Abstract: A hand-held, battery-powered harmonic distortion meter reduces the level of the AC power waveform of interest to a level compatible with the measurements to be performed, converts successive portions of the reduced waveform to digital representations in a multi-bit format for processing, stores a predetermined number of sequences of the digital representations, processes the stored sequences according to a fast Fourier transform algorithm using time decomposition with input bit reversal to produce intermediate calculations of the real and imaginary parts of the DC, fundamental frequency and harmonic components of the input waveform, further processes the intermediate calculations to obtain various parameters of the input waveform including magnitude of the harmonic components as a percentage of the fundamental frequency of the waveform, and selectively displays the final calculations according to switch selections on the face of the meter.