Method for measuring, on a sample composed of a substrate equipped with a coating, the thickness of the coating at at least one preset inspection point, this method comprising a calibrating step comprising the following operations: a) providing a test sample manufactured in the same way as the sample to be inspected; b) selecting, on the test sample, a preset measurement point; c) illuminating the test sample by means of a beam of white light, said beam being focused on the coating at a preset measurement point; d) collecting the portion of the beam transmitted through the test sample; e) establishing the spectrum of the light intensity transmitted through the test sample in a preset wavelength range; f) comparing this spectrum to the spectrum, established beforehand, of the light intensity transmitted, at the same measurement point, through an uncoated sample manufactured in the same way as the sample to be inspected; g) locating a passband common to the two spectra, in which a deviation therebetween may be detected; h) selecting, within this passband, a wavelength corresponding to a deviation between the two spectra; i) measuring the value of the transmitted light intensity corresponding to this wavelength in the spectrum of the test sample and deducing therefrom the transmission coefficient at the wavelength selected in operation h); j) repeating operations a) to d) and i) for a plurality of measurement points; k) physically measuring, at each measurement point, a height difference between a coated zone and an uncoated zone of a sample, corresponding to the actual thickness of the coating; and l) establishing, on the basis of the measurements carried out, a correlation function between, on the one hand, the transmission coefficient at the wavelength selected in operation h), and on the other hand, the thickness of the coating; this method furthermore comprising a measuring step comprising the following operations: m) measuring the light intensity transmitted, at the inspection point, through the wall of the sample to be inspected, at the wavelength selected in operation h); and n) calculating, on the basis of the measurement carried out in operation m) and of the correlation function, the thickness of the coating at the inspection point. a) providing a test sample manufactured in the same way as the sample to be inspected; b) selecting, on the test sample, a preset measurement point; c) illuminating the test sample by means of a beam of white light, said beam being focused on the coating at a preset measurement point; d) collecting the portion of the beam transmitted through the test sample; e) establishing the spectrum of the light intensity transmitted through the test sample in a preset wavelength range; f) comparing this spectrum to the spectrum, established beforehand, of the light intensity transmitted, at the same measurement point, through an uncoated sample manufactured in the same way as the sample to be inspected; g) locating a passband common to the two spectra, in which a deviation therebetween may be detected; h) selecting, within this passband, a wavelength corresponding to a deviation between the two spectra; i) measuring the value of the transmitted light intensity corresponding to this wavelength in the spectrum of the test sample and deducing therefrom the transmission coefficient at the wavelength selected in operation h); j) repeating operations a) to d) and i) for a plurality of measurement points; k) physically measuring, at each measurement point, a height difference between a coated zone and an uncoated zone of a sample, corresponding to the actual thickness of the coating; and l) establishing, on the basis of the measurements carried out, a correlation function between, on the one hand, the transmission coefficient at the wavelength selected in operation h), and on the other hand, the thickness of the coating; m) measuring the light intensity transmitted, at the inspection point, through the wall of the sample to be inspected, at the wavelength selected in operation h); and n) calculating, on the basis of the measurement carried out in operation m) and of the correlation function, the thickness of the coating at the inspection point.