Rule of 72 Calculator
Enter the annual interest rate or the number of years to estimate when an investment doubles.
Espacio publicitario
- Years to double
- 9
Espacio publicitario
How the rule of 72 works
The rule of 72 is a quick way to estimate, without complex calculations, how many years it takes to double an investment with compound interest at a fixed rate.
years to double ≈ 72 ÷ annual interest rate
Worked example
At an annual rate of 8%, an investment doubles in approximately 72 ÷ 8 = 9 years.
Frequently asked questions
- Is the rule of 72 exact?
- It's a quick approximation, more accurate for rates between 6% and 10%. For very high or very low rates, the exact result may vary slightly.
- Can it also be used for inflation?
- Yes, it can be used the same way to estimate how many years it takes for the cost of living to double at a given inflation rate.
- What type of interest does the rule of 72 assume?
- It assumes a constant annual compound interest rate, not simple interest.
Related calculators
- Compound interest calculatorCalculate how much your investment will grow with regular contributions and an annual interest rate.
- Mortgage calculatorCalculate your monthly mortgage payment, the principal-interest split and the total cost of the loan, with an amortization chart.
- ROI calculatorCalculate return on investment (ROI) from the initial investment and the profit obtained.
- Currency ConverterConvert an amount between currencies using the exchange rate you enter.
- Simple Interest CalculatorCalculate the interest earned and the total amount with simple interest.