Gas masses of the Herbig disks detected in the CO isotopologues as selected from the models presented in Fig. 5. The disks are ordered from left to right by increasing ¹³CO luminosity. The gray lines indicate the range in possible disk mass based on the disk parameters listed in Table 1, while the black lines indicate the standard deviation. The mean mass of these models is given as the dark blue diamond. After removing models which are potentially gravitationally unstable, the mean mass changes into the light blue diamond. The orange diamonds are taken from the dust masses of Stapper et al. (2022) multiplied by the canonical gas-to-dust ratio of 100. The HD upper limits from Kama et al. (2020) are shown as green downward pointing triangles. The C¹⁸O lower limits are directly obtained from the integrated flux. The middle panel shows the resulting gas-to-dust ratio based on the mass range and mean values, and the top panel shows the factor by which the mass could be underestimated when using C¹⁸O assuming optically thin emission.