Periodic Interest Rate Calculator

Calculator Use

Use this calculator to calculate P, the effective interest rate for each compounding period. P = R/m where R is the annual rate.  For example, you want to know the daily periodic rate for a credit card that has 18% annual interest; enter 18% and 365.

Interest Rate (R)

is the nominal interest rate or "stated rate" in percent. r = R/100

Compounding Periods (m)

is the number of times compounding will occur during a period.

Periodic Interest Rate (P)

This is the rate per compounding period, such as per month when your period is year and compounding is 12 times per year.

Interest rate can be for any period not just a year as long as compounding is per this same time unit.  For example, your stated rate is 9% per quarter compounded monthly.  Enter 9% and 3 (for 3 months per quarter to get P = 3%, the effective rate per month.  Side Note: the effective rate calculation tells us the effective rate per quarter in this case is 9.2727%.