Compound Interest Rule of 72

Problem

Calculating how long it takes for investment to double requires complex formulas.

Solution

Divide 72 by the interest rate to get approximate years to double.

Benefit

Quick investment doubling time calculation without formulas or calculators.

Example

6% annual return:
72 ÷ 6 = 12 years to double

9% annual return:
72 ÷ 9 = 8 years to double

12% annual return:
72 ÷ 12 = 6 years to double