Sea ice develops a porous structure as impurities from sea water are rejected during freezing. This study revisits factors regulating noble gas inclusion in sea ice and, for the first time, parameterizes the bulk sea ice–sea water partition coefficient ( k iw )—the ratio of concentrations in sea ice to sea water—as a function of ice properties. Ten sea-water freezing experiments were conducted in a gas-tight chamber to quantify gas partitioning. Experimental k iw spanned k iw, helium = 1.31–1.90, k iw, neon = 0.29–1.34, k iw, krypton = 0.12–0.67, k iw, xenon = 0.12–0.66 and k iw, salt = 0.15–0.49, reflecting variations in ice growth rates and properties. Partitioning trends were analyzed against ice temperature, salinity and growth rate ( n = 10) and brine porosity ( n = 8). Bulk sea-ice salinity was the statistically strongest indicator of k iw and predicted >70% of variability in k iw, krypton and k iw, xenon . Doubling ice salinity (e.g. from 5 to 10) increased k iw by 140–150% for krypton and xenon. Neon did not exhibit statistically significant trends in k iw with ice properties, likely due to its small size and low solubility facilitating bubble nucleation and/or crystal lattice inclusion. Gases larger than the ice-Ih cavity radius showed nearly identical k iw , consistent with firn diffusion models.