This paper reports the results of experiments performed in an effort to find a formulaic relationship between the interaural waveform coherence of a band of noise γW and the interaural envelope coherence of the noise band γE. An interdependence described by γE=π/4+(1−π/4)(γW)2.1 is found. This relationship holds true both in a computer experiment and for binaural measurements made in two rooms using a KEMAR manikin. Room measurements are used to derive a measure of reliability for the formula. Ultimately, a user who knows the waveform coherence can predict the envelope coherence with a small degree of uncertainty.