Cable Pathway Calculator

The fill ratio math models each cable as a circle with area π × (diameter/2)² and multiplies that by cable count, which only works cleanly when all cables share one diameter. If your run mixes Cat6A drops with heavier power whips, running them through this calculator separately (once per cable size) or as distinct pathway calculations gives an accurate combined picture, since simply averaging diameters across a mixed bundle understates the area of the larger cables.

NEC (NFPA 70) Article 392.22 sets 50% as the fill limit for multiconductor power and control cables rated 2000 volts or less in a cable tray, which leaves room for future cable additions and airflow around the bundle. Your jurisdiction, cable class, or a specific tray manufacturer's listing may set a different limit, which is why the maximum fill allowance is an adjustable input rather than a hardcoded constant.

Maximum cables at fill limit is computed by taking your allowed fill percentage of the tray's total cross-sectional area and dividing by one cable's area — it's the absolute ceiling regardless of how many cables you currently have. Remaining capacity subtracts your entered cable count from that ceiling, so it directly tells you how many more cables of the same diameter can still be added before you exceed the fill limit.

No — it simply divides your pathway length by a standard 3-meter tray section length and rounds up, which only estimates straight-run material quantities. It doesn't add extra sections for corner fittings, tees, drop-outs, or vertical risers, so use it as a starting bill-of-materials estimate and add fittings separately based on your actual routing layout.