Annual spending ÷ safe withdrawal rate: the pot that can fund that spending indefinitely. At the classic 4% rule that is 25× annual spending.
Savings and contributions grow at your return after inflation until they cross the number. The target is priced today, so only growth beyond rising prices counts.
The biggest lever: it grows the pot faster and shrinks the number you are aiming for, since saving more usually means spending less.
Enough saved that growth alone finishes the job by retirement age. Lean FIRE targets minimal spending for an earlier date; Fat FIRE a bigger number for a costlier life.
The same average return, in a different order, over a 30-year retirement from $1M drawing $40k a year. A bad run right after you retire can permanently damage a portfolio; this tool assumes a smooth, constant return, which real markets never deliver.
Dropping from a 4% to a 3.5% withdrawal rate does not sound like much, but it raises your FIRE number by roughly 14%: a meaningfully bigger pot for the same spending, in exchange for a larger safety margin.
The amount you'd need today such that, with zero further contributions, investment growth alone carries you to your FIRE number by a chosen retirement age. Once you've coasted past that number, every future dollar you save is optional — growth alone finishes the job.
A higher savings rate does two things at once: it grows your pot faster and shrinks the pot you actually need (since your target spending falls too). A higher return rate only does the first. That's why FIRE advice leans so heavily on the savings rate over chasing extra investment return.
The 4% rule comes from historical US market backtests (the Trinity study) over a roughly 30-year retirement. Longer retirements, non-US markets, or a desire for more safety margin argue for a lower rate (3–3.5%); shorter horizons or more flexibility in spending can support a higher one. It's a starting point, not a law.
No — this is a pre-tax projection in today's money: returns are reduced by the inflation you set, contributions are assumed to rise with prices, and the FIRE number is what your spending costs now. Real-world results depend heavily on account type (taxable, tax-deferred, Roth) and your tax situation at withdrawal, which this tool doesn't model.
Because you're withdrawing money while the market moves, not just watching a balance grow. A crash early in retirement forces you to sell a lot of shares while they're cheap to fund the same withdrawal, which permanently shrinks the base that's left to recover — the exact same crash landing near the end barely matters, because there's far less time left for it to compound against you. The average return genuinely doesn't tell you what you need to know; the order does.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.