Lean FIRE Calculator

Estimate your Lean FIRE number and how long it takes to get there—then visualize the journey.

Your numbers

Current age

Currency

Current invested net worth (portfolio)

Exclude home equity unless you plan to sell/use it to fund retirement.

Monthly take-home income

Monthly spending now

Lean retirement spending (monthly)

This drives your Lean FIRE number (target portfolio).

Other retirement income (monthly)

Optional: part-time work, rentals, pensions, etc.

One-time expense at/near retirement (optional)

Example: move abroad costs, healthcare buffer, debt payoff, vehicle purchase.

How you save

Auto: invest (income − spending) Manual monthly contribution

Monthly invested contribution (manual mode)

Contribution growth (annual %)

Optional: if you plan to increase contributions over time.

Assumptions (advanced)

Expected annual return (%)

Inflation (%)

Income growth (annual %)

Spending growth (annual %)

Withdrawal rate in retirement (%)

4% ≈ 25× annual spending.

Your “Lean” spend cap (monthly)

Used only for the Lean/Not-lean badge.

Show results in today’s dollars (inflation-adjusted)

If checked: subtracts inflation from rates so projections are in today’s purchasing power.

Disclosure: Educational tool only. Not investment, tax, or legal advice. Results are estimates; markets and inflation are uncertain.

Results

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Lean FIRE number (target portfolio)

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Projected portfolio at FI

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Estimated FI age

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Time to FI

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Est. retirement month: —

Monthly savings (today)

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Savings rate (today)

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Portfolio projection (principal vs growth). The target line becomes a shaded “FI zone” after you reach it.

Year	Age	End portfolio	Contrib (year)	Growth (year)	% of target

How the target is calculated: (Annual retirement spending − other annual retirement income) ÷ withdrawal rate, plus any one-time expense.

Stop guessing. Stress test your plan for 50 years.

Build your FIRE number, then pressure test withdrawals across inflation and ugly sequences.

PASS/FAIL + ruin year
Inflation plus real return sequences
One-time expense shocks

Includes the FIRE Number Builder, 50-year Stress Test, and the IPS rulebook.

Get the FIRE Starter Kit

ABOUT THE AUTHOR

Carlos Grider launched A Brother Abroad in 2017 after a “one-year abroad” experiment turned into a long-term life strategy. After 65+ countries and a decade abroad, he now writes about FIRE, personal finance, geo-arbitrage, and the real-world logistics of living abroad—visas, costs, and tradeoffs—so readers can make smarter global moves with fewer surprises. Carlos is a former Big 4 management consultant and DoD cultural advisor with an MBA (UT Austin) and Boston University’s Certificate in Financial Planning. He’s the author of Digital Nomad Nation: Rise of the Borderless Generation and is currently writing The Sovereign Expat.

Click here to learn more about Carlos's story.