Cable Tray & Conduit Calculator
Lengths, fittings, fixings, and cost - for cable tray, conduit, trunking, and cable basket.
System settings
Select the width / diameter of your system.
Standard section lengths: conduit 3 m, tray 3 m, trunking 2-3 m.
Typically 10% for offcuts and bends.
Conduit: 0.5-1 m. Cable tray: 1-1.5 m. Basket tray: 1-2 m.
Fittings per run (enter count, or leave 0)
Leave blank to auto-calculate from run lengths.
Runs / routes
Job Costing (optional)
UK Market PricesFills in the material cost fields with current UK market prices. You can review and edit each price before applying.
Results
Total run length
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m (inc. waste)
Sections to buy
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3 m lengths
Fixings needed
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supports / brackets
Run breakdown
| Run / route | Net length (m) | With waste (m) | Sections | Fixings |
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Fittings summary
| Item | Quantity |
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Frequently Asked Questions
What is the difference between cable tray, cable trunking, and conduit?
Cable tray: open-bottomed ladder or perforated channel - supports cables in bulk in commercial/industrial installations; cables remain accessible. Cable trunking: enclosed rectangular duct with removable lid - mechanical protection and neat appearance for offices and corridors. Conduit: tube through which cables are pulled - maximum mechanical protection for exposed, high-risk, or external locations.
What cable tray size do I need?
Calculate total cross-sectional area of all cables and select a tray width giving a cable fill ratio of no more than 40-45% (allows heat dissipation and future additions). Standard widths: 50, 75, 100, 150, 225, 300, 450, 600 mm. For high-voltage or data cables: check the manufacturer's derating tables as cable bunching can require current-carrying capacity derating.
What support spacing do I need for cable tray?
Steel cable tray: 1.5-2.0 m centres for trays up to 300 mm wide; 1.0-1.5 m centres for 450-600 mm trays under heavy loading. GRP trays: requires more frequent support - check manufacturer's load tables. Add additional supports close to each fitting (bends, tees). Follow the IET Wiring Regulations (BS 7671) for cable support spacing requirements.
What conduit size do I need for my cables?
Use the cable fill tables in the IET On-Site Guide (Appendix C) or BS EN 61386. Cable fill must not exceed 45% of conduit internal cross-sectional area for 3+ cables (40% at bends). Standard sizes: 16, 20, 25, 32, 40, 50 mm internal diameter. Single cable: conduit internal diameter at least 1.5x the cable outer diameter.
Do I need steel or plastic conduit?
Steel conduit: highest mechanical protection - required in industrial environments, external locations, or where impact/fire risk exists. Also provides earth continuity if correctly jointed. PVC conduit: lighter, corrosion-resistant, non-conductive - suitable for most domestic and light commercial use concealed in walls/ceilings. Flexible conduit: for final connections to motors or equipment with vibration. All conduit must comply with BS 7671.
How much waste should I allow when ordering cable tray or conduit?
Straight runs with moderate fittings: 10% waste. Complex installations with many bends and tees: 15%. Cable tray and steel conduit: sold in 3 m lengths; PVC conduit also in 3 m lengths. Count all fittings separately (bends, tees, couplers, reducers, end caps) - they are not included in the straight length calculation. For trunking: measure each run separately and include all angles and tee pieces.