Ad rendering parameters for a set of two or more ads may be determined by (a) accepting, for a set of two or more ads, ad information including at least one ad feature having a value that depends on ad rendering parameters, and (b) determining ad rendering parameters for at least one ad from the set of two or more ads using the accepted ad information. Ad rendering parameters may be determined using accepted ad rendering constraints. The ad rendering constraints may include space available and/or a maximum number of ads permitted to be rendered. The act of determining ad rendering parameters may include maximizing a value associated with serving at least one ad from the set of two or more ads with ad rendering parameters subject to the ad rendering constraints. The ad rendering parameters may include sizes of the served ads, and/or a layout of the served ads.