Cable Tray Support Span Calculator

Method & Assumptions

Maximum support span is governed by the L/100 deflection limit defined in NEMA VE 1-2017 §4. For a uniformly distributed cable load on a simple span, midpoint deflection is:

δ = 5wL⁴ / (384EI)  ≤  L/100

Normalising against the tray's rated conditions at the class test span gives:

max_span = L_rated × (w_rated / w_actual)^(1/3)

Variables:

  • w_actual — total cable weight per linear foot of tray (lbs/ft)
  • w_rated — NEMA load-class working load (lbs/ft)
  • L_rated — class test span (12 ft for all standard classes)

Citations: NEMA VE 1-2017

Applicability: aluminum and steel ladder trays, solid-bottom trays, and wire-mesh trays with standard NEMA load classes. Fiberglass trays (NEMA FG 1) use identical load-class designations and the same formula.

See also: Cable Tray Fill, Raceway Schedule.

Tray Load Class

Select the load class stamped on the tray or specified by the manufacturer. Class 16A (16 lbs/ft, 12 ft span) is typical for industrial installations.

Input Mode
Cable List

Add cables below and the total weight per foot will be computed automatically, or type a value directly in the field beneath the table.

Conductors Conductor Size Quantity Weight (lbs/ft) Remove
Total Cable Weight

Summed automatically from the cable list above, or enter a value manually. Include all cables sharing this tray section.