasts, the less the balance has to hold today, because it covers the gap for longer and the portfolio has more time to grow back to the full number.
How the number falls as part-time income rises
Balance needed to go part-time today
No part-time incomeThe full FIRE number
$1.50M
$15,000 a yearCovers 25% of spending
$1.30M
$24,000 a yearYours · covers 40% of spending
$1.15M
$30,000 a yearCovers 50% of spending
$1.05M
$45,000 a yearCovers 75% of spending
$804k
Another $10,000 a year of part-time income takes about $165k off the number while it lasts until age 60. Your $24,000 brings $1.50M down to $1.15M.
What moves the needle
Each row re-runs the calculation with one change. Click to apply.How it's computed
FORMULA
Full FIRE number = annual spending ÷ withdrawal rate; Gap = annual spending − part-time income
Barista number = the larger of Gap ÷ withdrawal rate and (Gap ÷ 12)·[1 − (1 + i)^−N] ÷ i + Full FIRE number ÷ (1 + i)^N, never above the full FIRE number
Go part-time in the first month k with P·(1+i)^k + S·((1+i)^k − 1) ÷ i ≥ that number with N − k months left
i = ((1 + nominal) ÷ (1 + inflation))^(1/12) − 1 a month; N = months until the part-time work ends
- Returns are real: 7.0% before inflation less 3.0% inflation is a 3.88% real return, so the numbers stay in today’s dollars.
- Part-time income is take-home pay, flat in today’s dollars, and stops at age 60. Spending is assumed to stay the same after that, and from then on the portfolio funds all of it at the 4.0% withdrawal rate.
- $4,300 a month is added at the end of each month until you go part-time; after that the part-time income is spent and nothing more is saved. The gap is paid from the portfolio, a twelfth at the end of each month.
- Returns are steady each year. Real markets are not, and the years you draw the gap are exposed to poor early returns, which is why the number is never less than the gap ÷ withdrawal rate.
- Spending is treated as after-tax spending and includes health insurance. Taxes on withdrawals are not modeled. Social Security and pensions are not counted, so the full FIRE number at the hand-off is cautious if a benefit will already be paying then.
- The search stops at 60 years; beyond that the result shows as not reached.
WORKED EXAMPLE · SAMPLE NUMBERS
Full FIRE number = $60,000 ÷ 4.0% = $1,500,000. Gap = $60,000 − $24,000 = $36,000 a year. Test 1: $36,000 ÷ 4.0% = $900,000. Test 2: paying $3,000 a month for 312 months (26 years) at a 3.88% real return, and holding $1,500,000 at the end, takes $1,150,088. The larger is $1,150,088, so the Barista number is $1,150,088. You have $420,000 and add $4,300 a month at a 3.88% real return. What is needed rises as the part-time years run down, so the first month your balance covers it is month 121 (10.1 years): $1,250,093 against $1,246,907.
SOURCES
[1]Determining Withdrawal Rates Using Historical DataBengen, Journal of Financial Planning, 1994
[2]Retirement Savings: Choosing a Withdrawal Rate That Is SustainableCooley, Hubbard & Walz (Trinity study), 1998
[3]The Theory of InterestIrving Fisher, Macmillan, 1930 (real versus nominal interest)
[4]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 Counsel[5]Original Medicare (Part A and B) Eligibility and EnrollmentCenters for Medicare & Medicaid ServicesHSBuilt by Hussain Sehorewala · checked against worked examples · Sep 29, 2026
Keep this number honest as your life changes.
Put it on your Money Map and it re-runs as you change the seven numbers. It stays in this browser, and the calculator stays free.
Questions about this result
Barista FIRE means leaving full-time work before you have a full FIRE number, and covering part of your spending with part-time work while your invested portfolio covers the rest, usually until an age when the portfolio can carry all of it. The name nods to the coffee-shop job people picture; it can be any work.
Two tests, and the larger one is the number. Test 1 is the gap divided by your withdrawal rate. Test 2 is the balance that pays the gap until the part-time work stops and is worth the full FIRE number when it does. Example: $50,000 of spending with $20,000 of part-time income, a 4% withdrawal rate, a 3.9% real return (7% before 3% inflation) and part-time work from age 45 to 60. Test 1 is ($50,000 − $20,000) ÷ 0.04 = $750,000. Test 2 is $1,048,079: enough to pay $30,000 a year for 15 years and still be worth the $1,250,000 full FIRE number at 60. The larger, $1,048,079, is the Barista number.
The number assumes it stops at the age you enter. From then on the portfolio has to fund all of your spending, so it has to be worth the full FIRE number at that moment; that is the second test above. A portfolio that only covers the gap at your withdrawal rate does not grow into the full number by itself: at the default 7% return and 3% inflation, drawing 4% of it a year leaves it roughly flat. Most Barista calculators stop at gap ÷ withdrawal rate ($900,000 for a $36,000 gap at 4%), which holds only if the part-time income lasts for life. Two ages are worth knowing: 62 is the earliest age Social Security retirement benefits can start, and 65 is when Medicare generally begins for most U.S. citizens and long-term residents (immigrants on visas may not qualify). This page does not count Social Security, so the full number at the hand-off age is a cautious one.
It depends on how long the work lasts. Part-time income only replaces the gap while it is paid, so each $1 of yearly income is worth the present value of that $1 a year for the years it lasts. In the example above, $10,000 a year for 15 years is worth about $114,000 today at a 3.9% real return. If the same income lasted for life, at a 4% withdrawal rate each $1 would replace $25, so $10,000 a year would replace $250,000.
Use take-home pay. Spending is what you actually pay out, so it should be compared with income after tax. This page also does not model tax on portfolio withdrawals; if most of your money is in pre-tax accounts, the real number is higher.
Only if you include it in your spending. A part-time job may not offer employer coverage, so it helps to price a marketplace plan into annual spending before reading the number. What a marketplace plan costs depends on household income, because the premium tax credit does. From 65, Medicare generally applies for most U.S. citizens and long-term residents.
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