Comparison of different H i empirical relations. (Left) Estimated empirical slopes of optical/NIR H i lines from the literature (Alcalá et al. 2017; Rogers et al. 2024; Salyk et al. 2013) and mid-infrared H i lines from this work. The colour bar and marker colours indicate the wavelength of each H i transition. The median slope of the distribution is ∼1.1, shown with a dashed line. The slope of the Paα empirical relation (Rogers et al. 2024) is slightly offset from other H i lines, as it was calibrated using JWST spectra of young stars in the Large Magellanic Cloud (LMC), which has sub-solar metallicity. This lower metallicity likely affects the slope. (Right) Comparison of empirical relations between accretion luminosity (log L_acc) and line luminosity (log L_line) for representative H i transitions from optical to mid-infrared wavelengths. The slopes are consistent across this wide wavelength range.