1. A method comprising: (a) collecting, by a computing device, data on delivery of a plurality of video media to users and delivery of ads during playback of each of the plurality of video media, the delivery of ads based on applying ad insertion rules during playback of video media, each of the ad insertion rules comprising a format of an ad, insertion points for the ad, and a rule criteria which specifies criteria to trigger the ad insertion rule, (b) identifying, by the computing device and from the collected data, a number of times each of a plurality of video media was played during a time period; (c) identifying, by the computing device and from the collected data, a number of ads delivered via the ad insertion rules at a plurality of insertion points during playback of each of the plurality of video media over the time period; (d) receiving, by the computing device, input identifying an ad requested to be delivered during playback of the plurality of video media by applying a set of ad insertion rules; and (e) determining, by the computing device, a forecast of a total inventory for the requested ad based on the identified number of times each of the plurality of video media was played, the identified number of ads delivered during playback of each of the plurality of video media and the identified set of ad insertion rules.