Rare earth-doped materials are successfully utilized as non-contact optical temperature sensors. Thermal sensing is usually based on the ratiometric technique between two separate emission lines originated from thermally-coupled levels. We study Gd₂O₃:Eu³⁺ 1 at.% and YAG: Eu³⁺ 4 at.% phosphors as luminescence thermometers in 298–473 K range using both conventional experimental and Judd-Ofelt based theoretical approaches. Thermometric performances of suggested sensors were quantified through absolute and relative thermal sensitivities and temperature resolution. Experiment and theoretical modelling gave similar results. This proves the theoretical model as a simple and fast method for estimation of the Eu³⁺-doped thermometer perspectives.