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. How to calculate. How to bend 22. How to bend 90 degree of cable tray 3 line with the same distance :// • HOW TO BEND 90 DEGREE OF CABLE TRAY 3 LINE. Always select the next higher standard. In the attached sketch, the width of the cable tray is 12". Use this tool to estimate sloped section length, horizontal run requirement, cut marks, and installation feasibility.