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Rule of 72 Calculator

Estimate how many years it takes money to double at a given interest rate (or the rate needed to double in N years).

Enter values

Results update as you type.

Result

Rule of 72 estimate

9 years

Exact doubling time
9.006 years

About the Rule of 72 Calculator

Estimate how many years it takes money to double at a given interest rate (or the rate needed to double in N years).

Also known as: doubling time, rule of 72, how long to double money, rule of 70.

How to use this calculator

  1. Enter find.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Years to double ≈ 72 ÷ annual rate (%)

Worked example

Using the values pre-filled in the calculator above:

  • Find: Years to double
  • Annual return = 8 %

the calculator returns:

  • Rule of 72 estimate: 9 years
  • Exact doubling time: 9.006 years