Abstract: Computer-readable media, computer systems, and computing devices for responding to advertising inventory queries that specify frequency caps limiting the number of impressions that are shown to a unique user. Impression logs are retrieved from logging servers and processed to generate a unique user distribution that provides information regarding the numbers of unique users that receive ad impressions at a specified location and during a specified time period. Estimates of frequency-capped capacity to fulfill a booking request and estimates of frequency-capped availability of inventory are computed using the unique user distribution.