FIRE Calculator
Runs locallyInput stays in your browserFree, no sign-up
FIRE stands for financial independence, retire early, and it rests on one formula: FIRE number = annual spending × 25. The 25 comes from the 4% rule: withdrawing 4% of a portfolio each year covers spending while the portfolio lasts, and 1 ÷ 4% is 25. The rule comes from the Trinity study's backtests over 30-year retirements: a stock-and-bond portfolio with inflation-adjusted withdrawals survived most historical periods for the full 30 years.
Years to FIRE come from compounding. Annual savings = annual income − annual spending, and savings rate = annual savings ÷ annual income. Current savings plus annual savings then compound at the expected real return — return after inflation, default 5% — until they reach the FIRE number; that year count is the distance. With a 0% return the math collapses to a straight line: (FIRE number − current savings) ÷ annual savings. The intuition is that early years are dominated by your contributions while later years are dominated by compounding: at a 60% savings rate the portfolio crosses the halfway mark far sooner than the halfway point in time, which is why starting early beats saving more later.
An example: spending 120,000 a year, income 300,000, savings already 200,000, real return 5% — the FIRE number is 3,000,000, the savings rate 60%, annual savings 180,000, and the distance about 11.3 years. Savings rate is the lever that matters most: drop it to 30% under otherwise identical conditions and the distance stretches to about 28 years. Every 10,000 cut from spending lowers the FIRE number by 250,000. Change any input and the years recalculate at once, so you can see which variable moves the answer most.
The three tiers use the same spending at different multiples: Lean at 20× (tighter, sooner), Regular at 25× (the 4% rule standard), and Fat at 30× (roomier, later). Two boundaries matter. The 4% rule was tested for 30-year retirements with a stock-and-bond mix, not as a perpetual guarantee, and spending, income, and returns will all change — so the year count is an estimate under today's assumptions, not a promise. And it is arithmetic, not investment advice. If current savings already reach the target, the distance shows 0: the FIRE number is already met. If the distance looks too long, the levers in order of power are usually spending first, income second, and return assumptions last — raising an assumed return shortens the answer on paper without changing anything real, while cutting spending shrinks both the target and the time at once.
How to use
- Enter annual spending, estimated at the lifestyle you want to sustain after retiring.
- Enter annual income and current savings to get annual savings and the savings rate.
- Enter the expected annual real return, after inflation (default 5%).
- Read the FIRE number (spending × 25) and the years to reach it.
- Compare the Lean 20×, Regular 25×, and Fat 30× targets, pick one, and adjust the inputs.
FAQ
Where does 25× come from?
The 4% rule: withdrawing 4% of a portfolio a year covers spending, and 1 ÷ 4% is 25. It comes from the Trinity study's backtests over 30-year retirements.
Why does the savings rate matter so much?
A higher rate means more saved each year and fewer years to go: about 11 years at a 60% savings rate, about 28 years at 30%. Change income or spending in the tool and watch it move.
Is the 5% return guaranteed?
No, it is an assumption. Try 3% or 7% and see how the years change — never treat an assumption as a promise.
What if I have already saved enough?
The distance shows 0, meaning the FIRE number is already met.
How do I pick Lean, Regular, or Fat?
They are 20×, 25×, and 30× the same spending: Lean is sooner but tighter, Fat is roomier but later, Regular is the 4% rule standard.