Polyhydroxyalkanoates (PHAs) are polyesters produced by bacterial fermentation of carbon sources, such as lipids or sugars. As biomaterials, these polymers have been proposed as an attractive alternative to non-renewable petroleum resources to make various consumer products. Typically, the polymer compositions in PHAs are determined using gas-chromatography-mass spectrometry (GC-MS), gas chromatography with a flame ionization detector (GC-FID), or 1H nuclear magnetic resonance (NMR) spectroscopy. In this application note, we demonstrate that benchtop 1H NMR spectroscopy can be used to determine polymer compositions in PHAs accurately and quickly.