CPA

The average amount you spend to win one paying customer. CPA = Total spend ÷ Number of customers acquired. It counts every cost that brought them in, not just the ad click.

CPA tells you whether your marketing actually pays for itself. If it costs more to acquire a customer than they are worth to you, you are buying growth at a loss.

You spend £500 on ads in a week and gain 25 customers. Your CPA is £20. If each customer is worth £60 to you the maths works; if they are worth £15 it does not.