Size financial independence on a deliberately minimal spending level.
Lean FIRE applies the same arithmetic to a smaller budget, which cuts both the target and the time to reach it. The trade-off is a thinner margin for unexpected costs, since there is little discretionary spending left to cut. Lean FIRE is reached years earlier than full FIRE but leaves less flexibility, so the monthly budget figure is worth testing honestly before committing.
Lean FIRE
Lean FIRE number = lean annual spending ÷ withdrawal rate
Lean FIRE number = lean annual spending ÷ withdrawal rate Lean FIRE applies the same arithmetic to a smaller budget, which cuts both the target and the time to reach it. The trade-off is a thinner margin for unexpected costs, since there is little discretionary spending left to cut.
Lean FIRE is reached years earlier than full FIRE but leaves less flexibility, so the monthly budget figure is worth testing honestly before committing.
This calculator takes 5 inputs: Lean annual spending, Safe withdrawal rate, Current portfolio, Annual savings, Expected real return. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.