Rule of 72 Calculator: Years to Double Your Money
Use the rule of 72 to see how many years it takes to double your money at a given return, or the rate you need, compared with the exact result.
The rule of 72 is closest between 6% and 10%. For low rates the rule of 70 (or 69.3) is closer; the exact value is ln 2 ÷ ln(1 + rate).
| Return | Rule of 72 | Exact |
|---|
What it does
The rule of 72 is a quick way to estimate how long an investment takes to double with compound interest: divide 72 by the yearly return in percent. It also works backwards, dividing 72 by the years to find the rate you need, and for inflation, which halves the value of money in 72 ÷ inflation years. The calculator shows the estimate next to the exact value.
How to use it
- Choose whether you know the yearly return or the years to double.
- Type the value.
- See the rule of 72 result, the exact value, the rules of 70 and 69.3 and the years to triple and quadruple.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How long does it take to double money at 8%?
72 ÷ 8 = 9 years by the rule of 72. The exact value is 9.006 years, so the rule is almost perfect here.
What return do I need to double my money in 10 years?
72 ÷ 10 = 7.2% a year by the rule. The exact rate is 7.18%.
Why 72?
The exact doubling time is ln 2 ÷ ln(1 + r), about 69.3 ÷ rate for small rates. 72 is a little higher, which fits typical rates better, and it divides easily by 2, 3, 4, 6, 8, 9 and 12.
π Compound Interest Calculator
π CAGR Calculator
π₯ FIRE Calculator: Financial Independence, Retire Early
β© Future Value Calculator