Abstract Ice pigging is a process used by many industries for pipe cleaning and product recovery. Ice slurries, used to form an ice pig, are generated using an aqueous solution of water and a freezing point depressant, typically salt (NaCl) at 5% salinity. The ‘thickness’ of an ice slurry is key to the ice pig's performance, and this paper investigates a new non-invasive method of ice fraction measurement. Electromagnetic (EM) waves, with a frequency of 2.5 GHz, are absorbed rapidly by water molecules, but pass through ice with little drop in intensity, due to key differences in the materials' atomic structures. This phenomenon is exploited, and results show ice fraction can be approximated to within ±1.2% using a VNA spectrum analyser, then mathematical manipulation and analysis. This rivals the error in calorimetry, ±1.3%, which currently seen as the ‘gold standard’ in ice fraction measurement across the industry.