Use this cable tray sizing calculator to check fill %, select tray size, and comply with IEC 61537 & NEC 392 with formulas, example and checklist. What Is the Standard Size of Cable Tray? What Is. 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. A tray that is too small will overheat and physically damage, and too large tray will drain the project budget.