An improved determination of electroweak parameters using H1 inclusive neutral and charged current deep inelastic scattering cross section data is presented. The analysis benefits from the use of the previously published data with longitudinally polarised lepton beams. The parameters are determined in a combined fit of the electroweak parameters together with PDFs. The predictions include NNLO QCD corrections for the PDF and structure function calculations, and the corrections at the leptonic vertex are obtained in the on-shell scheme including the full set of one-loop corrections. The analysis determines the weak neutral-current couplings of the light quarks as well as potential contributions beyond the SM. The mass of the W-boson is determined with a precision of 115 MeV in the space-like regime.