A simple way for a merchant to calculate on average what a credit card costs him or her to accept. Simple calculation is done by dividing total fees by total sales volume from the merchant statement, & multiplying by 100 to get a %. For example, total sales $20,000 total fees $800. $800/$20000 = .04 * 100 = 4%. If this is your gross effective rate, please give us a call. We will save you some money.