Free cable tray fill calculator to estimate tray fill percentage by tray width/depth and cable diameter/count. Includes a planning pass/high indicator. 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. Calculate cable tray fill ratio, weight loading, and derating factors for multi-standard compliance. Enter your cable schedule below to get started. Additional engineering factors must be considered to ensure safety, reliability. Determine the total usable cross-sectional area of the cable tray by multiplying its width by its height (or depth).