Lean FIRE Calculator

At a 4% withdrawal rate, $600,000 supports $24,000 of spending a year ($600,000 × 4%), or $2,000 a month. That sits just under the $25,000 floor most people use to define lean FIRE, so retiring on $600,000 is possible but only with genuinely minimal fixed costs — typically a paid-off home or a low-cost-of-living area, no car payment, and cheap hobbies. Run the math the other way to check yourself: if you can honestly live on $24,000 a year, your lean FIRE number is exactly $600,000 ($24,000 × 25). Any recurring cost you can't control, like rent in a rising market, argues for a bigger cushion.

A $25,000 annual budget works out to about $2,083 a month ($25,000 ÷ 12) and requires a $625,000 portfolio under the 4% rule ($25,000 × 25). Whether it's enough depends less on discipline than on structure: retirees who own their housing outright and live where property taxes and insurance are cheap routinely spend under this line, while renters in metro areas almost never do. Health insurance is usually the swing item — at that income level, US marketplace subsidies often cut premiums substantially, which is a large part of why $25,000 budgets pencil out.

Lean FIRE for a couple usually means a shared budget of around $45,000 rather than double an individual's $25,000, because housing, utilities, insurance, and vehicles are shared. At the 4% rule, a $45,000 joint budget requires $1,125,000 ($45,000 × 25) — about $3,750 a month for two people ($45,000 ÷ 12), versus $2,083 a month for a solo retiree on $25,000. Because the second person adds far less than double the cost, couples often reach lean FIRE with meaningfully less saved per person than singles at the same standard of living.

Every $1,000 of annual spending you permanently remove takes $25,000 off the portfolio you need at a 4% withdrawal rate. Trimming a planned budget from $60,000 to $35,000 a year drops the target from $1,500,000 to $875,000 — a $625,000 difference that can easily represent a decade or more of additional saving and compounding. This is the core lean FIRE trade: expense cuts work on both sides of the ledger at once, freeing more money to invest today while shrinking the finish line it has to reach.