Several different measures were employed in the literature to describe performance by human observers in intensity discrimination tasks. These measures include the different limen (DL) or .DELTA.I [change in power] in dB, the Weber fraction (.DELTA.I/I), and signal-to-masker ratio (Ps/Pm). The mathematical relationship among these measures is described for conditions in which masker and signal are sinusoids of the same frequency, sinusoids of different frequencies and noise waveforms. A table is provided which contains values of each of these measures, describing equivalent performance over the typical range obtained in most intensity discrimination experiments. Some cautions should be observed in choosing and reporting particular measures of intensity discrimination.