Try the gross effective rate method Total Fees/Total Volume * 100 = Some %.
For Example: Total credit card sales $10,000 fees paid for that $10,000 to be put into the merchant bank account, $400. $400/$10,000 = .04 multiply by 100 to get into a percentage = 4%. In this scenario, 4% is what it costs to accept an electronic payment.
This is how we train our clients. We can go into more detail whenever necessary.
Still confusing, give us a call. We are happy to help.