Rule of 72

Estimate doubling time from a rate, or the rate needed to double in a given number of years. Shows both the Rule of 72 estimate and the exact calculation.

Annual Interest Rate (%)

Enter a rate to estimate years to double.

Estimate (Rule of 72):

Exact (ln(2)/ln(1+rate)):

Years to Double

Enter years to estimate required annual rate.

Estimate (Rule of 72):

Exact: