Click "Calculate" to see the minimum bending radius and the recommended standard tray bend radius (300mm to 900mm) required for safe installation. Tray bend radius must be ≥ minimum cable bend radius. Use the largest cable diameter in the tray for calculation. Always select the next higher standard. How do we calculate the value of radius (R) of the circle in this attached sketch? Basically I am trying to prove that this cable can be pulled in this cable tray without the need of a 90 Deg elbow. So if radius (R) is equal to or greater than 12. A smaller radius. If you have the bend width, radius, straight line extensions at the two ends of the bend, and/or other additional data, you can improve the calculation taking those into account. During installation, cables are bent or flexed in various environmental conditions.