The Rule of 72 is a way to estimate how long it will take for an investment to double at a given interest rate, assuming a fixed annual rate of interest. You simply take 72 and divide it by the interest rate number. So, if the interest rate is 6%, you would divide 72 by 6 to get 12. This means that the investment will take about 12 years to double with a 6% fixed annual interest rate.

This calculator flips the 72 rule and shows what interest rate you would need to double your investment in a set number of years. Enter the number of years you'd like an investment to double and see what the interest rate would be to make it happen.

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