Another source of uncertainty is that failing to compute all isomers for a composition will lead to erroneous E min values. Our dataset, QM9, is derived from GDB-17 and should include most enumerable isomers, so our calculated E min values should accurately reflect the energy above the most stable isomer. We studied the effect of undersampling, either in QM9 or future efforts, by computing E min with only 100 isomers per composition. Even with a severe undersampling, E min 's accuracy for predicting synthesizability only changes negligibly (see supplemental ??). Molecules outside of QM9 will likely not have calculated energies for all isomers readily available, so we also calculated in ?? the probability of excluding the lowest energy isomers when randomly sampling isomers for calculating E min . Randomly sampling 100 isomers from 100000 enumerable isomers has only a < 2% chance of excluding isomers within the lowest 4% of energies. Therefore, including enough isomers to confidently calculate E min should be a feasible task if one does not wish to calculate energies for all enumerable isomers.