The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator mMCt . Because of hadronization and parton-showerdynamics, relating mMCt to a field theory mass is difficult. We present a calibration procedure to determinethis relation using hadron level QCD predictions for observables with kinematic mass sensitivity. Fittingeþe− 2-jettiness calculations at next-to-leading-logarithmic and next-to-next-to-leading-logarithmic orderto PYTHIA 8.205, mMCt differs from the pole mass by 900 and 600 MeV, respectively, and agrees with theMSR mass within uncertainties, mMCt ≃ mMSRt;1 GeV.