While they offer a versatile and efficient way to manage complex wiring, calculating conductor ampacity within them is more nuanced than for conductors in conduit. The definitive guide for these calculations is Article 392, with section 392. 80 providing the specific ampacity. Determine the total usable cross-sectional area of the cable tray by multiplying its width by its height (or depth). For mixed cables, sum the areas of all individual cables. Follow these simple steps: Define Tray Dimensions: Enter the width and depth of your planned cable tray (in mm or inches). Select Fill Standard: Choose 40% for power cables (NEC compliant) or 50% for. A Cable Tray Capacity Calculator is an essential tool for electrical engineers, contractors, and project managers involved in the installation and management of electrical cables.