Rule of 72 Calculator

Enter a yearly return to see roughly how long your money takes to double.

This result is an estimate only. Check with your bank or the relevant authority before making decisions.

How it is calculated

Rule of 72: years to double = 72 ÷ annual return (%)
Exact: years = ln(2) ÷ ln(1 + return)
Rule of 69.3 is a slightly more accurate version for continuous compounding

For a full projection, use the compound interest calculator.

Worked example

At a 6% yearly return:

Rule of 72: 72 ÷ 6 = 12 years
Exact: ln(2) ÷ ln(1.06) = 11.90 years

Why your number may differ

The rule assumes the same return every year with all gains reinvested. Real returns move up and down, and fees and tax slow doubling. Treat it as a quick estimate, not a forecast.

Frequently asked questions

What is the Rule of 72?

A shortcut: divide 72 by the yearly return in percent to estimate how many years it takes for money to double with compounding.

How accurate is it?

Very close for returns between about 5% and 12%. The exact answer uses logarithms, and the calculator shows both so you can compare.

Does it work for inflation too?

Yes. At 3% inflation, prices double in about 24 years, and the value of your cash halves in the same time.