In order to reduce computing costs in the calculation of combustion in cooktops burning methane-hydrogen mixtures, automatic reduction techniques have been used to develop a reduced mechanism for atmospheric, methane-hydrogen-air flames involving 26 species and 143 reactions starting from GRI-Mech 3.0. Validation for 0-D and 1-D calculations shows good agreement with the original mechanism for gas mixtures ranging from pure methane up to a 1:1 methane-hydrogen ratio, showing that it can be used for a variety of methane-hydrogen mixtures. An improved, customized OpenFOAM solver has been developed and employed to perform 2-D and 3-D calculations. Results from a computational experiment for an axisymmetric, partially premixed flame are in good agreement with the original mechanism and with published experimental results. Flame stability has been studied in realistic 3-D methane-hydrogen cooktop calculations. Using the reduced mechanism, light back phenomena are reproduced accurately while providing a fourfold speed-up over the original mechanism. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.