Rule of 72 Calculator

How it's calculated

Years to double ≈ 72 ÷ annual return %. The exact figure is ln 2 ÷ ln(1 + r). The shortcut is most accurate between 6% and 10%.

What the Rule of 72 tells you

The Rule of 72 is a quick way to estimate how long it takes an investment to double. Divide 72 by the annual return as a percentage and you get the approximate number of years. It works because of how compound growth behaves, and it needs no calculator.

At a 9% annual return, 72 ÷ 9 gives 8 years. The exact figure is about 8.04 years, so the shortcut is very close. It is most accurate for returns of roughly 6% to 10%. The calculator also shows the Rule of 114 for tripling and the Rule of 144 for growing four times.

Frequently asked questions

How do I use the Rule of 72?

Divide 72 by your expected yearly return. At 12%, 72 ÷ 12 gives about 6 years to double.

How accurate is the Rule of 72?

It is a close estimate for returns of about 6% to 10% and less exact outside that range. The calculator also shows the exact figure.

Can I use it for inflation?

Yes. At 6% inflation, prices double in about 12 years, so money loses half its buying power in that time.

How to use the Rule of 72 Calculator

Enter annual return. The calculator updates as you type and shows Years to double (Rule of 72), along with the figures behind it. It runs in your browser, so nothing you enter is sent anywhere. Use the Reset button to go back to the example values.