Abstract Regularities governing perovskite formability are investigated, by using empirical structure map methods and a total of 197 binary oxide systems. Each of the 197 systems belongs to one of the three groups (A 2 O–B 2 O 5 , AO–BO 2 and A 2 O 3 –B 2 O 3 ), and among them only 121 systems have a perovskite compound. It is found that the octahedral factor, r B / r O , is as important as the tolerance factor, (r A +r O )/ 2 (r B +r O ) , with regards to the formability of perovskite. On the structure map constructed by these two parameters, sample points representing systems of forming (perovskite) and non-forming, are distributed in distinctively different regions. Prediction criterions for the formabilities of perovskites are obtained, by which only four systems are misclassified. The developed models can be used to search for new perovskites by screening all possible elemental combinations in any of the above three groups. It may assist in the design of new substrate or buffer materials for semiconductors where perovskite can play an important role.