Rule of 72 Calculator
Updated on 22 Oct 2026 · Checked by Aotob
At 7% a year your money doubles in about 10.3 years.
The exact answer is 10.24 years. The rule is most accurate between 6% and 10%.
Years to double
10.3years
It works the other way too: at 3% inflation, prices double in about 24 years.
Show the working
72 ÷ 7 = 10.29
Exact: ln 2 ÷ ln(1 + 7%) = 10.24
Doubling time by rate
| Rate | Rule of 72 | Exact |
|---|---|---|
| 1% | 72 | 69.7 |
| 2% | 36 | 35 |
| 3% | 24 | 23.4 |
| 4% | 18 | 17.7 |
| 5% | 14.4 | 14.2 |
| 6% | 12 | 11.9 |
| 8% | 9 | 9 |
| 10% | 7.2 | 7.3 |
| 12% | 6 | 6.1 |
Questions people ask
What is the rule of 72?
Divide 72 by the yearly return to get the years it takes to double. At 8%, about 9 years. It is a quick mental shortcut.
How accurate is it?
Within a few months between about 4% and 12%, and closest from 6% to 10%. At low rates 69 or 70 is closer, and at high rates 76 or 78.
Does it work for inflation?
Yes. At 3% inflation prices double, and money’s value halves, in about 24 years.
Updated 22 Oct 2026Source: Standard financial maths (time value of money)Checked by AotobNot financial advice.Report an issue