Cable tray load capacity refers to the maximum amount of weight a tray system can safely support across a specified span distance without permanent deformation or structural failure. Load ratings are typically measured in kilograms per meter or pounds per foot. IEC 61537 and IEC 60364 require evaluating tray dimensions based on cable quantity, type, and layout configuration. Wider support spacing increases deflection, so heavier loads require thicker trays, shorter spans, or ladder-type trays. Follow these steps to generate your accurate Bill of Materials (BOM) and engineering report: Step 1: Define. Calculate cable tray fill area, weight loading, and minimum tray width per NEC 392 and NEMA VE 1. Average outside diameter of cables. Inside usable width of the tray. You don't need a PhD—just a consistent method.