FIRE number formula
FIRE number = Annual spending ÷ Safe withdrawal rate
The time to reach it assumes your savings grow at the expected real return with monthly compounding and that you add your annual savings evenly through the year.
Example: You spend $50,000 a year and use a 4% withdrawal rate: your FIRE number is $1,250,000. Starting with $50,000, saving $20,000 a year at a 5% real return, you reach it in about 26 years. Lean FIRE (70% of spending) would need $875,000; Fat FIRE (150%) $1,875,000.
Ways to reach FIRE faster
- Savings rate matters most. Cutting spending lowers the target and raises savings at the same time.
- Use tax-advantaged accounts — 401(k), IRA, HSA — to keep more of your returns.
- Keep fees low. A 1% fund fee can delay financial independence by years.
- Plan for health insurance before Medicare age if you retire early.
Already have a good balance? The Coast FIRE calculator shows whether you could stop saving and let compounding finish the job.
Frequently asked questions
How do I calculate my FIRE number?
Divide your expected annual spending in retirement by your safe withdrawal rate. At 4%, that is 25 times spending: $50,000 a year × 25 = $1,250,000. At 3.5% it is about 28.6 times.
Is the 4% rule still safe?
The 4% rule comes from studies of U.S. stock and bond returns over 30-year retirements. For early retirees with 40–50 year horizons, many planners prefer 3.25–3.75%. The calculator lets you choose.
What are Lean FIRE and Fat FIRE?
Lean FIRE is financial independence on a frugal budget; Fat FIRE supports a more comfortable lifestyle. The calculator shows both at 70% and 150% of your spending.
Do I include Social Security or pensions?
Subtract any guaranteed income you expect from your annual spending before calculating. If a pension will pay $15,000 of your $50,000, your portfolio only needs to cover $35,000.