Rule of 72 Calculator
Finance
Estimate the time needed to double an investment.
Formula
Approximate doubling time = 72 / rate in percent
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- A heuristic, not an exact compounding calculation.
Example Calculation
Example inputs
- Annual growth rate: 6 %
At 6% growth, the Rule of 72 estimates 12 years to double.
Frequently asked questions
How do I use this calculator?
Enter annual growth rate. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Approximate doubling time = 72 / rate in percent. A heuristic, not an exact compounding calculation.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.