FIRE Calculator
Work out how much you need to retire early, how many years it will take at your savings rate, and your Coast FIRE number, with a year-by-year projection.
Portfolio growth toward your FIRE number
Year-by-year table
| Year | Age | Contribution | Growth | End balance | % of target |
|---|
Contributions are added at the end of each year and returns are compounded yearly. Use a real (inflation-adjusted) return so every figure stays in today's money.
How to use the FIRE Calculator
- Enter your yearly spending in retirement, or tap Lean, Regular or Fat FIRE for a quick preset.
- Add what you have invested today, your take-home income and the percentage of it you save.
- Set the expected real return (after inflation) and your safe withdrawal rate, 4% by default.
- Enter your age and a traditional retirement age to see your Coast FIRE number.
- Press Calculate and read your FIRE number, years to FI, chart and year-by-year table. Export it as CSV if you like.
The FIRE formulas
The calculator uses three simple formulas. All money values are in today's money when you enter a real (after-inflation) return.
- FIRE number = annual expenses ÷ safe withdrawal rate. At 4% that is 25 × expenses; at 3.5% it is about 28.6 ×.
- Portfolio after n years = S × (1 + r)n + C × ((1 + r)n − 1) ÷ r, where S is current savings, C the yearly contribution and r the return.
- Years to FI = ln((T + C/r) ÷ (S + C/r)) ÷ ln(1 + r), where T is the FIRE number.
- Coast FIRE number = T ÷ (1 + r)years until retirement age.
Worked example
Suppose you spend 40,000 a year, have 100,000 invested, earn 100,000 after tax and save 60% of it (60,000 a year), with a 7% real return and the 4% rule.
- FIRE number: 40,000 ÷ 0.04 = 1,000,000.
- C ÷ r = 60,000 ÷ 0.07 ≈ 857,143.
- Years to FI = ln(1,857,143 ÷ 957,143) ÷ ln(1.07) ≈ 9.8 years.
- Coast FIRE at age 30 with retirement at 65: 1,000,000 ÷ 1.0735 ≈ 93,663, so this saver has already reached Coast FIRE.
Savings rate vs. years to financial independence
Starting from zero, with a 5% real return and the 4% rule, and assuming you spend everything you do not save:
| Savings rate | Years to FI | Savings rate | Years to FI |
|---|---|---|---|
| 10% | 51.4 | 50% | 16.6 |
| 20% | 36.7 | 60% | 12.4 |
| 30% | 28.0 | 70% | 8.8 |
| 40% | 21.6 | 80% | 5.6 |
The time to FI depends only on your savings rate, not your income, because a higher rate both builds the portfolio faster and lowers the spending it has to support.
Frequently asked questions
What is a FIRE number?
Your FIRE number is the size of the investment portfolio you need to live off it indefinitely. With the 4% rule it is your annual expenses multiplied by 25, so spending 40,000 a year needs a 1,000,000 portfolio.
What is the 4% rule?
The 4% rule says you can withdraw about 4% of your portfolio in the first year of retirement and adjust that amount for inflation each year with a low chance of running out of money over 30 years. It comes from historical US stock and bond returns, so many early retirees with longer horizons use 3.25% to 3.75% to be more conservative.
What is Coast FIRE?
Coast FIRE means you have invested enough that, without adding another penny, compound growth will carry your portfolio to your full FIRE number by a normal retirement age. The Coast FIRE number is your FIRE number divided by (1 + return) raised to the years left until that age.
What is the difference between Lean, Regular and Fat FIRE?
They describe the lifestyle your portfolio funds. Lean FIRE is a frugal budget (often around 40,000 a year or less), Regular FIRE is a typical middle-class budget, and Fat FIRE is a comfortable budget of roughly 100,000 a year or more, which needs a much bigger portfolio.
Should I use a real or nominal return?
Use a real return, meaning the expected return minus inflation. Long-run stock market returns of about 10% nominal are roughly 7% real. With a real return every number in the calculator is in today's money, so your expenses do not need to be inflated.
Why does my savings rate matter so much?
A higher savings rate both adds more money each year and usually means you spend less, which lowers the FIRE number you need. That is why moving from a 20% to a 50% savings rate can cut the time to FI from about 37 years to about 17 years.
Is this calculator financial advice?
No. It is an educational projection that assumes a constant return, steady contributions and no taxes on withdrawals. Real markets vary year to year, so revisit your plan regularly and consider professional advice for big decisions.