Abstract Judd–Ofelt theory is a cornerstone of lanthanides’ spectroscopy given that it describes 4f n emissions and absorptions of lanthanide ions using only three intensity parameters. A self-referenced technique for computing Judd–Ofelt intensity parameters from the excitation spectra of Eu 3+ -activated luminescent materials is presented in this study along with an explanation of the parametrisation procedure and free user-friendly web application. It uses the integrated intensities of the 7 F 0  →  5 D 2 , 7 F 0  →  5 D 4 , and 7 F 0  →  5 L 6 transitions in the excitation spectrum for estimation and the integrated intensity of the 7 F 0  →  5 D 1 magnetic dipole transition for calibration. This approach facilitates an effortless derivation of the Ω 6 intensity parameter, which is challenging to compute precisely by Krupke’s parametrisation of the emission spectrum and, therefore, often omitted in published research papers. Compared to the parametrisation of absorption spectra, the described method is more accurate, can be applied to any material form, and requires a single excitation spectrum.