Orthonormal scales should be used for Nyquist impedance plots. The length from 0 to 1 along the imaginary axis should be equal to the length from 0 to 1 along the real axis. Otherwise, semicircle graphs are not semicircles and it becomes difficult to measure angles. This Demonstration presents two examples: the impedance for a Tafelian redox system and the Randles circuit with Warburg impedance. Orthonormal and non-orthonormal plots are compared (blue curves and scale: non-orthonormal scale; orange curves and scale: orthonormal scale).