sHR diagram showing our results from the analysis for 527 stars with O9–B5 spectral type color-coded by their luminosity class, and 191 O-type stars from Hol18-22 in gray. The boundaries of our model grid are indicated with a rectangle. The shaded area indicates the approximate region where our results correspond to the upper or lower limits (see Sect. 3.2.4). The approximate separation between the O- and B-type stars is indicated with a dotted diagonal black line. For reference, the figure includes nonrotating evolutionary tracks with solar metallicity from the Geneva and Bonn models (Ekström et al. 2012; Georgy et al. 2013; Brott et al. 2011, respectively). Intervals of the same age difference are marked with purple crosses for Geneva and green triangles for Bonn, which are connected with dashed and dash-dotted lines of the same color. The dash-dotted gray lines indicate different constant log g values.