FT-Raman spectroscopy was used as an alternative to typical thermogravimetric techniques in order to determine the filler content in calcium carbonate/high-density polyethylene composites. As predicted, the selected band ratio had good linearity with the volume fraction ratio of filler and matrix even at a high filler content, up to 75% of the weight fraction. FT-Raman spectroscopy provided comparable results compared to values obtained from thermogravimetric analysis.