Sonifications must match listener expectancies about representing data with sound. Three experiments showed the utility of magnitude estimation for this. In Experiment 1, 67 undergraduates judged the sizes of visual stimuli and the temperature, pressure, velocity, size, or dollars they represented. Similarly, in Experiment 2, 132 listeners judged the pitch or tempo of sounds and the data they represented. In both experiments, polarity and scaling preference depended on the conceptual data dimension. In Experiment 3, 60 listeners matched auditory graphs to data created with the results of Experiment 2, providing initial validation of scaling slopes. Magnitude estimation is proposed as a design tool in the development of data sonifications, with the level of polarity preference agreement predicting mapping effectiveness.