Rule of 72 Formula: To use the rule of 72, divide the interest rate of your investment by 72 to determine the approximate number of years it will take for your investment to double.

Rule of 72 Definition The free online Rule of 72 Calculator is a really nifty financial calculator that uses the rule of 72 formula for determining how many years it will take for your investment to double. The Rule of 72 is an easy way to find out the approximate amount of time that it will take for your current invested amount to double. Try out the free Rule of 72 Calculator and then be sure and use all of our other free calculators!

How to Calculate Rule of 72 Let's be honest - sometimes the best rule of 72 calculator is the one that is easy to use and doesn't require us to even know what the rule of 72 formula is in the first place! But if you want to know the exact formula for calculating rule of 72 then please check out the "Formula" box above.