Summary Noise coefficients of backscattered electron (BSE) detectors for low voltage scanning electron microscopy were studied theoretically and experimentally. The conversion method of BSE detection, the scintillation detector with an acceleration of BSE and detectors with electron multipliers were considered. Formulae for noise coefficients were derived and noise coefficients of detectors were computed for different values of gains of detectors’ components. Theoretical predictions of noise coefficients were compared with experimental results.