Piezoresistive carbon sensors were used to determine the stress‐time history in unsintered powders during shock‐wave compaction in a gas gun. Powders of both spherical and irregular shape were examined, including steel, aluminum–silicon alloy, copper, tungsten, and aluminum nitride. A calibration relationship was established between direct sensor response and stress levels determined by impedance matching; it corrects apparent systematic errors in the manufacturer’s calibration for stresses in excess of about 2.0 GPa.