Cost per enquiry
What it costs, on average, for one person to contact you after a campaign.
Technical meaning
Ad spend divided by the number of incoming enquiries (form, call, booking). Contrast always distinguishes raw enquiries from qualified enquiries, meaning those that match the target client. A low cost per enquiry is worthless if enquiries do not become clients.
Formula
Cost per enquiry = ad spend ÷ number of enquiries