Calculate your cost per lead as a function of total marketing spend, and total leads generated from marketing.
Compare your cost per lead with the average CPL in your industry.
Calculate channel-specific CPL as a function of marketing spend and leads generated on each channel.
Calculate your revenue per lead based on the estimated revenue each customer generates and your lead-to-customer conversion rate.
Compare your cost and revenue per lead to determine positive or negative ROI.
Compare channel-specific CPL against both each other and your overarching CPL.
Re-evaluate your CPL at least once per quarter to measure trends and adjust your marketing tactics as needed.