FIRE Calculator
FIRE — Financial Independence, Retire Early — boils down to one number: 25 times your annual spending. This calculator finds yours, projects your savings with compound growth, and tells you exactly how much to save each year to close any gap.
What is the FIRE number?
Your FIRE number is 25× your annual spending. Reach it, and work becomes optional.
The 25 comes from the 4% rule, born in the 1994 Trinity Study. Researchers found that a stock-and-bond portfolio historically survived 30-year retirements when you withdraw 4% in year one and adjust for inflation after. Flip the fraction (1 ÷ 0.04) and you get 25.
Spend $50,000 a year and your number is $1,250,000. Spend $40,000 and it's a clean $1,000,000. Notice what moves the needle: spending gets multiplied by 25, so it's the most powerful lever you have. Not your salary. Not your returns. Your spending.
How this calculator works
It grows two things with compound interest: your current savings, untouched, and each year's contribution for the years remaining until your target age. Then it compares the projection with your FIRE number.
Fall short and it works backwards, solving for the annual savings that would close the gap. That's your target number. No guesswork.
Formula
Example
Age 30. Retire at 50. Spend $50,000 a year. Already saved $50,000. Adding $20,000 a year. Assuming 7% returns.
FIRE number: $1,250,000. Projected savings after 20 years: about $1,013,000. Shortfall: $237,000. To erase it, yearly savings need to rise to roughly $25,800.
Here's the part people miss: that extra $5,800 a year, invested for 20 years at 7%, grows into more than $237,000. Small increases, started early, do absurd amounts of work.
The savings rate secret
Here's the counterintuitive bit: your savings rate predicts your retirement date better than your income does. The famous table from Mr. Money Mustache's "Shockingly Simple Math" puts numbers on it. Save 50% of your income and you're looking at roughly 17 working years. Save 65% and it's about 10.5. That holds whether you earn $60,000 or $200,000.
Translation: a high earner who spends everything retires never. A modest earner who banks half the paycheck can be done in under two decades.
Variants of FIRE
- Lean FIRE — fully retired on a minimalist budget, often under $40k a year.
- Fat FIRE — retired comfortably, $100k+ a year in spending.
- Coast FIRE — save enough early that compounding finishes the job, then keep working to cover the bills. Run your Coast FIRE number.
- Barista FIRE — leave the career, pick up part-time work for fun and benefits. See the Barista FIRE math.
Withdrawal strategies in early retirement
Reaching your number is half the job. Spending it safely for 50-plus years is the other half. The default is the 4% rule with yearly inflation bumps, but early retirees usually add armor:
- Guardrails. Withdraw 4%, but trim spending 10% after a bad market year and raise it 10% after a great one. Research, notably by Kitces, shows this simple rule massively improves portfolio survival.
- Bond tent. Hold extra bonds for roughly five years before and after retiring to cushion early crashes, then drift back toward stocks.
- Dynamic withdrawals. Base each year's withdrawal on how the portfolio actually performed, instead of a fixed inflation-adjusted amount. The VPW method is the best-known version.
- Income floor. Cover must-pay bills with predictable income: rent, part-time work, Social Security later. Market swings then only touch the fun money.
Most early retirees who make it combine at least two of these. The calculator gives you the target. These protect it.
Limitations
The 4% rule was built for 30-year retirements. Retiring at 40 means funding 50-plus years, so many planners use 3.5% instead. That's 28.6× spending, a noticeably bigger target.
It also leans on US market history. Retiring elsewhere? Use more conservative numbers. And it says nothing about health insurance before Medicare, which blindsides plenty of early retirees. Treat this calculator as a planning tool, not a promise.