In this study, 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 used to obtain a flicker estimation method based on the International Electrotechnical Commission (IEC) flickermeter. In the proposed method, the frequency domain components of the voltage 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 three different electrical arc furnace (EAF) plants, where the flicker level is considerably high compared to other types of loads. The comparison of the results with the digital realisation 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 significantly. Since the frequency decomposition is obtained by using Kalman filtering, no leakage effect of the fast Fourier transform (FFT) method is involved in case of frequency deviations.