— Retirement & FIRE
Lean FIRE Calculator
Calculate the FIRE number for a deliberately frugal budget. Enter bare-bones expenses, savings, return, and withdrawal rate to see the lean FIRE corpus, years to reach it, progress, and how relocation, savings rate, or medical buffers affect the target.
Years to lean FIRE
20 yrs 8 mos
- Lean FIRE number
- $750,000
- Progress to lean FIRE
- 5.33%
- Lean FIRE age
- 51
- Regular FIRE number
- $1,125,000
- Fat FIRE number
- $1,875,000
- Lean number (nominal at FIRE)
- $1,249,973.96
Try: Lean FIRE on $30k a year, By savings rate (40%), Relocate (20% cheaper), Cautious 3.5% + healthcare buffer
— Accumulation to the lean-FIRE number
| Age | Savings | Growth | Corpus | Lean number |
|---|---|---|---|---|
| 30 | $0 | $0 | $40,000 | $750,000 |
| 31 | $20,000 | $1,756 | $61,756 | $750,000 |
| 32 | $20,000 | $2,711 | $84,467 | $750,000 |
| 33 | $20,000 | $3,708 | $108,176 | $750,000 |
| 34 | $20,000 | $4,749 | $132,925 | $750,000 |
| 35 | $20,000 | $5,836 | $158,761 | $750,000 |
| 36 | $20,000 | $6,970 | $185,731 | $750,000 |
| 37 | $20,000 | $8,154 | $213,885 | $750,000 |
| 38 | $20,000 | $9,390 | $243,275 | $750,000 |
| 39 | $20,000 | $10,680 | $273,955 | $750,000 |
| 40 | $20,000 | $12,027 | $305,982 | $750,000 |
| 41 | $20,000 | $13,433 | $339,416 | $750,000 |
| 42 | $20,000 | $14,901 | $374,317 | $750,000 |
| 43 | $20,000 | $16,433 | $410,750 | $750,000 |
| 44 | $20,000 | $18,033 | $448,783 | $750,000 |
| 45 | $20,000 | $19,703 | $488,486 | $750,000 |
| 46 | $20,000 | $21,446 | $529,932 | $750,000 |
| 47 | $20,000 | $23,265 | $573,197 | $750,000 |
| 48 | $20,000 | $25,165 | $618,362 | $750,000 |
| 49 | $20,000 | $27,148 | $665,509 | $750,000 |
| 50 | $20,000 | $29,217 | $714,727 | $750,000 |
| 51 | $20,000 | $31,378 | $766,105 | $750,000 |
— Crossover to the lean-FIRE number
Download— How it works
Lean FIRE number = lean annual expenses ÷ safe withdrawal rate (×25 at 4%). Geographic arbitrage cuts the expenses first; other income reduces them further; a healthcare buffer is added on top. Your savings then grow at the real return until the corpus reaches the number.
A smaller number, a faster finish
Lean FIRE uses the same engine as any FIRE calculation — expenses ÷ a safe withdrawal rate — but on a deliberately frugal budget. Because the target scales directly with spending, a lean lifestyle cuts the number sharply: at 4%, $30,000 of expenses needs $750,000, while $60,000 needs $1.5 million. And living lean usually means saving a high share of income, so you reach the smaller target far faster. The calculator shows the years, your lean-FIRE age and progress, with the regular and fat FIRE numbers alongside for context.
Worked example — age 30, $30,000 lean expenses, $40,000 saved, $20,000/year invested, 7% return: Lean FIRE number = $30,000 × 25 = $750,000; reached in about 21 years. Regular FIRE (≈ $45k spending) would be $1,125,000; fat FIRE (≈ $75k) would be $1,875,000.
Geographic arbitrage and other income
Two levers shrink the number further. Geographic arbitrage — relocating to a lower-cost city or country — cuts your expenses directly, and because the number is 25× expenses, a 20% cost cut lops 20% off the target. Other income works the same way: a small pension, Social Security or part-time work (barista-lean) covers part of your spending, so your savings only have to fund the rest. Together they can bring lean FIRE within a handful of years for a committed saver.
The thin-margin risk
Lean FIRE’s strength — a small budget — is also its danger. With little slack, an unexpected cost, a stretch of high inflation, or a bad run of early markets (sequence-of-returns risk) can force you back to work or below a comfortable standard of living. Healthcare is the classic exposure, especially before state or Medicare coverage. That’s why a contingency buffer matters and why many lean-FIRE planners use a more conservative 3–3.5% withdrawal rate. Add a buffer here and treat a lean plan that only just works as one that needs more margin.
— Reader questions
What is the lean FIRE number?
Your bare-bones annual expenses divided by your safe withdrawal rate — 25× at 4%. So $30,000 of frugal spending gives a $750,000 lean FIRE number, well below a regular or fat FIRE target.
How is lean FIRE different from regular and fat FIRE?
They differ only in the spending assumption. Lean FIRE funds a frugal budget, regular FIRE a typical one (roughly 1.5× lean), and fat FIRE a comfortable one (around 2.5× lean). The calculator shows all three numbers side by side.
How does relocating help?
Geographic arbitrage cuts your expenses, and since the target is 25× expenses, every dollar of spending you cut removes about 25 dollars from the number. A 20% cost reduction shrinks the lean FIRE number by 20%.
Is lean FIRE risky?
It carries more risk than fatter plans because the budget has little slack. An emergency, high inflation, or poor early returns can break it. A healthcare/contingency buffer and a lower withdrawal rate (3–3.5%) help guard against that.
Why does the savings rate matter so much for lean FIRE?
Living frugally both lowers the target and frees up a large share of income to invest — the same habit works on both ends. That double effect is why lean FIRE can be reached unusually fast.