Definition: Cost Per Lead (CPL) is the total cost of marketing to acquire a lead. It is an online pricing model used for digital marketing where the advertiser pays for the explicit sign-up from a consumer interested in advertisers offer. It's a key metric to measure effectiveness of your online marketing campaigns. 

Example: Consider your company spent $1,000 on your Pay-Per-Click (PPC) campaign and 10 users convert to leads: Cost per lead = $1,000/10 = $100. A $100 per lead is effective for a luxury car campaign and highly ineffective for a toy store and will require the advertiser to readjust it's PPC.

Business Insight: It's very important for you to benchmark your CPLs to your industry, competitors and size of your company.