Comparison between R_e and the physically motivated size parameter for UDGs and dwarfs. Top: R_e–stellar mass relation (left) and the R₁–stellar mass relation (right) for dwarfs (grey) and UDGs (colours). The best-fit line of each relation for the dwarf sample is also over-plotted. The upper left corner of each plot shows the typical uncertainty in our measurements (see TCK20). Bottom: histograms showing the distribution of R_e/R_e, fit (left) and R₁/R_1,fit (right) where “fit” refers to the best-fit line of each relation for the dwarf sample.