What is the standard size of cable tray? Standard cable tray sizes range from 50mm to 600mm in width. Common widths include 100mm, 200mm, 300mm, and 450mm. How do I calculate cable. 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. Here in the UK, standard widths run from a slim 50mm for a handful of data runs right up to 900mm or more for the heavy-duty. Selecting the appropriate electrical cable tray dimensions is a critical decision that directly impacts the safety, efficiency, and longevity of any industrial or commercial electrical installation. The three main types are ladder tray, perforated.