What is Lean FIRE?
Lean FIRE means saving enough to stop working, then living on a smaller budget than most retirees. There's no official cutoff. Boldin calls $25,000 to $30,000 a year lean, and ProjectionLab puts it under $40,000 a year for one person. Your Lean FIRE number is that budget divided by your withdrawal rate.
How the calculator works
Pick one of the budget buttons or type your own yearly spending, in today's dollars. The calculator divides it by your withdrawal rate to get the amount you need invested on the day you quit. It's the same engine as our other calculators. Only the starting budget and the advice on this page are different.
Lean FIRE number = yearly spending ÷ withdrawal rateA $30,000 budget at 4% needs $750,000. At 3.5% the same budget needs about 28.6 times its yearly spending.
Because the budget is small, every dollar counts for more. At 4%, each $1,000 you trim from your yearly spending lowers your number by $25,000. That's the appeal of Lean FIRE: cutting spending works on both sides at once. You need less saved, and you save more each year while you get there.
Why lean plans often use a lower withdrawal rate
People who go lean usually do it to retire early, and an early retirement is a long one. The 4% rule comes from studies of 30-year retirements. If you quit at 40, your money may have to last 55 years. A lean budget also leaves little to cut when markets fall, since most of it is rent, food, insurance and other basics. Both point the same way. Many lean planners use 3.5% or less, and the table under your result shows what that costs.
If you'll get Social Security or a pension later, add it. Even a modest benefit that starts at 67 takes real pressure off a small budget, and the calculator accounts for the years before it starts.
Three worked examples
Example 1: a single person on $30,000
A single renter in a low-cost city lives on $30,000 a year and plans to keep that budget in retirement. They use a 4% withdrawal rate.
| Spending per year | $30,000 |
|---|---|
| Withdrawal rate | 4% |
| Lean FIRE number | $750,000 |
|---|
$750,000 is a lot of money, but it's half of what someone spending twice as much would need. That gap is why lean budgets reach financial independence years sooner on the same income.
Example 2: retiring at 40
A 30-year-old wants to stop working at 40 on $35,000 a year. Since the money has to last from 40 to 95, they plan around a 3.5% withdrawal rate.
| Retire at | 40 |
|---|---|
| Spending per year | $35,000 |
| Withdrawal rate | 3.5% |
| Lean FIRE number | $1,000,000 |
|---|
A 3.5% rate means 28.6 times spending instead of 25, so $1,000,000 rather than what the classic rule would give. The extra cushion matters most in the first ten years, when a market crash does the most damage to a long retirement.
Example 3: a couple counting Social Security
A couple plans to retire at 45 on $40,000 a year between them. They expect $20,000 a year of Social Security between them from 67, after tax and in today's dollars.
| Spending per year | $40,000 |
|---|---|
| Retire at | 45 |
| Social Security | $20,000 a year from 67 |
| Withdrawal rate | 4% |
| Lean FIRE number | $817,490 |
|---|---|
| Without Social Security | $1,000,000 |
Social Security covers half their budget from 67, which brings the number down to $817,490 from $1,000,000. It doesn't go lower because their savings pay the full $40,000 for the 22 years before the checks start.
Lean FIRE vs Coast FIRE vs Barista FIRE
These get mixed up because they can all lead to leaving full-time work early. They're different deals:
- Lean FIRE: you stop working completely and live on a small budget from your savings. You need your whole FIRE number, just a smaller one.
- Coast FIRE: you stop saving for retirement, but keep working enough to pay your bills. Your investments grow into your full number on their own. What is Coast FIRE? explains it, and the Coast FIRE calculator finds the age you could stop saving.
- Barista FIRE: you leave full-time work and take a part-time job that covers part of your spending, often including health insurance. Your savings fill the rest. The Barista FIRE calculator works out how much you need first.
You can combine them. A common plan is to reach your Coast number early, keep a job you like, and decide later whether a lean early retirement or a little part-time work suits you better.
Why Lean FIRE numbers vary so much
- The definition. Some sources talk about a household budget, others about one person. A lean budget for a family of four is a lot more than for one person in a small apartment.
- The withdrawal rate. Lean plans are usually early retirements, so some tools default to 3.5% or 3.25% instead of 4%, which raises the number by 14% or more.
- Health insurance. In the US, coverage before Medicare at 65 can take a big share of a lean budget. Some calculators include it, many don't.
- Where you live. The same lifestyle can cost very different amounts in different places, which is why the budget buttons are only starting points.
What this calculator doesn't do
- It doesn't price health insurance separately. Put your expected premiums and out-of-pocket costs into your yearly spending, or use the Barista FIRE calculator, which has a separate field for coverage before 65.
- It doesn't model subsidies or benefits that depend on income, such as ACA premium credits. A low income in early retirement can make those worth a lot.
- It assumes your spending stays flat in real terms. Lean budgets tend to have less room to absorb surprises like a new roof or a big medical bill, so many people keep a separate cash buffer.
- It uses one flat tax rate. On a lean budget your tax rate may be very low, especially in the years before Social Security.
Common questions
What is Lean FIRE?
It's financial independence on a small budget: enough invested to stop working, with a lifestyle that costs less than most retirees spend. It appeals to people who'd rather retire years earlier than keep working to afford more.
How much do you need for Lean FIRE?
At a 4% withdrawal rate, 25 times your yearly spending. A $25,000 budget needs $625,000 and a $40,000 budget needs $1,000,000. If you plan to retire before about 55, a 3.5% rate is safer, which means about 28.6 times your spending.
Is $500,000 enough for Lean FIRE?
At 4%, $500,000 supports $20,000 a year. That can work for one person in a low-cost area, especially with Social Security coming later, but it leaves very little slack. Enter your own budget and benefits above to see where you stand.
What's the difference between Lean FIRE and Coast FIRE?
With Lean FIRE you stop working and live on your savings. With Coast FIRE you stop saving but keep earning enough to cover your bills while your investments grow. Coast FIRE needs much less saved today; Lean FIRE gets you out of work entirely.
Is Lean FIRE risky?
It's riskier than a bigger budget in one way: there's less you can cut when markets fall or costs rise. Using a lower withdrawal rate, keeping some cash on hand and being open to occasional part-time income all reduce that risk.
Can a couple do Lean FIRE?
Yes. Enter your combined yearly spending and both Social Security benefits added together. For separate retirement ages or benefits that start at different times, use the Coast FIRE calculator and add a partner.
Sources
- Boldin. FIRE Retirement Calculator: How can I retire early? www.boldin.com/retirement/fire-calculator
- ProjectionLab. What is Lean FIRE? projectionlab.com/financial-terms/lean-fire
- Cooley, Philip L., Carl M. Hubbard and Daniel T. Walz. "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal, February 1998. Usually called the Trinity study.
- Jeske, Karsten (Early Retirement Now). The Safe Withdrawal Rate Series. earlyretirementnow.com/safe-withdrawal-rate-series
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