Lean FIRE Calculator

Size financial independence on a deliberately minimal spending level.

About Lean FIRE Calculator

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.

Formula

Lean FIRE

Lean FIRE number = lean annual spending ÷ withdrawal rate

lean spending: A deliberately minimal budget covering essentials and little else

Worked example

With the default values below, Lean FIRE Calculator returns Lean FIRE Number of $600,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lean annual spendingminimum 0: 24,000
Safe withdrawal rateaccepts 0–100 %: 4 %
Current portfoliominimum 0: 150,000
Annual savingsminimum 0: 20,000
Expected real returnaccepts 0.1–20 %: 5 %

Results

Lean FIRE Number: $600,000.00
Years to Lean FIRE: 12.3 years
Monthly Budget It Supports: $2,000.00
Still Needed: $450,000.00
Progress: 25.0%

Step by step

1Values used
2Lean FIRE
3Lean FIRE Number= 600,000.00
4Years to Lean FIRE= 12.3 years
5Monthly Budget It Supports= 2,000.00
6Still Needed= 450,000.00
7Progress= 25.0

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation or tax into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This is an estimate for general information and not professional financial, tax or legal advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Lean FIRE calculated?

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.

Why does Lean FIRE matter?

Lean FIRE is reached years earlier than full FIRE but leaves less flexibility, so the monthly budget figure is worth testing honestly before committing.

What values do I need to enter?

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.