WealthCalc

Rule of 72 calculator

Get a quick sense of how long an investment could take to double if it grew at a steady yearly rate.

Enter 8 for 8%. Use a steady compounded annual rate for this illustration; an average of uneven returns is not equivalent. Positive rates must be at least 0.01%, with a maximum of 50%.

Use the same currency for every amount and a decimal point without thousands separators.

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Approximate time to double

9.00

Years under the chosen steady return

Rule-of-thumb comparison
Assumed annual return8.00%

The Rule of 72 is a shortcut, not an exact calculation or investment forecast. It assumes no extra deposits, withdrawals, taxes or inflation adjustment.

* Not financial advice. Just for fun and information. Read the full Disclaimer, also linked in the footer, for more.

Approximate time to double: 9.00. Years under the chosen steady return.

What the Rule of 72 helps you see

Compounding means that growth can itself earn more growth. This shortcut turns a yearly growth assumption into an approximate waiting time, without needing a starting balance. Enter 8 for an 8% annual return.

Reading your result

At 8%, the rule estimates nine years to double. That is an approximation, not an exact date. It assumes growth stays steady and you neither add nor withdraw money. A zero or negative steady return does not double a positive starting balance.

Actual investments fluctuate. An arithmetic average of uneven yearly returns is not the same as a steady compounded return. Taxes, fees and rising prices can also change what you end up with. The shortcut becomes less accurate at unusual rates; this tool supports positive rates from 0.01% to 50% and non-growing rates down to -50%.

For deposits and inflation, use investment growth. Source: Investor.gov’s Rule of 72 example.

The maths behind the shortcut

Approximate doubling time in years = 72 ÷ annual return in percentage points. At 8%, 72 ÷ 8 = 9. The exact steady annual-compounding time uses logarithms; this calculator intentionally displays the shortcut only.