Rule of 72 Calculator
Enter an annual interest or return rate to quickly estimate how long it will take your money to double.
Rule of 72 Calculator
Estimates how many years it takes an investment to double at a given annual rate of return, using the Rule of 72.
The Rule of 72 is a quick mental-math shortcut for estimating doubling time: divide 72 by the annual percentage rate to get approximately how many years it takes an investment (or a debt, if you're thinking about it that way) to double in value. This calculator does that division precisely so you don't have to do it in your head, and it's a handy way to intuitively compare the long-run power of different return rates without running a full compound-interest projection.
Example
- With the default values shown above, this calculator returns: Years to Double ≈ 9.
Frequently Asked Questions
How accurate is the Rule of 72?
It's a well-known mental-math approximation that's quite accurate for annual rates roughly between 6% and 10%, and gets slightly less precise the further the rate is from that range.
Does it work for other multiples, like tripling?
The Rule of 72 is specifically for doubling; tripling time is often estimated with a similar 'Rule of 114', but this calculator is dedicated to the doubling case.
Sources
- Standard formula, publicly documented method