Fat FIRE Calculator
Find the portfolio you need to retire on a comfortable, no-compromise income — and see your Lean, Regular and Fat FIRE numbers side by side at any safe withdrawal rate. Enter your spending and savings; the target, the age you'd reach it, and the exact formula update instantly. No sign-up.
Return & inflation assumptions
Returns are handled in real (after-inflation) terms, so every dollar shown is in today's money.
Lean vs Regular vs Fat FIRE — at your withdrawal rate
Same formula, three lifestyles. Your own spending decides which tier you're aiming at (highlighted).
| Tier | Annual spending | Portfolio needed |
|---|
Getting to your number
Green = your projected portfolio (today's dollars). Indigo = your FIRE target. Where they meet is the age you reach it.
How your monthly contribution moves the date
Everything else held equal — see how saving more or less shifts the age you hit your number.
| Monthly contribution | Reached at | From now |
|---|
The method — with your numbers
Your FIRE number is the portfolio at which safe withdrawals cover your spending. Reaching it is a projection of your current investments plus monthly contributions at a real (after-inflation) return.
At a 4% withdrawal rate this is the classic "25× spending" rule. A lower rate (more cautious) needs a bigger portfolio; a higher rate needs less but carries more risk of running out.
How to use this Fat FIRE calculator
- Annual spending. Enter the yearly income you want in retirement — Fat FIRE usually means $100,000 or more.
- Withdrawal rate. 4% is the common starting point (25× spending). Drop it to 3.5% or 3% to be more conservative and the target rises.
- Age, invested & monthly. Add what you have and what you save each month to see the age you'd reach the number.
What your number means
Fat FIRE isn't a different formula — it's the same maths at a higher spending level. Because the target scales directly with spending, a Fat FIRE lifestyle needs a much larger portfolio than Lean FIRE: at 4%, every extra $10,000 of annual spending adds $250,000 to the number. That's why the withdrawal rate and your savings rate matter so much at the top end.
If you'd rather stop saving early and let compounding finish the job, or bridge the gap with part-time work, those are the Coast and Barista FIRE strategies — see the guide and calculators below.
Frequently asked questions
What is Fat FIRE?
Financial independence with a comfortable, no-compromise lifestyle — typically $100,000+ of annual spending. Your Fat FIRE number is the portfolio needed so safe withdrawals cover that spending.
How is the Fat FIRE number calculated?
Annual spending ÷ safe withdrawal rate. At 4% that's 25× spending, so $120,000/yr needs $3,000,000. A lower rate like 3.5% needs more.
Is 4% still a safe withdrawal rate?
The 4% rule is a widely used starting point from historical studies, not a guarantee. Many Fat FIRE planners use 3.5% or 3% for a longer, more cautious retirement — this tool lets you set any rate.
Method & sources
- Calculation: FIRE number = annual spending ÷ safe withdrawal rate; the age you reach it is a month-by-month projection of current investments plus contributions at a real (after-inflation) return. Verified in an independent test suite.
- Concepts (Lean/Regular/Fat FIRE, safe withdrawal rate, 25× rule) follow standard FIRE-community definitions; figures are illustrative, not forecasts.
- Reviewed: · Assumptions reviewed quarterly.
Educational estimate, not financial advice. Investment returns are not guaranteed.