1. A method of determining pitch of lithographic features of a mask, comprising: determining a bias based on interactions caused by enlargement between a plurality of reference lithographic features representative of all actual mask design lithographic features positioned according to a lithographic printing parameter of the mask; applying the determined bias to a plurality of actual lithographic features of the mask design, the number of the plurality of actual lithographic features being greater than the number of reference lithographic features; and determining pitch of the plurality of actual lithographic features based on interactions between the biased plurality of actual lithographic features.