FIRE Number Calculator
If you draw a fixed share of the portfolio each year, the portfolio you need is yearly spending divided by that share. Spending 36,000,000 a year at 4% needs 900,000,000 — twenty-five times the spending. The 4% figure comes from William Bengen in 1994, who tested thirty-year withdrawals against historical US stock and bond returns; the Trinity study then popularised it. It is one study, on one market, over one thirty-year horizon — not a law.
Your numbers
Portfolio needed
900,000,000
Multiple
25×
Monthly spend
3,000,000
Formula
Portfolio needed = Yearly spending ÷ (Withdrawal rate ÷ 100)
A lower withdrawal rate raises the target sharply: 4% is 25×, 3% is 33.3×, 2% is 50×. Leave tax, health insurance and large repairs out of your yearly spending and the target comes out too small.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Yearly spendingEverything you spend in a year; include tax and insurance or the target is too low. | 36,000,000 | 0 and up |
| Withdrawal rate (%)The share you draw from the portfolio each year; lower means a bigger portfolio. | 4 | 0 ~ 20 |
Step by step
Quick reference table
Results when only Yearly spending changes and everything else stays put.
| Yearly spending | Portfolio needed | Multiple (×) | Monthly spend |
|---|---|---|---|
| 18,000,000 | 450,000,000 | 25 | 1,500,000 |
| 27,000,000 | 675,000,000 | 25 | 2,250,000 |
| 36,000,000 | 900,000,000 | 25 | 3,000,000 |
| 54,000,000 | 1,350,000,000 | 25 | 4,500,000 |
| 72,000,000 | 1,800,000,000 | 25 | 6,000,000 |
What each result means
| Result | At default values |
|---|---|
| Portfolio neededThe portfolio that carries that spending at that withdrawal rate. | 900,000,000 |
| Multiple (×)How many times over; doubling is a 100% increase. | 25 |
| Monthly spendWhat you spend in a month, fixed and variable together. | 3,000,000 |
Common mistakes
A lower withdrawal rate raises the target sharply: 4% is 25×, 3% is 33.3×, 2% is 50×. Leave tax, health insurance and large repairs out of your yearly spending and the target comes out too small.
Glossary
- Yearly spending
- Everything you spend in a year; include tax and insurance or the target is too low.
- Withdrawal rate
- The share you draw from the portfolio each year; lower means a bigger portfolio.
- Portfolio needed
- The portfolio that carries that spending at that withdrawal rate.
- Multiple
- How many times over; doubling is a 100% increase.
- Monthly spend
- What you spend in a month, fixed and variable together.
Frequently asked questions
Q. How is FIRE Number Calculator calculated?
Portfolio needed = Yearly spending ÷ (Withdrawal rate ÷ 100) — If you draw a fixed share of the portfolio each year, the portfolio you need is yearly spending divided by that share. Spending 36,000,000 a year at 4% needs 900,000,000 — twenty-five times the spending. The 4% figure comes from William Bengen in 1994, who tested thirty-year withdrawals against historical US stock and bond returns; the Trinity study then popularised it. It is one study, on one market, over one thirty-year horizon — not a law.
Q. Can you walk through an example?
With Yearly spending 36,000,000, Withdrawal rate 4%, the answer is Portfolio needed 900,000,000.
Q. What do I need to enter?
Enter Yearly spending, Withdrawal rate. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Yearly spending moves the answer to Yearly spending 18,000,000 → Portfolio needed 450,000,000 and Yearly spending 72,000,000 → Portfolio needed 1,800,000,000. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
A lower withdrawal rate raises the target sharply: 4% is 25×, 3% is 33.3×, 2% is 50×. Leave tax, health insurance and large repairs out of your yearly spending and the target comes out too small.
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Tax rates and interest conventions differ by country and product — check your contract for real transactions.