How to calculate cable tray bends? Calculate the minimum required bend radius by multiplying the cable's outside diameter by its bending factor (e. Then, select a standard tray fitting (300mm, 450mm, etc. ) that matches or exceeds this value. The total tray section consumed = 2 × single bend length. Pre-fab vs Field Bent: For standard offsets (6, 12, 18 in at 45°), use manufacturer pre-fabricated offset fittings to save. Calculate horizontal, vertical, or compound cable tray offsets based on bend angle, offset distance, and available installation space. First multiply the traveling point 120mm by 0. more Simple rules for making cable tray double 90 degree bend.