Question 1

What is the Rule of 72?

Accepted Answer

The Rule of 72 is a simple formula for estimating how long it takes savings or investments to double in value. Divide 72 by the annual rate of return to get the approximate number of years.

Question 2

How accurate is the Rule of 72?

Accepted Answer

The Rule of 72 is an approximation, but it is very accurate for rates between 6% and 10%. For lower or higher rates, the exact compound interest formula gives more precise results.

Question 3

Can this calculator show exact results?

Accepted Answer

Yes. This calculator shows both the Rule of 72 shortcut estimate and the exact result using the compound interest formula, so you can compare quick mental maths with precise calculations.