There is disagreement among theorists over the exact measure to be used to quantify auditory level discrimination. It has been proposed that, for level discrimination tasks, the measure that is most linearly related to the sensitivity index, d′, will be the correct measure. The level difference (ΔL) and the Weber fraction (Θ) are both candidates, though the latter is sensitive to the physical unit in which it is expressed (e.g., pressure or intensity) while the former is not. Psychometric functions for level discrimination were obtained at a number of pedestal levels for 10-ms sinusoids (either 1000 or 6500Hz) and broadband noise bursts. These functions were used to assess which of three measures: ΔL, Θ=Δp∕p, or Θ=ΔI∕I, is most nearly linearly related to d′. The results suggest that Δp∕p is the measure that comes closest to being linearly related to d′.