Rule of 72 Calculator
Estimate how long it takes money to double.
Rule of 72
10.3
years to double
Exact (compound)
10.2
years to double
Difference: 0.04 years. The Rule of 72 stays within a year of exact between roughly 4% and 12%.
Common rates
- 2% (cash): doubles in 36 years
- 5% (bonds): doubles in 14 years
- 7% (stocks, real return): doubles in 10 years
- 10% (stocks, nominal): doubles in 7.2 years
About
Divide 72 by your interest rate and you get the years it takes for a sum to double. The tool also runs the math the other way (years to required rate) and shows the actual number using compound interest, since rule-of-72 is an approximation.
How to use
- Enter an interest rate.
- See doubling time via Rule of 72 and exact compounding.
FAQ
How accurate is Rule of 72?+
Very close for rates between 6% and 10%. Drifts a few percent off at extreme rates. The tool shows the exact answer alongside for comparison.