Site cord length calculator
The longest a cord or cable may run on a construction site.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Rated current
- 10 A
- Conductor area
- 2.5 mm²
- Cable
- Single phase, 3 core
- Use
- General use, such as saws, grinders and drills
- Total length from the socket-outlet to the equipment
- 40 m
- PSOA supply lead
- 0 m
- Voltage drop the fixed wiring uses before the socket-outlet
- 0 %
- Two or more cord extension sets are joined
- No
- The cord is used coiled or on a reel
- No
Maximum length
60m
- Length checked
- 40m
- PSOA supply lead
- 0m
- Inside the limit
- Yes
- Voltage drop the length is based on
- 5%
- Voltage drop already used upstream
- 0%
- Total voltage drop at the equipment
- 5%
- Reference
- AS/NZS 3012:2010 Table 1
This result is a design aid. Verify it against the current standard.
Calculation steps
- Length entered40mAS/NZS 3012:2010 Table 1
- PSOA supply lead0mAS/NZS 3012:2010 Cl 2.6.10 Note 2
- Length checked against Table 140mAS/NZS 3012:2010 Table 1
- Rated current10AAS/NZS 3012:2010 Table 1
- Conductor area2.5mm²AS/NZS 3012:2010 Table 1
- Voltage drop the length is based on5%AS/NZS 3012:2010 Table 1
- Voltage drop already used upstream0%AS/NZS 3012:2010 Table 1
- Total voltage drop this length implies5%AS/NZS 3012:2010 Table 1
- Maximum length60mAS/NZS 3012:2010 Table 1
- General use, single phase60mAS/NZS 3012:2010 Table 1
- General use, three phase120mAS/NZS 3012:2010 Table 1
- Specific use, single phase35mAS/NZS 3012:2010 Table 1
- Specific use, three phase70mAS/NZS 3012:2010 Table 1
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
How long can an extension cord run on a construction site?
Table 1 of AS/NZS 3012:2010 gives a limit for each rated current and conductor size. A 10 A, 2.5 mm² single phase cord for general use stops at 60 m. The three phase, four core cable of that size reaches 120 m.
What is the difference between general use and specific use?
General use covers everyday site tools such as saws, grinders and drills. Its lengths allow a 5 percent drop at the rated current. Specific use is for equipment where a failed motor start puts someone at risk. Its lengths allow 3 percent, so they are shorter.
Does the table's voltage drop include the fixed wiring?
No. The table's percentage adds to the drop the fixed wiring already uses before the socket-outlet. Enter that figure, and the tool shows the total at the equipment. Every result says so.
Can I join two extension leads together?
Yes, if the whole run stays inside one Table 1 limit. Enter the total of every joined set, and the tool checks that sum. A PSOA supply lead counts too, so the tool adds it. AS/NZS 3012 recommends a single set, and says not to use a cord coiled or on a reel.
What is the smallest cord conductor allowed?
Cl 2.6.2 sets 1.0 mm² as the floor for each core of a flexible cord. The cord also needs an earth conductor beside its live conductors.