Rule of 72 Calculator

The Rule of 72 is a simple formula used to estimate the doubling time of an investment. It's a quick way to understand how long it will take for your money to double at a given interest rate.

We offer more precise calculators for your specific needs like the rule of 70, rule of 69.3 and an exact formula to calculate the doubling time. But when you're in a hurry the rule of 72 is a good estimator.

Calculation Methods

Rule of 72
Most commonly used due to its simplicity and being easily divisible. Works well for common interest rates and quick estimates.
Time = 72 / rWhere r is the annual interest rate.

Rule of 70
More accurate for higher interest rates (>10%). Often used in financial analysis.
Time = 70 / rWhere r is the annual interest rate.

Rule of 69.3
Most accurate for continuous compounding. Derived from the natural logarithm of 2.
Time = 69.3 / rWhere r is the annual interest rate.

Exact Formula
Uses natural logarithms for precise calculations. Most accurate but requires a calculator, which is no problem here.
Time = ln(2) / ln(1 + r/100)Where r is the annual interest rate.