We report on a new determination of the <overline>MS</overline> charm quark mass from charmonium sum rules using perturbative QCD input at O(α3s). We establish two improvements over corresponding previous analyses: (i) all available experimental data for the hadronic R-ratio up to √s = 10.538 GeV are included for the experimental moments and (ii) a detailed analysis of perturbative uncertainties (due to the truncation of the perturbative series) is carried out. Issue (i) avoids having to rely on theoretical model input in the data region 4.8 GeV <√s <10.538 GeV and (ii) is crucial for a reliable estimate of the error. Our final result  is m̄c(m̄c) = 1.277±0.026 GeV, with an error twice as large than the one obtained in Ref. [2, 3].