Just multiply the internal width of the cable tray by its internal depth. In practice, cable tray dimensions are a system of interrelated measurements —width, depth, length, and material thickness—that directly affect cable fill compliance, heat dissipation, structural loading, and long-term expandability. Save your cable tray sizing calculator results as branded PDF. What Is the Standard Size of Cable Tray? Cable trays come in standardized dimensions based on international regulations like NEC (National Electrical Code) and IEC (International Electrotechnical Commission). It is grounded on 40 years of experience in the manufacturing.