Cable tray and ladder fill
Tray or ladder width, tiers, kg/m and the grouping factor.
Reads AS/NZS 3000:2018, Nexans Olex The Handbook:2017, AS/NZS 3008.1.2:2017 (NZ) and AS/NZS 3008.1.1:2017 (AU). Tables checked 1 Oct 2026.
Try a job 4
Each job fills in example values. Replace them with your values.
- Fill a plant room trayTen multicore cables on a perforated tray, with the factor for cable size.
- Lay trefoil submains on a ladderTwo single-core circuits in trefoil, their width and kg/m.
- Find the tiers for ten feedersHow many tiers ten multicore feeders need on a narrow tray.
- Space flat mains on a ladderThree flat circuits spaced on an Australian ladder, with the grouping factor.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Standard
- AS/NZS 3008.1.2 (New Zealand)
- Support
- Perforated tray
- Inside width
- 300 mm
- Width kept free
- 25 %
- Cables
- Multicore (three core and earth)
- Spacing
- Touching
- Cables on the tray
- 2 rows
Tiers needed
1
- Width the cables take
- 125.3mm
- Fill of the fullest tier
- 41.8%
- Cable mass on the heaviest tier
- 4.31kg/m
- Grouping factor to carry to cable size
- 0.73
This result is a design aid. Verify it against the current standard.
Calculation steps
- 4 × 16 mm² multicore, 19.7 mm each78.8mm
- 3 × 6 mm² multicore, 15.5 mm each46.5mm
- Width the cables take125.3mm
- Usable width after a 25 % reserve225mm
- Tiers neededResult1
AS/NZS 3008.1.2:2017 Table 24 Note 5
- Tier 1: 7 cables, 125.3 mm4.31kg/m
Olex Handbook
- Fill of the fullest tier41.8%
- Grouping factor to carry to cable size0.73x
AS/NZS 3008.1.2:2017 Table 24 p.82
About this calculator
How this is calculated
A cable tray or ladder holds cables side by side. AS/NZS 3008.1 rates cables on trays and ladders with grouping factors that hold for one layer of cables on each tier. So the question for a tray is how wide the cables are, laid in one layer, and how many tiers that takes. This tool lays them out and reads the factor.
You pick the cable family and list the sizes and counts. The overall diameters are the cable maker's figures that the conduit fill tool also uses. A multicore cable takes one diameter of width. A single-core three-phase circuit takes two diameters in trefoil and three laid flat. Touching cables sit side by side. Spaced cables have one diameter between them, as Tables 23 and 24 draw, and where sizes differ the tool uses the largest.
The standard sets no fill percentage for a tray, so the width kept free for later cables is yours to choose. The tool places each cable or circuit, in the order you list them, on the first tier with room. A run that does not fit one tier takes another, and stacked tiers are at least 300 mm apart for the factors to hold.
It then reads the grouping factor for the support, the spacing, the tiers used and the most cables or circuits on one tier. A count between two printed columns reads the next column up. Past the printed counts no factor is given. The mass per metre on each tier is the maker's catalogue figure.
| Step | Table or clause | What it decides |
|---|---|---|
| Cable diameters | Olex and Prysmian catalogue diameters | The width each cable or circuit takes |
| Spacing | AS/NZS 3008.1 Tables 23 and 24 Note 1 | One diameter between spaced cables or circuits |
| One layer per tier | AS/NZS 3008.1 Tables 23 and 24 Note 5 | The tiers the run needs |
| Tier spacing | AS/NZS 3008.1 Tables 23 and 24 Note 6 | The gap between stacked tiers |
| Grouping factor | AS/NZS 3008.1 Table 23 or Table 24 | The factor to carry to the cable size |
| Mass | Olex Handbook mass per metre | The kg/m on each tier |
Worked examples
- A plant room tray: four 16 mm² and three 6 mm² multicore cables fit on 1 tier of a 300 mm perforated tray. They take 125.3 mm, a grouping factor of 0.73.
- Two 95 mm² trefoil submains on a 450 mm ladder fit on 1 tier, 60.8 mm wide, with a grouping factor of 0.95.
- Ten 35 mm² multicore feeders on a 300 mm tray need 2 tiers with a quarter of the width kept free. The fullest tier carries nine cables, a grouping factor of 0.68.
- Three flat 240 mm² circuits spaced on a 600 mm Australian ladder fit on 1 tier at a grouping factor of 1.
Limits
The tool lays one cable family at a time: multicore three core and earth cables, or single-core three-phase circuits. It does not mix the two, model cables in more than one layer, or check segregation between services on the same tray. Use the segregation tool for that.
Single-core widths use the diameter of unsheathed V-90 single cores, the conduit fill figures. A sheathed or XLPE single core is wider, so allow for it. The mass is the cable alone. Check the tray or ladder against its maker's load and span tables, with the fixings and any future cables.
See also: Cable size, Correction factors and Conduit fill.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
Is there a maximum fill for a cable tray?
AS/NZS 3008.1 sets no fill percentage for a tray or ladder. Its grouping factors assume one layer of cables on each tier. The tool lays one layer and keeps the reserve you choose for later cables.
What does spaced mean on a tray?
Spaced cables have one cable diameter between them, as AS/NZS 3008.1 Tables 23 and 24 draw. Where the sizes differ the tool uses the largest diameter. Spacing raises the grouping factor and takes more width.
How wide is a trefoil circuit?
Three single-core cables in trefoil sit two diameters wide on the tray. Laid flat they take three diameters. The tool uses the overall diameter from the cable maker's catalogue.
What grouping factor do I use for cable size?
The tool reads AS/NZS 3008.1 Table 23 for single-core circuits or Table 24 for multicore cables, at the tiers it used and the most cables on a tier. Carry that factor into the cable size tool.
Does it check the tray can carry the weight?
No. It gives the kg/m of cable on each tier from the maker's catalogue. Check that against the tray maker's load and span tables.
Clauses and tables this tool reads
- AS/NZS 5000.1 cables, manufacturer dataCable overall diameters
- AS/NZS 3008.1.2:2017 Table 23Grouping factors for single-core circuits on trays, ladder supports, racks and cleats in air
- AS/NZS 3008.1.2:2017 Table 24Grouping factors for multicore cables on trays, ladder supports, racks and cleats in air
- AS/NZS 3008.1.1:2017 Table 23Grouping factors for single-core circuits on trays, ladder supports, racks and cleats in air
- AS/NZS 3008.1.1:2017 Table 24Grouping factors for multicore cables on trays, ladder supports, racks and cleats in air
- cable-massApproximate cable mass per metre
Every clause and table, with how each was verified
Tables last checked on 1 Oct 2026.
Related tools
- Cable size calculatorFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Conduit fill calculatorCheck that a cable bundle fits in a conduit.AS/NZS 3008.1.2AS/NZS 3000
- Correction factor calculatorRead each correction factor and the rating a cable needs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
Was this useful?
A question, or a value that looks wrong? Contact us.