Summary of our results and results of other teams on K2-18b metallicity. The error bars of our results corresponds to the simulations that were within the 1σ confidence level against Tsiaras et al. (2019) data. The O/H and C/H ratio of the other works were estimated assuming [H₂ ] + [He] + [H₂O] + [CH₄ ] = 1 and a solar He/H. The C/H upper limit of Benneke et al. (2019) and Madhusudhan et al. (2020) corresponds respectively to the 2σ and the 99% upper limit. The dotted line represents the metallicity expected for the mass of K2-18 b using the linear fit in Fig. 23, based on solar-system C/H ratios.