Rule of 72 Calculator
Estimate doubling time with the Rule of 72.
How fast money doubles
The Rule of 72 is a mental-math shortcut: divide 72 by the annual return to estimate years to double. At 8%, money doubles in about nine years — close to the exact figure without a calculator.
It also works for inflation, showing how fast prices double and buying power halves — at 3% inflation, money loses half its value in about 24 years.
An approximation
It is most accurate for rates between 6% and 10%; extremes drift. Your inputs never leave your device.
Frequently Asked Questions
How does this rule of 72 calculator work?
It uses the numbers you enter and applies the visible formula or planning rule in your browser.
Is this financial advice?
No. This is an educational estimate for planning. Check important decisions with a qualified financial professional.
Are my numbers uploaded?
No. The calculation runs locally in your browser and nothing is stored by this page.
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