Previously, local first-order sensitivity analysis was available to calculate sensitivities of species concentrations to thermochemistry and rate constants. New methods for both local and global uncertainty analysis have been implemented in RMG. Local uncertainty analysis builds on those first-order sensitivity by incorporating estimated uncertainties for thermochemical and rate parameters to obtain uncertainties for species concentrations. Global uncertainty analysis uses the MIT Uncertainty Quantification Library (MUQ 2) 20 to construct polynomial chaos expansions (PCEs) based on reactor simulations at random points within the uncertainty space of the input thermochemical and rate parameters. Reactor simulations are performed using Cantera. A key feature of the RMG uncertainty module is the ability to track correlated uncertainties in model input parameters, such as correlations arising from group additivity estimates for thermochemistry and rate rule estimates for rate coefficients. This can have significant effects on uncertainty propagation and the resulting uncertainties on output parameters.