An analysis of the intensity ratios, adsorbate over substrate and substrate over the clean one, is carried out, treating them as a system of two independent variables. This leads to simple formulas, ready to be applied to the determination of coverage up to the monolayer point, if elemental bulk standards are available. The procedure allows one more parameter to be found out compared with previous treatments. Formulas are produced for polycrystalline and single crystal elemental bulk standards. The coverage thus calculated turns out to be a function of the intensity from the adsorbate over that from the clean substrate. The analysis is applied successfully to the adsorption of Ba on the Ni(110) surface at submonolayer regime.