Polyoxyl 20 cetostearyl ether, also known as ceteareth-20, is a cetostearyl alcohol-based polymer containing a terminal poly(oxyethylene) fragment and commonly used as a surfactant and as an emulsifier in moisturizers, conditioners, exfoliants, and sunscreens, among others. In this application note, we demonstrate that benchtop NMR spectroscopy can perform the average polymer length test as described by the current USP-NF monograph method.