Cable size calculator
Libreng cable size calculator para sa New Zealand at Australia. Binabasa nito ang AS/NZS 3008.1.2:2017, o ang AS/NZS 3008.1.1:2025 na may pagpipiliang 2017, at tinitingnan ang AS/NZS 3000.
Reads AS/NZS 3008.1.2:2017 (NZ), AS/NZS 3008.1.1:2017 and 2025 (AU) and AS/NZS 3000:2018. Tables checked 27 Sept 2026.
Subukan ang isang job 24
Nilalagyan ng halimbawang value ang bawat job. Palitan ang mga ito ng sarili mong value.
- Size a cable for a shedThe smallest cable that carries the load over the run to a shed.
- Size a cable for an EV chargerThe cable size for a 32 A charger on a 25 m run.
- Size a submain for a tenancyThe smallest three phase submain that passes each check, on AU 3008.1.1:2025.
- Price a cable runA size and a length you can take to a price.
- Size the cable for an ovenThe cable for a 32 A cooking circuit on a 15 m run.
- Size a hot water cylinder circuitThe cable for a 3 kW cylinder on a 20 m run.
- Size a heat pump circuitThe cable for a 20 A heat pump on an 18 m run.
- Size the mains for a houseThe consumer mains for 63 A over 25 m underground.
- Size a three‑phase EV charger circuitThe cable for a 22 kW charger on a 30 m run.
- Size an aluminium submainThe smallest aluminium submain for 250 A over 80 m.
- Size a cable in ceiling insulationThe cable for 16 A where insulation surrounds it.
- Size a cable on a hot roofThe cable for 25 A at 50 °C ambient.
- Size a buried cable in dry soilThe cable for 100 A at 2.5 K·m/W and 0.8 m deep.
- Size six circuits on one trayThe cable for 40 A grouped with five other circuits.
- Size parallel cables for 800 ATwo cables per phase for an 800 A feeder.
- Size a cable for a harmonic loadThe cable for 63 A with 35 % third harmonic.
- Size a 22 kW motor cableThe cable for a 41 A motor over 60 m on a 50 A D‑curve breaker.
- Size a submain to a sleep-outThe submain for 40 A over 35 m.
- Size a cable with a fault checkThe cable for 32 A that also withstands 6 kA for 0.1 s.
- Size a pool pump circuitThe cable for a 1.5 kW pump on a 30 m run.
- Size a welder outlet circuitThe cable for a 32 A three‑phase outlet in a workshop.
- Size a workshop submainThe three‑phase submain for 63 A over 45 m.
- Size a supply to a tiny homeThe cable for a 16 A supply over 30 m.
- Size a submain to the 2025 editionA 100 A run of 50 m, read on AS/NZS 3008.1.1:2025 for Australia.
Mga input
Worked example gamit ang mga default na input.
- Mga phase
- Three phase
- Voltage
- 400 V
- Design current
- 50 A
- Power factor
- 0.9
- Standard
- NZ · AS/NZS 3008.1.2
- Haba ng run
- 60 m
- Installation method
- Enclosed sa hangin
- Ambient na temperatura
- 30 °C
- Naka-group na circuit
- 1
- Third harmonic content
- 0 %
- Material
- Tanso
- Insulation
- PVC 75 °C
- Mga core
- Multicore
- Mga cable na parallel
- 1
- Limit ng voltage drop
- 5 %
- Suriin ang protective device
- Hindi
- Prospective fault current
- 0 kA
Laki ng conductor
10mm²
- Derated na kapasidad
- 50A
- Voltage drop
- 2.66%
- Earth conductor
- 4mm²
- Kabuuang derating factor
- 1.00
Design aid lang ang resultang ito. I-verify ito laban sa kasalukuyang standard.
Mga hakbang ng kalkulasyon
- Ambient derating factor×1.00
AS/NZS 3008.1.2:2017 Tables 27(1), 27(2) p.88
- Grouping derating factor×1.00
One circuit, no grouping factor
- Soil derating factor×1.00
AS/NZS 3008.1.2:2017 Table 29 p.90
- Derating factor ng lalim ng paglilibing×1.00
AS/NZS 3008.1.2:2017 Tables 28(1), 28(2) p.89
- Total derating factor×1.00
- Kinakailangang tabulated current50A
AS/NZS 3000:2018 Cl 3.4
- Napiling laki ng conductorResulta10mm²
AS/NZS 3008.1.2:2017 Table 13 p.62–64
- Derated na current capacity50A
AS/NZS 3000:2018 Cl 3.4
- Voltage drop2.66%
Tungkol sa calculator na ito
How this is calculated
The tool tests every standard conductor size in turn. It reports the smallest size that passes each check you ask for.
- Tabulated current. It reads the current each size can carry for your material, insulation, core count and installation method. The Standard select decides which part it reads. It reads AS/NZS 3008.1.2:2017 for New Zealand or AS/NZS 3008.1.1 for Australia. For Australia, the Edition select picks 2025 or the superseded 2017 edition.
- Correction factors. It multiplies the ambient, grouping, soil, burial depth and harmonic factors into one correction factor (derating factor in 2017). It divides the design current by that factor. Above 33 % third harmonic, it uses the neutral current instead. The result is the current the cable must carry in the table.
- Voltage drop. It works out the drop for the run length, the power factor and the conductor. It compares the drop with the limit you set. The default limit is 5 %.
- Protective device. If you name a device, its rating must sit at or below the derated capacity. The circuit's earth fault loop impedance must stay under the maximum for that device.
- Fault withstand. If you enter a prospective fault current, the conductor must withstand it for the clearing time. The k factor sets that limit. It depends on the material, the insulation and the conductor size.
- Result. The tool lists each size that fails and the check it failed. Each step names its table or clause where one applies.
| Step | Table or clause | What it decides |
|---|---|---|
| Current rating | Table 13 or 14 for multicore, Tables 4, 5, 7 and 8 for single core | The current each size carries in your installation method |
| Ambient | Tables 27(1) and 27(2) | The correction factor for the air or soil temperature |
| Grouping | Tables 22, 25(1) and 25(2) | The correction factor for circuits run together |
| Buried cable | Table 29, Tables 28(1) and 28(2) | The correction factors for soil resistivity and depth |
| Harmonics | Table 2 and Cl 3.5.9 | The reduction for third harmonic current in the neutral |
| Required current | AS/NZS 3000 Cl 3.4 | The current the cable must carry after correction |
| Voltage drop | Tables 30, 34 and 35, Cl 4.5, AS/NZS 3000 Cl 3.6.2 | The drop over the run and the limit it must meet |
| Device | AS/NZS 3000 Cl 2.5.3.1 | That the rating sits between the design current and the capacity |
| Earth and Zs | AS/NZS 3000 Table 5.1 and Table 8.1 | The earth conductor size and the maximum loop impedance |
| Fault withstand | Table 52 and Cl 5.3 | The k factor and the smallest size that survives the fault |
Tables without a standard named are in the part of AS/NZS 3008.1 you pick. AS/NZS 3008.1.1:2025 numbers them by section, such as Table 3.18 for Table 13.
Common circuits, worked with the tool
Each line states its route. Change one input and the size can change, so run your own circuit before you buy cable. Every line uses multicore copper with PVC insulation and one circuit on the route. The power factor is 0.9, except where a line names a different value. Ze is 0.35 Ω and every size uses the New Zealand tables.
- Lighting, 10 A single‑phase over 40 m. Enclosed in air at 30 °C with a 10 A C curve device. It needs 2.5 mm² with a 2.84 % drop.
- Socket‑outlets, 20 A single‑phase over 30 m. Enclosed in air at 30 °C with a 20 A C curve device. It needs 2.5 mm² with a 4.25 % drop, close to the 5 % limit.
- Cooker, 32 A single‑phase over 15 m. Enclosed in air at 30 °C with a 32 A C curve device. It needs 6 mm² with a 1.43 % drop.
- Shed supply, 32 A single‑phase over 40 m. Enclosed in air at 30 °C with a 32 A C curve device. It needs 6 mm² with a 3.8 % drop.
- EV charger, 32 A single‑phase over 25 m. Partly in insulation at 35 °C, with no wiring enclosure. It has a power factor of 1 and a 32 A C curve device. It needs 10 mm² with a 1.55 % drop.
- Single‑phase mains, 63 A over 20 m. Enclosed in air at 30 °C with a 63 A C curve device. It needs 16 mm² with a 1.42 % drop.
- Three‑phase submain, 100 A at 400 V over 60 m. Enclosed in air at 30 °C. The tool checks no device on this route. It needs 35 mm² with a 1.59 % drop.
New Zealand and Australia
The Standard select picks the part of AS/NZS 3008.1 the tool reads. Part 1.2 holds the New Zealand tables. They assume 30 °C air and 15 °C soil. Part 1.1 holds the Australian tables. They assume 40 °C air and 25 °C soil. The checks from AS/NZS 3000 are the same in both countries.
For Australia, the Edition select picks AS/NZS 3008.1.1:2025 or the superseded 2017 edition. A new calculation starts on 2025. A link with no edition reads 2017, so an old link keeps its numbers.
A single‑phase circuit at 32 A runs 25 m on the 2025 Australian edition. It sits enclosed in air at 40 °C, grouped with one other circuit. It needs 10 mm² with a derated capacity of 35.2 A. Open the Australian example.
A three‑phase circuit at 30 A and 400 V runs 30 m, buried direct in soil at 25 °C. On the 2025 edition it needs 2.5 mm² with a derated capacity of 34 A. The 2017 edition gives 4 mm² with a derated capacity of 33 A. Open it on 2025 or on 2017.
Keep the result
Every input sits in the page address, so the link in your browser reproduces the calculation. The PDF button prints the result with its steps and table references. Saving a calculation to a project needs a free account.
See also: Cable size for a 32 A single‑phase 25 m run, EV charger cable size for a 7 kW 32 A circuit and Current-carrying capacity and derating.
Mga tanong
Design aid ang resulta. I-verify ito laban sa kasalukuyang standard.
Anong laki ng cable ang kailangan ko para sa 32 A circuit sa NZ?
10 mm² copper sa karaniwang ruta. Single‑phase ang circuit, 32 A, sa haba na 25 m. Enclosed sa hangin sa 35 °C, naka-group kasama ang isa pang circuit. Ang derated capacity nito ay 37.6 A at ang voltage drop ay 1.42 %. Iba ang sagot kapag iba ang ruta, kaya ilagay ang sarili mong inputs.
Kaya ba ng 6 mm² cable ang 40 A?
Hindi sa karaniwang ruta. Ang ruta ay may haba na 20 m sa 40 A single‑phase, enclosed in air sa 30 °C. Sa ruta na iyon, bumabagsak ang 6 mm² copper sa current capacity check. Pinipili ng tool ang 10 mm², na may 50 A ng derating capacity. Hindi nito binabago ang resulta kahit mas maikli ang run, dahil ang capacity ay nakadepende sa ruta, hindi sa haba.
Anong laki ng cable para sa 63 A three‑phase submain?
25 mm² copper sa route na ito, na may 95 A derated capacity. May run na 35 m sa 63 A, 400 V, XLPE, nakabalot sa hangin sa 35 °C. Ang device ay 63 A C curve, at ang Ze ay 0.3 Ω. Pumapasa sa current at drop checks ang 16 mm², pero ang loop impedance nitong 0.49 Ω ay bagsak sa Table 8.1.
Gumagana ba ang cable size calculator para sa Australia?
Oo. Itakda ang Standard sa AU · AS/NZS 3008.1.1. Pagkatapos, pipiliin ng Edition select ang AS/NZS 3008.1.1:2025, ang default, o ang napalitang 2017 edition. Piliin ang 2017 para maulit ang mas lumang disenyo. Parehong edition ang gumagamit ng 40 °C na hangin at 25 °C na lupa. Ang NZ · AS/NZS 3008.1.2 ang default na Standard. Ang mga check ng AS/NZS 3000, na madalas isulat bilang AS3000, ay pareho sa dalawang bansa.
Aling AS/NZS 3008 table ang ginagamit ng cable size calculator?
Sa AS/NZS 3008.1.2:2017 o 3008.1.1:2017, ang single‑core ratings ay galing sa Tables 4, 5, 7 at 8, at ang multicore ay sa 13 at 14. Ang derating ay galing sa Tables 22 at 25 hanggang 29, ang impedance ay sa Tables 30 hanggang 35, at ang k ay sa Table 52. Nire-renumber ng AS/NZS 3008.1.1:2025 ang bawat isa, kaya ang Table 13 ay 3.18. Ang AS/NZS 3000:2018 Tables 5.1 at 8.1 ang nagbibigay ng earth size at maximum Zs.
- What size cable for power points in NZ?
- What size cable for power points in Australia?
- What size cable for a lighting circuit in NZ?
- What size cable for a 25 A circuit?
- What size cable for a 22 kW EV charger?
- How many amps can 1.5 mm² cable carry?
- How many amps can 2.5 mm² cable carry?
- How many amps can 2.5 mm² carry in Australia?
- How many amps can 6 mm² cable carry?
- How many amps can 10 mm² cable carry?
- How many amps can 16 mm² cable carry?
- Minimum cable size for a lighting circuit
- Minimum cable size for power points
- How many power points on a 20 A circuit?
- How many lights on a 10 A circuit?
- Voltage drop on 2.5 mm² over 30 m
Mga worked example
- Car-park floodlight: obtrusive light at a boundaryTwo 10 000 lm floodlights 10 m from a neighbour's window in zone A2, checked against AS/NZS 4282 for lux at the window, candela and the upward light ratio.
- Cable tray fill for a plant room: a second tierLay ten multicore cables on a 300 mm perforated tray in one layer, see when it takes a second tier, and carry the grouping factor into the cable size.
- Hot water cylinder cable size for a 3 kW elementA 16 A hot water circuit run 20 metres through wall insulation at 35 degrees, sized to 2.5 mm² with 17.86 A of derated capacity and 2.27 % voltage drop.
- Motor circuit for a 15 kW pump: DOL or star-deltaSize a 15 kW 400 V pump circuit: cable, breaker, contactor and overload relay. Compare DOL, star-delta, soft starter and drive starts.
- Submain cable size for 3‑phase 100 A over 60 mA 100 A tenancy submain on tray over 60 m at 40 °C. See the derating chain, the four checks and why the loop impedance check sets the size at 70 mm².
- Factory power factor correction: 250 kW at 0.78A 250 kW factory load at 0.78 power factor lifted to 0.95. The kvar, the capacitor steps, the current saved, the kVA released and why the bank is detuned.
Background
- Conduit fill and installation methodsHow the conduit space factor works, what the fill percent means against the 40 % limit, and how the install method names on site map to the 3008 columns.
- Current-carrying capacity and deratingWhy one cable size has many ratings. Install method, ambient, grouping, soil and depth, with a 25 A circuit that needs 10 mm² once the factors apply.
- MEN system: multiple earthed neutral explainedMEN means multiple earthed neutral. In NZ, earth and neutral join at the main switchboard. A fault on a 32 A C curve circuit then draws 343.8 A and clears.
- The 5 % voltage drop limit from supply to loadWhat AS/NZS 3000 Cl 3.6.2 limits, how the drop of the mains, submains and final subcircuits adds by percent, the four exceptions and why any split is yours.
- Voltage drop basicsOhm's law on a cable, the mV/A·m shortcut, the percent limit and the maximum length, worked on a 25 A run over 35 m of 4 mm² copper.
- AS/NZS 3008.1.1:2025: what the AU part coversWhat AS/NZS 3008.1.1:2025 covers, a.c. to 0.6/1 kV and d.c. to 1500 V at 40 °C air and 25 °C soil, how its sections run, and where the d.c. tables are.
Mga clause at table na binabasa ng tool na ito
- AS/NZS 3000:2018 Cl 2.5.3.1Protective device coordination
- AS/NZS 3000:2018 Cl 3.4Current-carrying capacity
- AS/NZS 3000:2018 Cl 3.6.2Voltage drop limit
- AS/NZS 3000:2018 Cl 5.7.4Earth fault loop impedance
- AS/NZS 3008.1.2:2017 Cl 3.5.2.6(a)Groups of circuits in underground wiring enclosures
- AS/NZS 3008.1.2:2017 Cl 3.5.9Third harmonic current in the neutral
- AS/NZS 3008.1.2:2017 Cl 5.3Short-circuit performance
- AS/NZS 3000:2018 Table 5.1Minimum earthing conductor size by active conductor size
Bawat clause at table, kasama kung paano ito na-verify
Huling na-check ang mga table noong 27 Sept 2026.
Mga kaugnay na tool
- Voltage drop calculatorCalculate voltage drop on a cable run and check the limit.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/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
- Maximum demand calculatorEstimate maximum demand for domestic or non‑domestic loads.AS/NZS 3000 Table C1/C2
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