Calculator
FIRE number calculator
How large a portfolio your spending requires, and how long it takes to get there at your current savings rate — measured in today's dollars throughout.
The 4% figure comes from studies of 30-year US retirements in the twentieth century. It was never a law, it assumes a specific stock and bond mix, and it can fail if the first few years of your retirement are bad ones — the sequence of returns matters as much as the average. Treat 4% as one scenario, not the answer, and run 3.5% to see how much the target moves.
How this is calculated
- Target =
(annual spending − other income) / withdrawal rate. - The projection compounds your current savings at the real return and adds annual savings at the end of each year, so every figure on this page is already in today's dollars. No separate inflation adjustment is applied or needed.
- Contributions are held flat in real terms — the model assumes your savings keep pace with inflation but do not otherwise grow.
- Taxes on withdrawals are not modelled. If your savings sit in a pre-tax account, the portfolio you need is larger than shown.
The savings rate does the heavy lifting
Change the return assumption by a point and the timeline shifts by a year or two. Change the savings rate by ten points and it shifts by the better part of a decade. This is the counter-intuitive part of early retirement arithmetic: saving more does double duty, because every dollar you do not spend both grows the portfolio and shrinks the target the portfolio has to hit.
That is also the honest caveat on the whole exercise. A plan that depends on a 60% savings rate is a plan that depends on your income and your circumstances holding steady for a decade. Build in more margin than the arithmetic says you need.
Common questions
What is a FIRE number?
The size of invested portfolio that can fund your annual spending indefinitely at a chosen withdrawal rate. At a 4% withdrawal rate it works out to 25 times your annual spending; at 3.5% it is roughly 28.5 times.
Is the 4% rule still valid?
It remains a reasonable starting point but it was derived from historical 30-year US retirements and is not a guarantee. Longer retirements, higher valuations at the start, or a poor first decade of returns all argue for a lower rate. Running 3.5% alongside 4% shows how sensitive the target is.
Should I use a nominal or real return here?
Real. This calculator works entirely in today's dollars, so entering a nominal return would double-count inflation and make the timeline look far shorter than it is.
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