Cable Tray Calculator
Tray, bracket and rod weights together with the bracket count.
Quick answer
With the default inputs: Tray length 50 · Bracket spacing 2 · Tray unit weight 8 kg/m etc.Total tray system weight 511.9 kg
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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.
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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.
How to work it out
- Bracket count n = ⌊total length ÷ spacing⌋ + 1. Horizontal trays run 1.5-2 m apart, vertical trays no more than 2 m.
- Tray weight = length × unit weight × (1 + waste). A 200×100 galvanised trough section is about 6-8 kg/m, 400×150 about 12-16; ladder tray is 20-30% lighter than trough.
- Arm weight = n × arm length × section unit weight × (1 + waste).
- Rod weight = n × rods per bracket × rod length × unit weight × (1 + waste).
- Total the three to get the load, which drives the slab or soffit check, the anchor selection and the material plan.
- Check the cable load too: one YJV 4×95 weighs about 4 kg/m, so ten of them are 40 kg/m — far more than the tray itself, and the hangers must be designed for the total.
Where it goes wrong
- Deriving tray weight from developed area × thickness × 7850. Real tray has stiffeners, covers, splice plates and dividers, making it 30-50% heavier than the theoretical sheet weight. Use the maker's data.
- Setting bracket spacing at 3 m. Cable tray carries heavy power cables, and both the standard drawings and the code call for 1.5-2 m. At 3 m the tray deflects visibly and long spans resonate.
- Leaving out the weight of the cables. Cable often weighs several times the tray, so sizing rods and anchors on tray weight alone is a genuine safety hazard.
- Specifying M8 rods everywhere. Long spans with many circuits need the rods calculated, and the real constraint is usually the anchor's pull-out capacity in concrete rather than the rod's tensile strength.
Material and cost
Galvanised trough tray runs 45-70 CNY/m at 200×100 and 110-160 at 400×150, with powder-coated adding about 20%. Support fabrication and installation is 8-15 CNY/kg. A complete tray system with supports lands around 80-200 CNY/m. Fire stopping and bonding jumpers are normally additional.
On site
- Trays crossing fire walls and floor slabs need fire stopping. It is frequently omitted from the quote and added at handover, when it costs double.
- Keep power and communication trays at least 300 mm apart and fit a metal divider at crossings. Without it you get interference and unexplained packet loss.
- Bond every tray section with at least 4 mm² copper braid and earth the run at two points minimum, meeting the specified resistance.
- Keep fill below 40% for power cables and 50% for control cables — that leaves room for expansion and lets heat escape.
Basis
- GB 50303-2015 Code for acceptance of construction quality of building electrical installation, cable tray installation
- 04D701-3 Standard drawing set, cable tray installation
- GB 50054-2011 Code for design of low voltage distribution, erection of distribution circuits
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.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Cable Tray Calculator. 2026-10-25. https://jianzhujisuan.com/en/cable-tray-support
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.