A general empirical relationship has been developed for estimating the cloud point of pure nonionic surfactants of the allyl ethoxylate class. For a set of 62 structures, composed of linear alkyl, branched alkyl, cyclic alkyl, and alkylphenyl ethoxylates, cloud points can be estimated to an accuracy of +/-6.3 degrees C (3.7 degrees C median error) using the logarithm of the number of ethylene oxide residues and three topological descriptors that account for hydrophobic domain variation.