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Rule of 72 Calculator
Estimate how many years it may take an investment to double at a fixed annual return using the Rule of 72.
- Free to use
- Runs in your browser
- Level A · Standard formula
- Last reviewed 2026-08-16
Calculator guide
How to use the Rule of 72 Calculator
Estimate how many years it may take an investment to double at a fixed annual return using the Rule of 72. Enter the requested values and select Calculate. The result and supporting values are produced locally in your browser.
Formula
Worked example
At an 8% annual return, the Rule of 72 estimates a doubling time of about 9 years.
What to keep in mind
- The Rule of 72 is a mental-math approximation, not an exact compound-interest calculation.
- Accuracy varies with the rate; use a compound-interest calculator when precision matters.
Methodology
This calculator uses deterministic arithmetic and performs the calculation locally in your browser. Verify assumptions, units, and source values for your specific use case.
Review standard: Level A · Standard formula. How calculator reviews work.
Frequently asked questions
What does this calculator calculate?
Estimate how many years it may take an investment to double at a fixed annual return using the Rule of 72.
How is the result calculated?
Estimated Doubling Time ≈ 72 ÷ Annual Return Rate (%).
Can I use the result for an important decision?
Use the result as a calculation aid and verify the inputs, assumptions, and applicable professional or regulatory requirements before relying on it for an important decision.
Does CalculateMeasure store the values I enter?
The calculator performs its arithmetic in your browser. The calculator itself does not need to send your entered values to a server to produce the result.