The frequency spectrum of a 1/50 microsec impulse wave is obtained by the use of the Fourier transform. The corresponding frequency spectrum of the output from a simple capacitance potential divider, suitable for use up to 300 kV, is calculated from the input frequency spectrum for a 1/50 microsec wave and the frequency response of the divider, measured up to about 3 Mc/s. From this output frequency spectrum the output at a time of 1 microsec is calculated, and thus the divider ratio, suitable for peak-voltage measurements, is estimated. Consideration is given to errors due to the limited frequency range of the measurements, and the accuracy of the measurement of the divider ratio is estimated to be better than ±1%.