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Rule of 72 Calculator

Estimate how long money takes to double and compare the Rule of 72 shortcut with an exact compounded calculation.

Your inputs

Investments
YOUR RESULT

Approximate doubling time

9

Headline is in years. Compare it with the exact annual-compounding result.

Exact doubling years
9.0065
Difference in years
-0.0065
Annual rate
8%
Calculation method & assumptions

The shortcut uses 72 / annual percentage return. The exact comparison uses ln(2) / ln(1 + rate / 100).

The Rule of 72 is an approximation. Both figures assume an unchanged annual compounded rate.

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HOW IT WORKS

Three steps. Ready for what’s next.

01

Enter your inputs

Use the labelled fields and select the assumptions or dates that apply to your calculation.

02

Review the result

Results update as inputs change. Check the breakdown, calculation method and assumptions.

03

Copy or download

Copy a summary or download the calculation breakdown as a CSV.

About Rule of 72 Calculator.

How rule of 72 is calculated

The shortcut uses 72 / annual percentage return. The exact comparison uses ln(2) / ln(1 + rate / 100).

What the result means

Estimate how long money takes to double and compare the Rule of 72 shortcut with an exact compounded calculation.

Assumptions and scope

The Rule of 72 is an approximation. Both figures assume an unchanged annual compounded rate.

Using the calculator

Enter annual compounded return. Change the values to compare results. Calculations run in your browser. No account is required.

A LITTLE CLARITY

Good questions. Simple answers.

A few helpful answers before you get started.

Do I need an account?

No. This tool is open to everyone without signing in.

Does this tool need the internet?

Your inputs are calculated in this browser. Load the tool online before using it offline.

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