Heat is generated when current flows through a cable. The ampacity of a cable is the amount of current a cable can carry without exceeding its temperature rating. Accurately estimating ampacity is critical to minimizing the total lifetime cost of a cable installation.

This application implements the Nehers-McGrath equations and cross-checks the results against those tabulated in the National Electrical Code (2017); the good agreement means that this worksheet can be the basis of more complex cable ampacity calculations.