Since we aggregate force uncertainties over atoms, the number of atoms per data point is important and we chose three data sets examining a large variety of system sizes and configurations. 1) Transition1x 12 features nudged elastic band (NEB) searches for a wide range of organic reactions in gas phase with 7 to 23 H, C, N, and O atoms, and thus resembles rather small systems without periodic boundary conditions. From each reaction, we only used the last, converged reaction pathways made up of ten images each, where indices 1, 2, 9, and 10 were used as training and validation set. The test set can thus be split into different indices corresponding to a different level of extrapolation from the training configurations. 2) Surface reconstructions of crystalline SrTiO 3 were taken from Ref. 42, and feature 136 Sr, Ti, and O atoms per data point, thus resembling large systems with periodic boundary conditions. 3) A liquid water data set from Ref. 45 features 192 H and O atoms per data point, and thus resembles a large, homogeneous system with periodic boundary conditions that lends itself to dissecting the overall simulation cell into smaller sub-regions. On each dataset, we trained a five-membered ensemble of the equivariant message-passing neural network MACE. See Methods for further details.