EPC stands for "Earnings Per Click" and is a great way to determine which offer performs better between two offers with different payouts. 

When comparing two offers, one with a $36 payout and another with a $40 payout, a common mistake made by affiliates is that they assume that the $40 payout will be the better offer. Offer A with a $36 payout receives 100 leads earning the affiliate $3,600. We can now calculate the EPC by dividing $3,600 by the total clicks 700 to get the EPC of $5.14. Offer B with a $40 payout receives 70 leads earning the affiliate $2,800. Offer B received the same amount of clicks so let's divide $2,800 by 700 to calculate a $4.00 EPC for that offer. So based on the stats Offer A's epc is $5.14 compared to Offer B's EPC of $4.00 which shows that an offer with a higher payout is not always the better offer. In this example Offer A earns the affiliate $1.14 per click more then Offer B that's an extra $800 of revenue.

EPC can also be used in optimizing marketing campaigns. The EPC allows the affiliate to know what their CPC 'cost per click' must stay below in order to make the campaign profitable.