Cable tray support quantity can be calculated using a simple formula: Support Quantity = Total Length ÷ Support Spacing + 1 20 ÷ 2 + 1 = 11 supports In a typical project, a 20-meter cable tray with 2-meter spacing requires 11 supports. As a key structure supporting the cable tray, the accurate calculation of the support quantity directly affects construction costs, efficiency, and safety. In complex engineering environments, the. Properly sizing your cable tray is critical for safety and compliance. Select Fill. Hubbell Take Off Support provides the contractor, engineer, end user a completed BOM, including all related products, counts, symbol legends and information required to price a project. 5 inches, in a 4-inch deep cable tray.