Rule of 72 Calculator
Estimate how long it takes to double, triple, or quadruple your money based on your expected rate of return.
Double (Rule of 72)
Triple (Rule of 114)
Quadruple (Rule of 144)
How it works
The Rule of 72 states that you can divide the number 72 by your annual rate of return to estimate how many years it will take to double your investment. For example, at an 8% return, 72 / 8 = 9 years.
The exact formula to find the time to reach a multiple `M` is `ln(M) / ln(1 + r)`. The rules of thumb (72, 114, 144) are just easy mental shortcuts for this math.
Frequently Asked Questions
The Rule of 72 is a quick, useful formula that is popularly used to estimate the number of years required to double the invested money at a given annual rate of return.
It is a fairly accurate estimate for interest rates between 6% and 10%. For very high or very low rates, the actual time to double will vary slightly from the Rule of 72 estimate, which is why we also show the exact compound interest calculation.
Just as dividing 72 by the interest rate estimates the time to double your money, dividing 114 by the rate estimates the time to triple it, and dividing 144 by the rate estimates the time to quadruple it.