Check how much conduit space the selected cables occupy.
AS/NZS 3000 Paragraph C6.2 space factors (0.5 for one cable, 0.33 for two, 0.4 for three or more) with indicative cable and conduit dimensions. Circular cable needs manufacturer diameters. Long runs, bends and grouping are not modelled.
Results
Enter cable sizes and conduit size, then calculate.
Method and assumptions
AS/NZS 3000:2018 Paragraph C6.2: the total cross-sectional area of the cables must not exceed the conduit's internal area multiplied by the space factor: 0.5 for one cable, 0.33 for two, 0.4 for three or more.
Built-in outside diameters and bores are indicative typical values. Tables C10 to C12 apply the method to common cable and conduit types and are the guide to check against.
The method assumes a short, clear run with few bends. Reduce the number of cables for long runs or several bends, and allow for grouping derating under AS/NZS 3008.
Common questions
How is conduit fill worked out?
With Paragraph C6.2 of AS/NZS 3000:2018: the total cross-sectional area of the cables must not exceed the internal area of the conduit multiplied by a space factor of 0.5 for one cable, 0.33 for two cables, or 0.4 for three or more.
Why is the limit lower for two cables?
Two round cables leave more unusable space in a round conduit than three or more, so Paragraph C6.2 uses a space factor of 0.33 for two cables instead of 0.4.
Which cable and conduit dimensions does it use?
Built-in diameters are indicative typical values for flat two-core and earth cable and unsheathed building wire. Circular multicore cable needs manufacturer outside diameters. AS/NZS 3000 Tables C10 to C12 apply the same method to common cable and conduit types; check against them or enter manufacturer dimensions.
Does the result allow for long runs and bends?
No. The method assumes a short run that is clear of obstructions with few bends. Reduce the number of cables for long runs or several bends, keep within the cable’s pulling tension and bending radius, and apply AS/NZS 3008 grouping factors separately.
