Rule of 25 Calculator

What is the Rule of 25?

The Rule of 25 is a simplified formula used to estimate the number of years it will take for an investment to double in value, based on a fixed annual interest rate. It's a quick mental calculation method that provides a close approximation to the more precise Rule of 72 or Rule of 69.

How to Use This Calculator

1. Enter the annual interest rate in the input field (as a percentage, without the % sign)
2. Click the "Calculate" button to compute the years to double
3. The result will be displayed in the Results section

Example

If you have an investment with an annual interest rate of 5%, you would enter 5 in the calculator. The result would be approximately 5 years (25 ÷ 5 = 5), meaning it would take about 5 years for your investment to double in value.

Limitations of the Rule of 25

The Rule of 25 is an approximation and works best for lower interest rates. For higher interest rates, the accuracy decreases compared to the more commonly used Rule of 72. It also assumes a constant interest rate and does not account for compounding frequency or other investment variables.

When to Use This Calculator

This calculator is useful for:

• Quickly estimating investment growth
• Understanding the impact of different interest rates on investment doubling time
• Financial education and learning basic investment concepts