Lean FIRE Calculator
Find your Lean FIRE number by building it from the spending floor rather than guessing a total. Enter what each category actually costs you per year and the calculator shows the portfolio each one requires on its own, so you can see which expense is really setting your retirement date. A Lean FIRE plan lives or dies on the accuracy of these five numbers.
A spending floor of $12,000 housing, $5,000 food, $6,000 healthcare, $3,000 transport and $4,000 other comes to $30,000 a year, a $750,000 Lean FIRE number at a 4% withdrawal rate. Housing alone accounts for $300,000 of that, which is why moving somewhere cheaper moves a Lean FIRE date more than any other single decision.
Enter Your Spending Floor
Annual cost per category, in today's dollarsResults
Your spending floor and what each category costs youEnter your annual costs and click calculate to see which expense is setting your retirement date.
Frequently Asked Questions
Understanding the Lean FIRE target
What is Lean FIRE?
Lean FIRE is financial independence at a deliberately minimal spending level, commonly under $40,000 a year for a household. Because the FI number is a multiple of spending, cutting the spending floor cuts the target proportionally: every $1,000 a year removed from the floor removes $25,000 from the portfolio you need at a 4% withdrawal rate.
That leverage is what makes Lean FIRE reachable years earlier than a conventional plan, and it is also what makes the estimate fragile, since the same leverage works in reverse when a cost turns out higher than assumed.
Why enter costs by category?
A single spending total hides where the money goes, and the FI number is the sum of five independent targets. Seeing that housing requires $300,000 of portfolio on its own, while transport requires $75,000, tells you which change actually moves the retirement date and which is rounding error.
It also makes the estimate auditable. A total pulled from memory tends to be optimistic; five categories checked against a year of statements tends not to be.
Why is healthcare the risky line?
Employer coverage hides most of its cost in the employer's contribution, so the payroll deduction is a poor guide to what the same coverage costs when you buy it yourself. Healthcare is also the category most likely to rise faster than general inflation and least likely to be cuttable in a bad year.
A Lean FIRE plan with an understated healthcare line is not slightly wrong, it is wrong by 25 times the annual shortfall in portfolio terms.
What margin does Lean FIRE leave?
Very little, by construction. A portfolio sized to a spending floor has no discretionary spending left to cut when markets fall, which is exactly when cutting withdrawals matters most. That is the structural weakness of the approach.
The common mitigations are keeping some earning capacity available, holding a larger cash buffer for the first years, or sizing to a slightly lower withdrawal rate so the floor sits below what the portfolio could actually support.
Your Privacy is Protected
All calculations run entirely in your browser. We never collect, store, or transmit any data you enter into this calculator. There are no APIs, no server requests, and no logs - your financial information stays on your device and disappears when you close the page.
For informational and educational purposes only — not investment advice.