In this paper, a Matlab software performing numerical Volterra distortion analysis of a weakly nonlinear circuit with arbitrary multiport topology is described. Due to numerical convolution of signal spectrums, the degree of nonlinearity is relatively easy to increase, and the amount of signal tones is not limited to one or two. Distortion products are displayed graphically as vector sums of all different contributions. This makes it easy to recognize the dominant distortion source and possible cancellation mechanisms, and aids the designer to improve the design.