Jan 6, 2014 To calculate the interest payment under the 365/360 method, banks multiply the stated interest rate by 365, then divide by 360. However, due to The stated annual interest rate (SAR) is the return on an investment (ROI) that is expressed as a per-year percentage. It is a simple interest rate calculation that does not account for any compounding that occurs throughout the year. The effective annual interest rate (EAR), on the other hand, To calculate the effective interest rate using the EAR formula, follow these steps: 1. Determine the stated interest rate. The stated interest rate (also called the annual percentage rate or nominal rate) is usually found in the headlines of the loan or deposit agreement. Example: “Annual rate 36%, interest charged monthly.” 2.