Methods, systems, user interfaces, and apparatus, including computer programs encoded on a computer-readable storage medium, for providing performance estimates for a content campaign. A method includes identifying a campaign including one or more targeting criteria for targeting content items to users; identifying historical auction results; storing the historical auction results as a plurality of documents; evaluating the plurality of documents to determine an estimated number of impressions that would occur in the plurality of documents based on the targeting criteria; determining an estimated total number of impressions for the targeting criteria in the time period based at least in part on the estimated number of impressions in the plurality of documents; and determining a total number of unique targeted users including determining a frequency of impression and determining the total number of unique targeted users as the total number of impressions divided by the frequency of impression.