FIRE Number Calculator — Financial Independence Retire Early
Enter your annual expenses, current savings, annual savings rate, expected investment return, and preferred withdrawal rate to calculate your personal FIRE number. The tool computes your standard FIRE, Lean FIRE (75% spending), and Fat FIRE (150% spending) targets, then estimates how many years until you reach financial independence based on compound growth.
Your FIRE Number
$1,000,000
Years to FIRE
18 years
Lean FIRE
$750,000
Fat FIRE
$1,500,000
Based on $40,000/year at 4% withdrawal rate
How it works
What is the FIRE number?
The FIRE number is the total investment portfolio size you need to cover your living expenses indefinitely without working. It is calculated by dividing your annual expenses by your withdrawal rate. Using the classic 4% rule, the formula becomes: FIRE number = annual expenses × 25. For example, if you spend $40,000 per year, you need $1,000,000 invested.
The 4% rule originates from the Trinity Study (1998), which analyzed historical US stock and bond returns. It found that a 60/40 portfolio could sustain a 4% annual withdrawal for at least 30 years in 95% of historical scenarios. Many modern FIRE planners use 3–3.5% to account for longer retirement horizons (40–60 years) and more conservative market expectations.
Lean FIRE vs Fat FIRE
FIRE has evolved into several variants based on lifestyle goals. Lean FIRE targets minimal spending — typically 75% or less of the median income — and requires a smaller nest egg but demands frugal living. It suits people who can live comfortably on reduced expenses and have no dependents. The Lean FIRE number is roughly 18.75× annual expenses at a 4% withdrawal rate.
Fat FIRE, by contrast, targets a comfortable or even luxurious retirement with 150% or more of typical expenses. It requires a much larger portfolio but provides a wide margin of safety and room for healthcare costs, travel, and unexpected spending. Barista FIRE (part-time work covering some expenses) and Coast FIRE (stop saving but let existing investments compound) are additional variants for those who want flexibility before reaching full FIRE.
Compound growth and the years-to-FIRE estimate
This calculator estimates years to FIRE by simulating annual portfolio growth: balance = balance × (1 + return rate) + annual savings. This compound model shows why early career savings matter so much — money invested early has more years to compound. The difference between a 6% and 7% return rate can shift your FIRE date by several years on a large portfolio.
Your FIRE date depends heavily on your savings rate, not just your income. Someone earning $100,000 and saving 50% ($50,000/year) will typically reach FIRE faster than someone earning $200,000 but saving only 10% ($20,000/year), because the high saver has both a smaller target (lower expenses) and a faster fill rate. Track your savings rate as a percentage of take-home pay for the clearest signal.
Frequently asked questions
›What is the 4% rule?
The 4% rule states that you can safely withdraw 4% of your portfolio in the first year of retirement, then adjust for inflation each year, without running out of money over a 30-year period. It comes from the 1998 Trinity Study, which analyzed US market returns from 1926 to 1995. Many FIRE practitioners treat it as a starting point rather than a guarantee.
›How is the FIRE number calculated?
FIRE number = annual expenses ÷ withdrawal rate. At the classic 4% withdrawal rate, this equals annual expenses × 25. If you spend $50,000/year, your FIRE number is $1,250,000. At a more conservative 3.5% rate, the same expenses require $1,428,571.
›What is Lean FIRE?
Lean FIRE means retiring with a minimal lifestyle, typically spending well below the median income. The Lean FIRE target in this calculator uses 75% of your entered annual expenses, implying you could cut back before or during retirement. It suits people comfortable with frugal living and who have low fixed costs.
›What is Fat FIRE?
Fat FIRE means retiring with enough wealth to maintain a comfortable or generous lifestyle — typically 1.5× your current spending or more. The Fat FIRE target here uses 150% of your entered annual expenses. It offers a larger safety margin for healthcare, travel, and lifestyle inflation.
›Should I include Social Security in my FIRE calculation?
If you retire before Social Security eligibility (62–70 in the US), you should not include it in your FIRE number calculation for the early years. Once you reach eligibility, Social Security can reduce the amount you need to withdraw from your portfolio, effectively lowering your required FIRE number. Run the calculation both ways to understand your full range.
›What return rate should I use?
Historical US stock market returns have averaged 7–10% nominally (4–7% after inflation). A common conservative estimate for a diversified portfolio is 6–7% nominal. Many FIRE planners use 5–6% to account for sequence-of-returns risk and lower future expected returns. Do not use more than 8% unless you have a reason specific to your portfolio.
›Does the calculator account for inflation?
This calculator uses nominal (not inflation-adjusted) returns. To approximate inflation-adjusted projections, reduce your expected return by 2–3 percentage points (subtract an assumed inflation rate). For example, if you expect 7% nominal returns and 2.5% inflation, use 4.5% in the return field. Your expenses figure should be in today's dollars.
›What is Barista FIRE?
Barista FIRE is a hybrid approach where you retire from your main career but take a part-time job that covers current living expenses (and sometimes healthcare). This lets your existing investments grow untouched, reaching full FIRE faster than if you were withdrawing from them. The name comes from the idea of working a low-stress job (like a coffee shop) for benefits and supplemental income.
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