Rule of 72 Calculator

Find how long it takes to double your money at a given rate, or the rate needed to double in a set number of years. The exact compound answer is shown next to the shortcut.

Read the guide: How the Rule of 72 Works (Doubling Your Money Fast)

Doubling time

Solve for

Years to double

9 yrs

exact: 9.01 yrs

Rule of 72
9 yrs
Exact compound
9.01 yrs

The shortcut is tight from about 6–10% and drifts above ~20%, where the exact compound figure is more reliable. Divide by an inflation rate instead to see when buying power halves.

How it works

  1. 1

    Pick what to solve

    Solve for the years to double, or for the rate to double in N years.

  2. 2

    Enter your figure

    Add the annual rate, or the number of years.

  3. 3

    Compare answers

    See the Rule of 72 estimate beside the exact compound figure.

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Every calculation runs locally in your browser. The income, balances and goals you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.

Frequently asked questions

How does the Rule of 72 work?
Divide 72 by the annual rate of return to estimate the years needed to double your money. At 8%, 72 ÷ 8 = 9 years.
How do I find the rate to double in a set number of years?
Divide 72 by the number of years. To double in six years, 72 ÷ 6 = 12, so you would need about a 12% annual return.
How accurate is the Rule of 72?
It is most accurate for rates between 6% and 10%, with error under 1%. Above roughly 20% it underestimates the doubling time, so use the exact compound figure for high-return cases.
Can I use it for inflation?
Yes. Divide 72 by the inflation rate to estimate how long until your money’s buying power halves. At 3% inflation, that is about 24 years.
Is this financial advice?
No. These are estimates to help you plan and compare options. Your real figures depend on your lender, taxes and personal situation, so check with a qualified professional before deciding.

Important

For information and planning only — not financial, tax or legal advice. These figures are estimates; rates, fees and rules vary, so confirm anything that affects a real decision with a qualified professional or the official source.

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