BW D-Calc is a distribution calculator with a graphic user interface. It displays probability density, and cumulative probability plots, and tabulates percentiles, and parameters for more than 20 distributions. This is a handy tool for use in education, engineering, science and commerce. Typical applications include the preparation of customized probability tables for use with experimental or survey data and as a demonstration device to show how the properties of distributions change with varying input parameters. The distributions are the beta, binomial, Cauchy (Lorenz), Chi-squared, Erlang, exponential, gamma, geometric, Gumbel, inverse Gauss, Laplace, logistic, lognormal, normal, Pareto, Poisson, Rayleigh, Student's T, triangular, uniform, Wald, Weibull. The software is licensed on a single machine basis. The activation code is installed over Internet is specific to the machine from which the software is activated.