Abstract The analysis is made of the error in the momentum determination for charged particles in nuclear emulsion exposed in a 180 kG magnetic field. The measurement technique is described and the influence of various sources of errors is discussed. The formulas are given for the error of the momentum determination by means of the described techniques. The results of measurements on 24 GeV protons were analysed. The momentum values and their spreads, obtained experimentally, were compared with the corresponding expected values. The experimental values are consistent with the expected values. The mean error of the momentum determination based on 4 cm sections of 24 GeV/ c proton tracks is ∼ 11%/