# Cable Tray Calculator

Tray, bracket and rod weights together with the bracket count.

- Page: https://jianzhujisuan.com/en/cable-tray-support
- Category: M&E (https://jianzhujisuan.com/en/c/me)
- Chinese version: https://jianzhujisuan.com/zh/cable-tray-support.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Tray length 50 m, Bracket spacing 2 m, Tray unit weight 8 kg/m, Arm length per bracket 0.5 m, Arm unit weight 3.77 kg/m, Rod length 1.2 m, Rod unit weight 0.617 kg/m, Rods per bracket 2 pcs, Waste allowance 5%): **Total tray system weight 511.9 kg**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Tray length | number | 50 | m |  |
| Bracket spacing | number | 2 | m | 1.5-2 m on straight runs, plus at bends and joints |
| Tray unit weight | number | 8 | kg/m | 200×100 trough about 8-10, 400×100 about 15-18, cover included |
| Arm length per bracket | number | 0.5 | m | Tray width plus 50-100 mm each side |
| Arm unit weight | number | 3.77 | kg/m | L50×5 3.77, L40×4 2.42, C5 5.44 |
| Rod length | number | 1.2 | m |  |
| Rod unit weight | number | 0.617 | kg/m | φ8 0.395, φ10 0.617, φ12 0.888 |
| Rods per bracket | number | 2 | pcs |  |
| Waste allowance | number | 5 | % |  |

## 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)

## Worked example

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.

## Questions

### 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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Generated by BuildCalc. All calculations run in your browser; no data is uploaded. Formulas follow national standards and common trade practice; local codes govern.