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How much do you need for a lean retirement?

Lean FIRE targets a smaller, minimalist retirement budget — so the number is smaller and the date comes sooner. See yours, and the odds it lasts, updating as you type.

Your Lean FIRE number

$750,000

$30,000/yr ÷ 4%

Earliest you can retire

Age 46

≈ 2036 · in ~10 yrs

Money lasts to 95

84%

of 1,000 simulations

$0$1M$2M$3Mage 40age 50age 60age 70Lean FIRE · $750kretire 45worst 10% runs dry ~74

1,000 simulated futures · 7% real return, 15% volatility · drawn down to age 95

Save this plan — freeRuns in your browser · nothing is stored until you sign up

Not financial advice — a projection from your own assumptions.

What is Lean FIRE?

Lean FIRE is financial independence on a deliberately modest budget — the retirement equivalent of a minimalist lifestyle. Instead of assuming a typical American household's spending, a lean planner keeps costs low (a paid-off home, simple food, limited travel) so the portfolio it takes to cover them is smaller too. Because a FIRE number is just spending capitalized at a withdrawal rate, cutting the spending cuts the number directly — often by a third or more.

The Lean FIRE formula

The same formula every FIRE calculator uses, just with a smaller spending figure:

lean FIRE number = lean annual spending ÷ safe withdrawal rate

Worked example: $30,000 a year of lean spending at a 4% withdrawal rate needs $30,000 ÷ 4% = $750,000 — versus $1,250,000 for a $50,000/yr standard plan. Every formula is on the methodology page.

Lean FIRE vs. Fat FIRE

Lean and Fat FIRE are the two ends of the same spectrum — the exact same formula, applied to a smaller or bigger spending figure. Lean FIRE trades comfort for an earlier date; Fat FIRE trades a longer wait for a richer retirement. If a no-compromise budget is more your speed, the Fat FIRE calculator runs the same math the other direction, and the full FIRE calculator uses a typical middle-of-the-road spending figure.

Beyond a one-time estimate

A lean budget still needs watching.

Save the plan and your number, your date, and the odds re-check themselves against your real accounts — free.

Runs on your real money

Link a brokerage with SnapTrade or Plaid, or drop in a CSV, and this exact chart tracks your actual balances — updating as markets move and you invest. No more re-typing estimates.

Tells you if you’re on track

Your Readiness score re-runs this Monte Carlo on your real net worth and answers what matters: on track for your age, will it last, is your emergency fund covered.

Your whole net worth, in one place

Investments, cash, property and debts together — with a savings rate pulled from your real deposits and your dividend income counted. All free.

Same math here and inside — every formula is hand-checkable on the methodology page.

Lean FIRE calculator questions

What is Lean FIRE?
Lean FIRE means retiring on a deliberately modest, minimalist budget — often 50–70% of what a typical retirement plan assumes. Because your FIRE number is just capitalized spending, a smaller budget means a smaller number, reached years sooner than a standard plan.
How is the Lean FIRE number calculated?
The same formula as any FIRE number: annual spending ÷ your safe withdrawal rate. Lean FIRE just plugs in a lower spending figure. Spending $30,000 a year at a 4% withdrawal rate needs $30,000 ÷ 4% = $750,000 — well under the $1,250,000 a $50,000/yr plan needs.
How much should I plan to spend on Lean FIRE?
There’s no fixed rule, but many lean planners target somewhere around 50–70% of a typical retirement budget — enough to cover housing, food, and healthcare without the extras. Set the spending field to whatever your own lean budget actually is; the number and date update instantly.
Is Lean FIRE too risky?
A tighter budget leaves less room to absorb a bad market early in retirement, which is exactly what the Monte Carlo simulation above is for — it reports the odds your money lasts against 1,000 simulated market paths, not just a single average return.
What’s the difference between Lean FIRE and Fat FIRE?
They’re opposite ends of the same spectrum: Lean FIRE targets a smaller, minimalist budget for an earlier number; Fat FIRE targets a bigger, no-compromise budget for a richer retirement. Both use the exact same 25×-style formula — just a different spending figure.
What return should I assume?
A real (after-inflation) return, so every figure stays in today’s dollars. 7% roughly matches the long-run US stock market; try 5% to be conservative.

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FIRE retirement calculator →FIRE number calculator →Fat FIRE calculator →Coast FIRE calculator →Barista FIRE calculator →

Weighing up the options? See how the best FIRE calculators compare.

A lean number still moves with the market.

Link your brokerage or drop in a CSV, and Fire Horizon re-checks whether your lean plan is still on track on your real balances — every day, for free.

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