Cable Tray Calculator
Tray, bracket and rod weights together with the bracket count.
Quick answer
With the default inputs: Tray length 50 m · Bracket spacing 2 m · Tray unit weight 8 kg/m etc.Total tray system weight 511.9 kg
Edit the inputs below to recalculate.Inputs
Result
Total tray system weight
511.9kg
| Bracket count | 26pcs |
| Tray weight | 420.0kg |
| Bracket steel weight | 51.46kg |
| Total rod length | 62.4m |
| Rod weight | 40.43kg |
| Anchors required | 52sets |
| Weight per metre | 10.24kg/m |
| Bracket share of total | 18.0% |
Bracket count follows spans plus one — both ends of a run need support. Bends, tees, reducers and expansion joints each need an extra bracket either side; add those from the drawing. For multi-layer tray (power, data, fire alarm stacked) calculate brackets per layer but share posts and rods, or simply multiply rods and arm length by the number of layers here.
Formula
| Bracket count | n = ⌊length ÷ spacing⌋ + 1 |
| Tray weight | W = length × unit weight × (1 + waste) |
| Bracket steel weight | W = n × arm length × unit weight × (1 + waste) |
| Rod weight | W = n × rods per bracket × rod length × unit weight × (1 + waste) |
50 m of tray at 8 kg/m with 2 m spacing, 0.5 m L50×5 arms and two 1.2 m φ10 rods: 26 brackets, 420 kg tray, 51.46 kg steel, 40.43 kg rod — 511.9 kg total, 10.2 kg/m.
FAQ
Why are tray brackets closer than duct hangers?
Tray plus cables forms a heavy line load and the tray itself is thin sheet that sags over long spans. Code calls for 1.5-2 m horizontally and no more than 2 m vertically (1.5 m in some regions), with extra brackets at bends, joints and cabinet entries. Confirm the manufacturer's allowable span when using 2 m — light-gauge tray may only permit 1.5 m.
Does the tray need bonding jumpers?
Yes. The metal tray system must be reliably earthed and electrically continuous over its full length. Non-galvanised tray needs copper jumpers of at least 4 mm² between sections; galvanised tray with two or more bolted connections per joint using locknuts or spring washers may omit the jumper but must still be earthed. Connect the system to the protective earth main at two points minimum — inspectors check this.
How full can a tray be?
Fill ratio should not exceed 40% for power cables or 50% for control cables, with room left for future additions. Work it out as the sum of cable cross-sections over the tray's internal area. Crowding a 400 mm tray for economy degrades heat dissipation and derates the cables, and leaves no way to pull or replace them — size from the final cable schedule, not from what is being pulled today.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.