A method of determining a film coating thickness on a substrate and/or amount one or more compositional ingredients of said film coating including making mid-IR spectra of a series of coating thickness or coating weight standards (and/or composition standards) on an appropriate substrate material to match sample material in question, pre-processing the data to prepare it for multivariate calibration methods, performing the multivariate calibration, saving the calibration model in the hand-held mid-IR device in an appropriate format, and using the calibration model to predict sample material in question from their mid IR spectra.