Mathematic models have been used for several decades to predict the severity of burn injury that would result from application of a given thermal stress to the surface of the skin. Solution of the governing mathematic equations has been achieved either by analytic methods, with required simplifying assumptions that may compromise the rigor with which the results are applied, or by numeric methods, which require programming of finite element or finite difference codes in computer languages. In recent years microcomputer hardware and the associated software have become both powerful and relatively simple to use, and the price per unit of computing capability has dropped dramatically. Thus it is now possible to perform on a desktop machine with relative case calculations that previously might have been prohibitively complex or expensive. Modeling of burn injuries fits into this category. This article presents a straightforward method for implementing a finite difference solution to the burn process through the combination of a Macintosh personal computer and a widely used spreadsheet software program; this hardware and software combination has been used widely for a broad spectrum of general computing activities. This article presents a model for a surface thermal burn, as implemented for solution on a spreadsheet, with example runs to illustrate and verify the method.