A fundamental quantity that is often required in the layout of PCBs is the the estimation of the current carrying capability of a PCB trace given the thickness of the substrate, the copper thickness ( or weight) and where the layer lies. i.e. an inner layer or an outer layer. Signal Processing Group Inc.’s website has a few posts that examine this from a  empirical point of view. The expression for the current carrying capability of the trace is given in a companion post/paper. In order to facilitate the calculation of the width of the trace a javascript calculator is now being presented. Please visit the SPG website and using the “complimentary items” link download or use this calculator.