Cost per click (CPC)

Cost per click is the price an advertiser pays for a single click on an ad, calculated as CPC = ad spend / number of clicks. In auction-based platforms such as search and programmatic advertising, CPC is not a fixed rate card price but the outcome of a real-time bidding auction, influenced by competitor bids, ad relevance or quality scores, and audience demand at that moment.

CPC differs from cost per mille, which prices exposure regardless of engagement, and from cost per acquisition, which prices an actual conversion rather than an intermediate click. A campaign can have a low CPC and still perform poorly if those clicks rarely convert, which is why CPC is usually read alongside click-through rate and downstream conversion metrics rather than in isolation.

CPC is most useful for comparing the efficiency of getting traffic to a site across keywords, ad groups, or channels, and for budgeting campaigns paid on a per-click basis. The common pitfall is optimizing toward the lowest CPC without checking what that cheaper traffic actually does once it lands, since low-cost clicks are sometimes low-intent or, in the case of invalid traffic, not from real users at all.