We quantify and examine the uncertainties in predictions of the lightest $$CP$$ CP even Higgs boson pole mass $$M_h$$ Mh in the Minimal Supersymmetric Standard Model ($${\text {MSSM}}$$ MSSM ), utilising current spectrum generators and including some three-loop corrections. There are two broadly different approximations being used: effective field theory (EFT) where an effective Standard Model ($$\text {SM}$$ SM ) is used below a supersymmetric mass scale, and a fixed order calculation, where the $${\text {MSSM}}$$ MSSM is matched to $$\text {QCD}\times \text {QED}$$ QCD×QED at the electroweak scale. The uncertainties on the $$M_h$$ Mh prediction in each approach are broken down into logarithmic and finite pieces. The inferred values of the stop mass parameters are sensitively dependent upon the precision of the prediction for $$M_h$$ Mh . The fixed order calculation appears to be more accurate below a supersymmetry (SUSY) mass scale of $$M_S\approx 1.2~\text {TeV}$$ MS≈1.2TeV , whereas above this scale, the EFT calculation is more accurate. We also revisit the range of the lightest stop mass across fine-tuned parameter space that has an appropriate stable vacuum and is compatible with the lightest $$CP$$ CP even Higgs boson h being identified with the one discovered at the ATLAS and CMS experiments in 2012; we achieve a maximum value of $$\sim 10^{11}$$ ∼1011 GeV.