In this paper, a Kalman filtering based approach is proposed to measure the light flicker of the electricity transmission systems. Analytical expressions of the instantaneous light flicker sensation are obtained beginning from a voltage waveform and these expressions are used to obtain a flicker estimation method based on the IEC (International Electrotechnical Commission) flickermeter. In the proposed method, the frequency domain components of the waveform are obtained by Kalman filtering and these components are used to obtain the light flicker. The method is tested on both simulated data and field data obtained from a power system. The comparison of the results with the digital realization of the IEC flickermeter shows that the method gives satisfactory estimations with low computational complexity. The method is especially useful for conditions such as disturbances and subsequent system transients where the system frequency deviates. Since the frequency decomposition is obtained by using Kalman filtering, no leakage effect of the FFT method is involved in case of frequency deviations.