Cable Pathway Calculator

Cable tray and ladder capacity from cable count, diameter, and tray dimensions per NEC Article 392.

Inputs

Number of cables

Cable outer diameter (mm)

Tray width (mm)

Tray depth (mm)

Pathway length (m)

Max fill allowance (%)

Tab to move between fields

Results

Current fill ratio (%)

7.84%

Max cables at fill limit306

Remaining cable capacity258

Total cable area (mm²)2,352.8

Tray area (mm²)30,000

Tray sections needed10

Total cable length (m)1,440

NEC compliant (1=yes)1

How to Use This Calculator

Enter the number of cables and average cable diameter for the pathway.
Set the cable tray or conduit size being considered.
Input the cable fill percentage limit per NEC or TIA standards.
Review whether the pathway is within fill limits and the maximum cables allowed.
Upsize the tray or conduit if fill exceeds 40% for power or 50% for communications cable.

How the result changes with Cable outer diameter (mm)

Cable outer diameter (mm)	Current fill ratio (%)
11	15.21%
36	162.86%
65	530.93%
90	1,017.88%

What each input means

Number of cables: Total cables to route through this tray pathway.
Cable outer diameter (mm): Cable outside diameter in mm. Cat6A ≈ 7.9mm, Cat6 ≈ 6.2mm, power cables 15-25mm.
Tray width (mm): Cable tray width. Common sizes: 150, 300, 450, 600, 900mm.
Tray depth (mm): Tray side rail height / usable depth. Common: 50, 100, 150mm.
Pathway length (m): Total length of the cable tray run in meters.
Max fill allowance (%): Maximum allowed fill per NEC 392. Typically 50% for signal or power cables.

What each result means

Current fill ratio (%): Percentage of tray cross-section occupied by cables.
Max cables at fill limit: Maximum number of cables before exceeding the fill allowance.
Remaining cable capacity: How many more cables can fit within the fill limit.
Total cable area (mm²): Combined cross-sectional area of all cables.
Tray area (mm²): Usable cross-sectional area of the cable tray.
Tray sections needed: Number of standard 3m tray sections for the pathway.
Total cable length (m): Total cable to purchase (cable count × pathway length).
NEC compliant (1=yes): 1 if fill ratio is within allowed limit, 0 if overfilled.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Number of cables = 48, Cable outer diameter (mm) = 7.9, Tray width (mm) = 300, Tray depth (mm) = 100 = 6 input(s) provided
Calculate Current fill ratio
7.84 = 7.84%
Calculate Max cables at fill limit
Max cables at fill limit
306 = 306
Calculate Remaining cable capacity
Remaining cable capacity
258 = 258

Engine last updated August 5, 2026.

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