An online system provides identifies multiple candidate budgets to an advertiser requesting presentation of advertisements via the online system. The advertiser may select a candidate budget used for presenting advertisements via the online system. A default budget may be identified from the candidate budgets to increase the likelihood of the advertiser selecting the default budget. The candidate budgets and the default budget are determined by the online system to maximize the likelihood that an advertiser elects to present advertisements via the online system or to maximize revenue received the online system for presenting advertisements from the advertiser. Various factors are specific to the advertiser, the object being advertised, and other contextual information may be used to determine the candidate budgets.