A calibration curve for the response of commercial Manganin gauges upon unloading in plane dynamic experiments is presented. The data obtained from 18 plane impact experiments cover shock stresses in the 1.5–15 GPa range and involves various materials. The calibration curve was drawn through normalized data points. The normalization is based on the assumption that the ratio between resistances of the gauge at the shock and unloading states depends on the ratio of the respective stresses.