How does the Rule of 72 Calculator work?

Years to double = 72 / Annual Interest Rate (%) Then: Rate needed to double = 72 / Number of years Then: Works best for rates between 6% and 10% (±1 year accuracy) Then: For continuous compounding, use 69.3 instead of 72.

Can you give an example of how to use the Rule of 72 Calculator?

Example: Input 8% annual return gives a result of Doubles in ~9 years (72/8) (Actual: 9.01 years).

Is the Rule of 72 Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Rule of 72 Calculator?

Our Rule of 72 Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

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Rule of 72 Calculator

Rule of 72

Estimate how many years it takes to double an investment.

Annual Return Rate

The Rule of 72 is a simple mental math shortcut to estimate how long it takes an investment to double, or what growth rate is needed to double in a given time. Divide 72 by the annual return rate to get years to double.

Annual Rate	Years to Double	Actual Years
2%	36 years	35.0
3%	24 years	23.4
6%	12 years	11.9
8%	9 years	9.0
10%	7.2 years	7.3
12%	6 years	6.1
18%	4 years	4.2
72%	1 year	1.3

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Pro Tip

Use Rule of 115 to estimate tripling time: 115 / rate. Use Rule of 144 for quadrupling: 144 / rate.

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Did You Know?

The Rule of 72 also works in reverse for debt. At 18% credit card interest, your debt doubles in just 4 years if you make no payments. At 24% payday loan rates, it doubles in 3 years.

References

›Rule of 72 — Wikipedia

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