Annual percentage yield (APY)

The effective, or true annual rate of return. The APY is the rate actually earned or paid in one year, taking into account the effect of compounding. The APY is calculated by taking one plus the periodic rate, raising it to the number of periods in a year and then subtracting one. For example, a 1% per month rate has an APY of 12.68% (1.01^12 -1).