“FIRE” stands for financial independence, retire early. The classic version asks you to save a portfolio large enough to cover all your spending forever. Two popular variants lower that bar in different ways. Coast FIRE means you have saved enough that growth alone will reach your full target by a normal retirement age, so you can stop saving. Barista FIRE means you have saved enough that a part-time job plus portfolio withdrawals can cover your spending now.
They sound similar, but they answer different questions and use different math. This guide puts both side by side, using the formulas inside our Coast FIRE calculator and Barista FIRE calculator. All figures come from running that code with example inputs for one hypothetical household.
Start with the full FIRE number
Both variants are measured against the same baseline: the portfolio that covers your annual spending at a chosen withdrawal rate.
Using example inputs of $50,000 a year in expenses and a 4% withdrawal rate, the full FIRE number is $1,250,000. The 4% figure comes from research on historical U.S. market returns over 30-year retirements. It is a planning rule of thumb, not a guarantee, and many early retirees use a lower rate for longer horizons. Both calculators let you change it.
Coast FIRE: letting time do the work
Coast FIRE asks: how much do I need invested today so that, with no more contributions, compound growth reaches my full FIRE number by my chosen retirement age? The answer is just a present-value calculation:
Here r is the real (after-inflation) annual return, so the target stays in today’s dollars. If you enter a nominal return and an inflation rate instead, the calculator converts them with the Fisher equation, r = (1 + nominal) ÷ (1 + inflation) − 1.
Worked example
Example inputs: age 30, retirement at 60 (30 years), $50,000 expenses, 4% withdrawal rate, a 5% real return, and $100,000 already invested.
(1.05)^30 ≈ 4.322, so the Coast FIRE number is $1,250,000 ÷ 4.322 ≈ $289,222. With $100,000 saved, this household is 34.6% of the way to Coast FIRE.
The real-return assumption dominates
Because the formula raises (1 + r) to the 30th power, small changes in the assumed return move the answer a lot. Same household, different example return assumptions:
| Real return (example) | Coast FIRE number at 30 | Coast age while adding $1,000/mo |
|---|---|---|
| 4% | $385,398 | 60 |
| 5% | $289,222 | 60 |
| 6% | $217,638 | 45 |
| 7% | $164,209 | 37 |
Going from a 4% to a 7% real return cuts the required amount by more than half. That is the main reason to run Coast FIRE numbers with a conservative return, and to re-check them every year as real results come in.
The moving target
The required coast amount isn’t fixed. Each year closer to retirement, there is one fewer year of growth, so the required balance rises. The calculator projects two paths. One is a “coasting” balance that only grows. The other is a “contributing” balance that also adds the monthly contribution. It reports the first age at which the contributing balance catches up with that year’s required number. Here is the 5% example, with $1,000 a month going in:
| Age | Coasting only | With $1,000/mo | Required coast number |
|---|---|---|---|
| 30 | $100,000 | $100,000 | $289,222 |
| 35 | $127,628 | $195,718 | $369,128 |
| 40 | $162,889 | $317,882 | $471,112 |
| 45 | $207,893 | $473,796 | $601,271 |
| 50 | $265,330 | $672,788 | $767,392 |
| 55 | $338,635 | $926,756 | $979,408 |
| 60 | $432,194 | $1,250,892 | $1,250,000 |
In this example the contributing path only reaches the required number at age 60. At $1,000 a month on a $100,000 start, the household never gets ahead of the curve early. It simply reaches the full target at 60. That is a useful, honest result: Coast FIRE is not automatic, and it depends heavily on how large your early savings are relative to your spending.
Barista FIRE: shrinking the target with part-time income
Barista FIRE asks a different question: if part-time work covers some of my spending, how big does the portfolio need to be to cover the rest? The name comes from the idea of a part-time job that might also offer benefits. The math is just the full FIRE formula applied to the gap:
Barista FIRE number = portfolio draw ÷ withdrawal rate
Because the formula is linear, every $1,000 of reliable part-time income lowers the required portfolio by $1,000 ÷ 0.04 = $25,000 at a 4% withdrawal rate.
Worked example
Example inputs: the same $50,000 of expenses and 4% withdrawal rate. The household is 30 with $100,000 invested, saves $1,000 a month, assumes a 5% annual return, and wants to switch to part-time work at 40. The calculator grows savings with monthly compounding:
That gives a projected portfolio of $319,983 at age 40. Here is how much part-time income changes the picture:
| Part-time income (example) | Portfolio needed | Smaller than full FIRE by | Gap at age 40 |
|---|---|---|---|
| $0 | $1,250,000 | 0% | −$930,017 |
| $15,000 | $875,000 | 30% | −$555,017 |
| $25,000 | $625,000 | 50% | −$305,017 |
| $35,000 | $375,000 | 70% | −$55,017 |
Even $35,000 of part-time income leaves this household $55,017 short at 40 under these inputs. The table shows the trade-off clearly. Barista FIRE can cut the required portfolio dramatically, but only to the extent that the part-time income is dependable.
Side by side
| Coast FIRE | Barista FIRE | |
|---|---|---|
| Question it answers | When can I stop saving? | When can I stop full-time work? |
| Core formula | target ÷ (1 + r)^years | (expenses − part-time income) ÷ withdrawal rate |
| Still working? | Yes, enough to cover current spending | Yes, part-time |
| Portfolio withdrawals start | At traditional retirement | Immediately, for the gap |
| Most sensitive to | Assumed return and years remaining | Reliability of part-time income, withdrawal rate |
| Example result above | $289,222 needed at 30 | $625,000 needed at 40 with $25k income |
The two can also be combined. A common sequence is to reach Coast FIRE, then switch to lower-paid or part-time work that covers living costs. That is effectively Barista FIRE with zero withdrawals until the portfolio finishes coasting.
Timing the switch
For barista FIRE, the age you switch to part-time work matters as much as the part-time income. Same example household, still planning on $25,000 of part-time income, but switching at different ages:
| Switch age (example) | Projected portfolio | Barista FIRE number | Surplus or gap |
|---|---|---|---|
| 40 | $319,983 | $625,000 | −$305,017 |
| 45 | $478,659 | $625,000 | −$146,341 |
| 50 | $682,298 | $625,000 | +$57,298 |
| 55 | $943,639 | $625,000 | +$318,639 |
Under these inputs, the first switch age in the table that clears the target is 50. Each extra year of full-time work helps in two ways: it adds another year of contributions and another year of growth on a larger balance. That is the same compounding effect that drives coast FIRE, which is why the two strategies often blend together in practice. It also means that a delay of a few years can turn a plan that does not quite work into one that comfortably does, as the jump between the switch ages of 45 and 50 shows in this example.
Where these fit among FIRE styles
Coast and barista FIRE are often described as middle paths between working a traditional career to a normal retirement age and full early retirement. Full FIRE can itself be planned at different spending levels, from a frugal lean budget to a generous fat budget; our guide on lean FIRE vs fat FIRE compares those targets and timelines. All of these approaches rely on a withdrawal rate to turn spending into a portfolio target, so the choice of rate matters a great deal. Our safe withdrawal rate guide explains where the 4% figure comes from, why longer retirements often use lower rates, and how sequence of returns risk affects anyone drawing down a portfolio, including barista FIRE households who start withdrawals early.
One practical advantage of both middle paths is flexibility. A coaster who still earns enough to cover expenses never has to sell investments during a market downturn. A barista FIRE household with dependable part-time income needs only a small withdrawal, so a bad year in the markets has less effect on the portfolio than it would for a fully retired household drawing the entire budget. That reduced exposure to sequence of returns risk is a real benefit that the simple formulas above do not show.
The trade-off is that both paths depend on continued work. Health, local job markets, caregiving responsibilities and personal motivation can all change over a decade or two. Before relying on either plan, consider what you would do if part-time income stopped for a year, and whether you could fall back to full-time work, reduce spending, or draw more from the portfolio temporarily. Keeping a cash reserve, sized with our emergency fund calculator, gives you time to adjust without selling investments at a poor moment.
Risks the formulas leave out
- Sequence of returns. Both calculators use a constant return. A bad market in the first years of withdrawals hurts far more than the same drop later. Barista FIRE, which starts withdrawals early, is more exposed to this.
- Health insurance. In the U.S., leaving full-time work often means paying for coverage yourself. Put that cost into your expense number rather than assuming it away.
- Inflation. Using a real return keeps targets in today’s dollars. If you use a nominal return, raise the expense figure for inflation too. Our inflation calculator helps with that conversion.
- Taxes and Social Security. Neither calculator models taxes on withdrawals or future benefits. Both can change the real target meaningfully.
Computing your own numbers, step by step
You can do both calculations with a pencil and a basic calculator before you open any tool. Doing it once by hand makes the calculator’s output much easier to trust and to question.
- Pin down annual spending. Use what you actually spend, not your income. Include things that change after leaving full-time work, such as health insurance, commuting costs that disappear, and any retirement-account contributions you will stop making.
- Pick a withdrawal rate. Divide spending by it to get the full FIRE number. A lower rate, such as 3.5%, gives a bigger and more cautious target.
- For Coast FIRE, choose a real return and count the years. Compute (1 + r)^years with your calculator’s power key and divide the full target by it. Compare the result with what you have invested today.
- For Barista FIRE, subtract the part-time income you are confident of. Divide what is left by the withdrawal rate. Then estimate where your savings will be on the date you want to cut back, and compare.
- Repeat with worse assumptions. Lower the return by one or two points and cut the part-time income. If the plan still works, it is resilient. If not, you know which assumption it depends on.
Common mistakes
- Mixing real and nominal numbers. Using a nominal 8% return with today’s spending makes the target look far too easy, because the spending figure is in today’s dollars while the growth is not. Pick one and stay consistent.
- Counting home equity. FIRE numbers refer to assets that can fund withdrawals. A paid-off home lowers your spending, which is how it should enter the math, but it doesn’t generate cash to withdraw.
- Treating Coast FIRE as permanent. If markets fall soon after you stop saving, you may slip back below the coast line. Re-run the numbers each year.
- Overestimating part-time income. The Barista formula is linear, so every dollar of income you overestimate becomes 25 dollars (at 4%) of missing portfolio.
How to use these numbers
Treat both outputs as ranges, not answers. Run the Coast FIRE calculator at a low, medium and high real return. Run the Barista FIRE calculator with the part-time income you are confident of, not the most you could earn. If both pessimistic cases still work, you have a robust plan. If only the optimistic ones work, the gap tells you how much more to save or how much spending to trim. For a quick sense of how fast money grows at a given rate, see how accurate the Rule of 72 is.
