How do I choose cable tray width for Australian electrical installations?

Sum the outer diameter of every cable to be installed, allowing for AS/NZS 3008.1.1:2025 spacing if your design requires grouping derating relief, add a future-capacity reserve (commonly 20–50%), then select the smallest standard tray nominal width (50, 75, 100, 150, 225, 300, 450, 600, 750 or 900 mm) that fits the result. The ElecAS cable tray sizing calculator does this automatically using real Prysmian and Olex catalogue data.

How do I calculate trefoil cable tray width?

A touching trefoil group of three identical single-core cables of diameter D occupies a tray width of 2D (the bounding rectangle of an equilateral triangle of side D). For spaced trefoil groups, add the spacing factor multiplied by D between groups. The ElecAS cable tray sizing calculator groups three matching single-cores into trefoil automatically when the trefoil layout method is selected.

Should cables on a tray be touching or spaced?

Touching arrangements use less tray width but trigger AS/NZS 3008.1.1:2025 Table 22 / 23 grouping derating, forcing larger conductor sizes. Spacing cables by at least one diameter (per Tables 25–27) eliminates most of the derating but uses more tray width. The right trade-off depends on load currents, available real estate and cable cost. For sub-mains carrying near-rated currents, spacing is usually worth the extra tray width.

Does cable tray sizing have a load weight limit?

AS/NZS 3000:2018 does not publish numeric tray load limits. Every tray manufacturer (EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil) publishes safe working load curves based on support span — typically 25 kg/m at 3 m span for medium-duty perforated tray, up to 200 kg/m at 1.5 m span for heavy-duty ladder. The ElecAS calculator outputs cable mass per metre per tier so the responsible engineer can cross-check against the chosen tray product.

What reserve capacity should I use for cable tray sizing in Australia?

Industry practice is 25–50% reserve for greenfield commercial fit-outs, 20% for tight retrofits and infrastructure, and 50–100% for mission-critical installations (data centres, hospitals, defence). The ElecAS calculator defaults to 20% but accepts any value from 0% to 100%. Set the reserve before sizing — it directly drives the recommended tray width.

Can I mix flat and trefoil cables on the same tray?

Yes. The ElecAS cable tray calculator handles per-cable layout choice — three single-cores in trefoil for the heavy submain, flat-touching multicore for the lighting circuits, all on the same tier. Each cable contributes its calculated width (trefoil = 2D, flat = D, plus spacing) and the calculator packs them sequentially.

What tray width do I need for 4 × 25 mm² 4-core-and-earth XLPE armoured cables?

Four touching SWA armoured 4C+E XLPE 25 mm² Cu multicores at ~28.3 mm outer diameter each require approximately 113 mm raw width. With 20% reserve that becomes 136 mm, recommending a 150 mm wide tray. Four unarmoured equivalents at ~23 mm OD would need 92 mm raw, 110 mm with reserve, fitting on a 150 mm tray as well — but a 100 mm tray would also work if the reserve is dropped to 8%.

Does the ElecAS calculator support ladder, perforated and solid-bottom trays?

The calculator outputs tray width nominal which applies to ladder, perforated and solid-bottom trays — the geometric fill is the same. Depth, ventilation and current-rating implications differ between tray types (solid-bottom trays have reduced AS/NZS 3008.1.1 current ratings relative to perforated and ladder). The responsible engineer should confirm the chosen tray type against AS/NZS 3008.1.1 installation method tables.

Is this cable tray sizing calculator free?

Yes. The full cable tray sizing calculator is free to use online with no sign-up required. Branded PDF reports with company logo, designer name and accent colour are included in the free tier. Cloud project sync and team workspaces are paid Pro / Team features.

ElecAS

Cable Tray Sizing Calculator

Why this page matters

Free Australian cable tray sizing calculator. Pick from real Prysmian and Olex cable catalogue data, choose flat or trefoil arrangements, touching or spaced layouts, and get the smallest compliant tray with tier allocation and a branded PDF report. This static content is published so the canonical route has meaningful crawlable HTML even before the interactive application hydrates.

Who this page is for

Electrical engineers, designers, contractors and project drafters sizing ladder and perforated cable trays for AS/NZS 3000:2018 installations, sub-mains and mains cable runs in industrial, commercial and infrastructure projects across Australia and New Zealand.

Relevant standards

AS/NZS 3000:2018 — Electrical installations (Wiring Rules), wiring systems
AS/NZS 3008.1.1:2025 — Electrical installations, selection of cables, Tables 22–24 (grouping factors) and Tables 25–27 (touching vs spaced arrangements)
AS/NZS 5000.1 — Electric cables — Polymeric insulated, voltages up to and including 0.6/1 kV
IEC 60364-5-52 — Selection and erection of wiring systems (cable management)
Manufacturer tray load curves (e.g. EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil) for span-based safe working load

What this tool helps with

Pick from 380+ Prysmian Australia and Olex (Prysmian Group) cable products with manufacturer-published outer diameter and mass — no hand-typed approximations.
Flat (touching), flat (spaced), trefoil (touching) and trefoil (spaced) layouts on a per-cable basis — mix arrangements within the same tray.
Trefoil width = 2 × cable diameter geometry, with automatic grouping of three matching single-core cables per circuit.
Reserve capacity allowance (default 20%) applied per-tier so each tier preserves spare room for future cables.
Multi-tier allocation when the smallest tray cannot fit the bundle — packs cables into stacked tiers up to the user-defined maximum tray width.
Cable mass in kg/m per tier so designers can cross-check against tray manufacturer span-load curves (EzyStrut, Unistrut, Legrand Cablofil, Cooper B-Line).
Standard nominal widths: 50, 75, 100, 150, 225, 300, 450, 600, 750 and 900 mm — the common Australian tray product ladder.
Branded PDF report with cable schedule, tier allocation and to-scale cross-section, with manufacturer catalogue references embedded for procurement.

How to size a cable tray for AS/NZS 3000:2018

Pick the cable manufacturer — Filter the catalogue to Prysmian Australia or Olex (Prysmian Group). The mass per metre and outer diameter feed both the width calculation and the tray-load weight estimate.
Choose a cable family — Select the construction family for each cable on the tray. SWA armoured cables, SDI single-core and flex variants all have different outer diameters and masses; the calculator applies the right values automatically.
Pick the layout method per cable — Flat (touching) packs cables shoulder-to-shoulder, flat (spaced) adds a configurable diameter gap, trefoil (touching) groups three matching single-cores into an equilateral triangle of width 2D, and trefoil (spaced) adds a gap between trefoil groups.
Set the spacing factor for spaced layouts — For AS/NZS 3008.1.1:2025 Tables 25–27 derating relief, spacing must be at least one cable diameter. Set spacingFactor = 1.0 for touching avoidance, or 2.0–3.0 if your specification requires more.
Set reserve capacity and maximum tray width — Reserve is the future-cable allowance (commonly 20–50% in industrial fit-outs). The maximum tray width caps the largest single tier the calculator may select; beyond that limit the calculator stacks tiers.
Review the recommendation and export the PDF — The output shows recommended tray nominal width, tier count, mass per metre, used width and a cross-section sketch. Export the PDF for the design pack; cross-check the mass against the tray vendor span-load curve.

Complete guide to cable tray sizing for AS/NZS 3000:2018 projects

Geometry — why flat and trefoil arrangements have different tray widths

Three identical single-core cables of diameter D packed in a touching trefoil form an equilateral triangle of side D. The bounding rectangle is 2D wide and (D + D × √3/2) ≈ 1.87D tall. The calculator therefore consumes 2D of tray width per trefoil group, versus 3D of tray width if the same three cables were laid flat and touching. Trefoil reduces tray width but increases tray depth requirement.

For spaced arrangements, an additional gap of one or more cable diameters between adjacent cables (or between trefoil groups) is required to obtain AS/NZS 3008.1.1:2025 Table 26 grouping factor relief. Spacing of 1D between flat cables typically restores 80–90% of the ungrouped current rating; spacing of 2D essentially eliminates grouping derating.

AS/NZS 3008.1.1 grouping derating and tray-layout decisions

Cables laid touching in a single layer on a tray are derated under AS/NZS 3008.1.1:2025 Table 22 (multi-core) or Table 23 (single-core). The derating factor drops from 1.00 for a single circuit to around 0.85 for three circuits and 0.70 for six or more circuits in the same touching layer.

Tables 25–27 then offer relief when cables are spaced — by at least one cable diameter for adjacent single-core, or one trefoil width for trefoil groups. The trade-off is direct: spaced layouts use more tray width but allow smaller cable sizes (less derating), and touching layouts use less tray width but force larger cables (more derating). The ElecAS calculator handles the geometry side; the ElecAS cable selection calculator handles the current-rating side.

Reserve capacity — what value to pick

Industry practice for greenfield commercial fit-outs in Australia is 25–50% reserve capacity on cable trays, with 20% common for tight retrofit and infrastructure projects. Reserve allows for future cable adds without re-trunking the building. The ElecAS calculator applies reserve as a per-tier multiplier on usable width, so each populated tier preserves the same reserve fraction.

For mission-critical installations (data centres, hospitals, defence) clients frequently mandate 100% reserve or N+1 redundancy. Set the reserve field accordingly and use the maximum tray width limit to cap the largest single tier; the calculator will stack tiers if the bundle exceeds that cap.

Tray load — cable mass per metre and tray span

The calculator reads cable mass per 100 m directly from the Prysmian and Olex catalogues and converts to kg/m for each tier. Compare the tier mass against the tray manufacturer span-load curve — typical perforated tray ratings range from 25 kg/m at 3 m support span to 75 kg/m at 1.5 m, with heavy-duty ladder trays reaching 200 kg/m at short spans.

AS/NZS 3000:2018 does not publish numeric tray load limits — those come from the tray vendor (EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil). The ElecAS PDF includes total mass per metre and per-tier mass so the responsible engineer can perform the vendor check.

Standard cable tray sizes in Australia

Cable tray products from Australian distributors typically follow the 50, 75, 100, 150, 225, 300, 450, 600, 750 and 900 mm nominal width ladder. The calculator selects the smallest tray whose actual width accommodates the raw cable bundle plus reserve. Trays wider than 900 mm exist (e.g. 1200 mm splitable into two 600 mm trays) but are uncommon outside utility and substation environments.

Depth nominally 50 mm for light-duty perforated tray; 75–100 mm for medium-duty ladder; 150 mm and above for heavy-duty cable ladder carrying high-voltage cables. The calculator outputs width only — depth selection follows the largest cable OD and the chosen layout (trefoil bundles need more depth than flat formations).

When to use cable tray, conduit or ladder

Cable tray (perforated and ladder) is preferred for sub-mains, mains and submains feeders inside plant rooms, risers and ceiling spaces where pulling tolerance, future modification and ventilation matter more than mechanical protection. Conduit (HD-PVC, medium-duty) is preferred for final subcircuits and exposed runs where mechanical protection, water ingress and aesthetics dominate.

For mixed installations — tray on the riser, conduit on the floor — the ElecAS conduit sizing calculator and cable tray sizing calculator share the same Prysmian and Olex catalogue so cable picks remain consistent across both reports.

Reviewed by

Wisam Tozah — Associate Electrical Engineer. B.Eng (Electrical), MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus). LinkedIn.

Frequently asked questions

How do I choose cable tray width for Australian electrical installations?: Sum the outer diameter of every cable to be installed, allowing for AS/NZS 3008.1.1:2025 spacing if your design requires grouping derating relief, add a future-capacity reserve (commonly 20–50%), then select the smallest standard tray nominal width (50, 75, 100, 150, 225, 300, 450, 600, 750 or 900 mm) that fits the result. The ElecAS cable tray sizing calculator does this automatically using real Prysmian and Olex catalogue data.
How do I calculate trefoil cable tray width?: A touching trefoil group of three identical single-core cables of diameter D occupies a tray width of 2D (the bounding rectangle of an equilateral triangle of side D). For spaced trefoil groups, add the spacing factor multiplied by D between groups. The ElecAS cable tray sizing calculator groups three matching single-cores into trefoil automatically when the trefoil layout method is selected.
Should cables on a tray be touching or spaced?: Touching arrangements use less tray width but trigger AS/NZS 3008.1.1:2025 Table 22 / 23 grouping derating, forcing larger conductor sizes. Spacing cables by at least one diameter (per Tables 25–27) eliminates most of the derating but uses more tray width. The right trade-off depends on load currents, available real estate and cable cost. For sub-mains carrying near-rated currents, spacing is usually worth the extra tray width.
Does cable tray sizing have a load weight limit?: AS/NZS 3000:2018 does not publish numeric tray load limits. Every tray manufacturer (EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil) publishes safe working load curves based on support span — typically 25 kg/m at 3 m span for medium-duty perforated tray, up to 200 kg/m at 1.5 m span for heavy-duty ladder. The ElecAS calculator outputs cable mass per metre per tier so the responsible engineer can cross-check against the chosen tray product.
What reserve capacity should I use for cable tray sizing in Australia?: Industry practice is 25–50% reserve for greenfield commercial fit-outs, 20% for tight retrofits and infrastructure, and 50–100% for mission-critical installations (data centres, hospitals, defence). The ElecAS calculator defaults to 20% but accepts any value from 0% to 100%. Set the reserve before sizing — it directly drives the recommended tray width.
Can I mix flat and trefoil cables on the same tray?: Yes. The ElecAS cable tray calculator handles per-cable layout choice — three single-cores in trefoil for the heavy submain, flat-touching multicore for the lighting circuits, all on the same tier. Each cable contributes its calculated width (trefoil = 2D, flat = D, plus spacing) and the calculator packs them sequentially.
What tray width do I need for 4 × 25 mm² 4-core-and-earth XLPE armoured cables?: Four touching SWA armoured 4C+E XLPE 25 mm² Cu multicores at ~28.3 mm outer diameter each require approximately 113 mm raw width. With 20% reserve that becomes 136 mm, recommending a 150 mm wide tray. Four unarmoured equivalents at ~23 mm OD would need 92 mm raw, 110 mm with reserve, fitting on a 150 mm tray as well — but a 100 mm tray would also work if the reserve is dropped to 8%.
Does the ElecAS calculator support ladder, perforated and solid-bottom trays?: The calculator outputs tray width nominal which applies to ladder, perforated and solid-bottom trays — the geometric fill is the same. Depth, ventilation and current-rating implications differ between tray types (solid-bottom trays have reduced AS/NZS 3008.1.1 current ratings relative to perforated and ladder). The responsible engineer should confirm the chosen tray type against AS/NZS 3008.1.1 installation method tables.
Is this cable tray sizing calculator free?: Yes. The full cable tray sizing calculator is free to use online with no sign-up required. Branded PDF reports with company logo, designer name and accent colour are included in the free tier. Cloud project sync and team workspaces are paid Pro / Team features.