Rule of 72 Calculator

Quickly estimate how many years it takes for money to double, triple or quadruple — or the return needed to double in a given time.

What is the Rule of 72 Calculator?

The Rule of 72 is a mental-math shortcut: divide 72 by the annual return to estimate the years to double your money.

How does it work?

The calculator shows the Rule of 72 estimate alongside the exact answer using logarithms, plus the Rule of 114 (triple) and Rule of 144 (quadruple).

Formula

Years to double ≈ 72 ÷ rate
Exact = ln(2) ÷ ln(1 + rate)

Example

At 8% a year, money doubles in about 72 ÷ 8 = 9 years (exactly 9.01 years).

Frequently asked questions

How accurate is the Rule of 72?

It is very accurate for rates between 6% and 10%. For much higher or lower rates, rely on the exact figure.

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