The Rule of 72

A mental-maths trick for compound growth.

Take 72. Divide by the yearly rate.

The answer is about how many years it takes to double.

72 ÷ 6 = 12 years, for example.

€1,000 becomes about €2,000.

It is an estimate. Real returns change from year to year.

What rate could you try it with?

Education, not investment advice.

Read the sheet as text

The Rule of 72.
How many years for your money to double? Divide 72 by the yearly rate.

Years to double, for example:
3% a year: 72 ÷ 3 = 24 years.
6% a year: 72 ÷ 6 = 12 years.
9% a year: 72 ÷ 9 = 8 years.
12% a year: 72 ÷ 12 = 6 years.

For example: €1,000 becomes about €2,000 in about 12 years at 6% a year.
A quick estimate, close for rates up to about 10%. Example rates, not a forecast.

Sources (1)

Doubling Your Money With the "Rule of 72"Nebraska Department of Banking and Finance (a US state regulator), undated: divide 72 by the expected annual return to get the years to double. A US page, used only for the plain description of the rule. Checked 2026-10-29.