Lean FIRE is financial independence on a frugal budget — typically under $40K/year in the US. It's popular with minimalists, geographic arbitrage practitioners, and those who find contentment in simplicity. The lower spending target means a much smaller required portfolio.

What is the lean FIRE number for $30K/year spending?

At 25× annual spending: $30,000 × 25 = $750,000. At $25K/year: $625,000. At $40K/year: $1,000,000. These are the 4% rule targets. VPW requires somewhat less.

Lean FIRE has higher sequence-of-returns risk because there's little room to cut spending further in bad markets. Aiming for a 90–95% success rate (rather than the typical 85% for normal FIRE) adds an important buffer. The Monte Carlo simulation here shows you exactly where you stand.

Can lean FIRE work for 40+ year retirements?

Yes — the 4% rule was originally tested over 30-year periods, but historical data suggests it holds well over 40–50 year periods too, especially at lower withdrawal rates (3.5% or below). This tool simulates to age 95 (60-year horizon for a 35-year-old retiree) using all available historical data.

Lean FIRE Calculator

Model early retirement on a lean $25K–$40K/year budget. Monte Carlo simulation shows your probability of success at a frugal spending level.

What it does

Lean spending presets

Pre-configured for $2,500/month ($30K/year) — the typical lean FIRE benchmark. Adjust to your specific budget.

Long-horizon simulation

Lean FIRE often means 40–50 year retirements. The simulation runs to age 95 to test this extended period.

FIRE number display

Shows lean, regular, and fat FIRE numbers side by side so you can see the difference your spending target makes.

How to use Lean FIRE Calculator

1
Review the lean FIRE defaults
The calculator pre-fills $2,500/month ($30K/year) spending — adjust up or down to match your actual lean budget.
2
Set your current situation
Enter your age, current portfolio, and monthly savings rate. Lean FIRE practitioners often have high savings rates.
3
Read your lean FIRE number
At $30K/year spending, your FIRE number is $750K (25×). Lower spending dramatically reduces what you need.
4
Check success probability
A lean budget leaves little room for bad market sequences. 90%+ success rate recommended for lean FIRE given the long horizon.

When to use this

How does lean FIRE compare to regular FIRE?

Switch between lean ($2,500/mo) and regular ($5,000/mo) spending presets and compare the FIRE numbers and success rates.

Can I retire at 40 on a lean budget?

Set retirement age to 40 and see what portfolio size achieves 90%+ success over a 55-year horizon.

Technical details

Default spending	$2,500/month ($30,000/year) in today's dollars — lean FIRE benchmark
Simulation horizon	To age 95 by default — a 55-year retirement for someone retiring at 40
Monte Carlo	5,000 paths, Shiller 1928–2024 bootstrap, all browser-side

Frequently Asked Questions

What is Lean FIRE?: Lean FIRE is financial independence on a frugal budget — typically under $40K/year in the US. It's popular with minimalists, geographic arbitrage practitioners, and those who find contentment in simplicity. The lower spending target means a much smaller required portfolio.
What is the lean FIRE number for $30K/year spending?: At 25× annual spending: $30,000 × 25 = $750,000. At $25K/year: $625,000. At $40K/year: $1,000,000. These are the 4% rule targets. VPW requires somewhat less.
Is lean FIRE risky?: Lean FIRE has higher sequence-of-returns risk because there's little room to cut spending further in bad markets. Aiming for a 90–95% success rate (rather than the typical 85% for normal FIRE) adds an important buffer. The Monte Carlo simulation here shows you exactly where you stand.
Can lean FIRE work for 40+ year retirements?: Yes — the 4% rule was originally tested over 30-year periods, but historical data suggests it holds well over 40–50 year periods too, especially at lower withdrawal rates (3.5% or below). This tool simulates to age 95 (60-year horizon for a 35-year-old retiree) using all available historical data.

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