Tātaitai rahi taura
Tātaitai rahi taura kore utu mō Aotearoa me Ahitereiria. Ka pānui i AS/NZS 3008.1.2:2017, i AS/NZS 3008.1.1:2025 rānei me te 2017 ka kōwhiria, ā, ka arotake i 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.
Whakamātau mahi 24
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- 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.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Ngā wāhanga
- Wāhanga toru
- Voltage
- 400 V
- Iahiko hoahoa
- 50 A
- Power factor
- 0.9
- Paerewa
- NZ · AS/NZS 3008.1.2
- Roa rerenga
- 60 m
- Tikanga whakaurunga
- Kua kōpakina ki te hau
- Pāmahana taiao
- 30 °C
- Ngā ara iahiko whakarōpū
- 1
- Ihinga harmonic tuatoru
- 0 %
- Rauemi
- Parahi
- Insulation
- PVC 75 °C
- Ngā matua
- Multicore
- Ngā waea i te whakarite
- 1
- Rohe heke voltage
- 5 %
- Tirohia te taputapu tiaki
- Kāo
- Iahiko hapa ka puta pea
- 0 kA
Rahi kaikawe
10mm²
- Kaha kua whakaiti
- 50A
- Heke voltage
- 2.66%
- Kaikawe whenua
- 4mm²
- Tauwehe whakaheke katoa
- 1.00
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Tauutu whakaheke pāmahana taiao×1.00
AS/NZS 3008.1.2:2017 Tables 27(1), 27(2) p.88
- Tauwehe whakaheke whakarōpū×1.00
One circuit, no grouping factor
- Tauwehe whakaiti oneone×1.00
AS/NZS 3008.1.2:2017 Table 29 p.90
- Tauutu whakaheke hōhonu tanu×1.00
AS/NZS 3008.1.2:2017 Tables 28(1), 28(2) p.89
- Tauwhāinga whakaiti katoa×1.00
- Au ripanga e hiahiatia ana50A
AS/NZS 3000:2018 Cl 3.4
- Rahi kaikawe kua kōwhiriaHua10mm²
AS/NZS 3008.1.2:2017 Table 13 p.62–64
- Kaha au whakaheke50A
AS/NZS 3000:2018 Cl 3.4
- Heke whakahiato2.66%
Mō tēnei tātaitai
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.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He rahi taura pēhea me whai au mō tētahi ara iahiko 32 A i NZ?
10 mm² parahi i runga i tētahi ara tauira. He ara iahiko wāhanga kotahi, 32 A, 25 m te roa. Kua kōpakina, i te hau 35 °C, ā, kua whakarōpūtia me tētahi atu ara iahiko kotahi. Ko tōna kaha kua whakaitihia (derated) he 37.6 A, ā, ko te heke voltage he 1.42 %. He rerekē te otinga mō tētahi ara rerekē, nō reira whakaurua ō ake uara.
Ka taea e tētahi taura 6 mm² te kawe i te 40 A?
Ehara i te ara tauira. Ka roa te ara 20 m mō te 40 A wāhanga kotahi, kua kōpakina ki te hau i te 30 °C. I runga i taua ara, ka hinga te parahi 6 mm² i te arotake kaha kawe iahiko. Ka kōwhiri te taputapu i te 10 mm², me te 50 A o te kaha derating. Kāore e panoni tērā e te ara poto ake, nā te mea ko te ara te mea e whakatau ana i te kaha, ehara i te roa.
He rahi taura pēhea mō tētahi submain wāhanga toru 63 A?
25 mm² parahi i tēnei ara, me te kaha derating 95 A. E 35 m te roa, 63 A, 400 V, XLPE, kua kāpehia ki te hau i 35 °C. Ko te taputapu he C curve 63 A, ā, he 0.3 Ω te Ze. E whakatutuki ana te 16 mm² i ngā arotake iahiko me te heke, engari kāore ia e whakatutuki i Table 8.1 i tōna loop impedance 0.49 Ω.
Ka mahi te tātaitai rahi taura mō Ahitereiria?
Āe. Whakatakotoria te Standard ki AU · AS/NZS 3008.1.1. Ka kōwhiri te Edition i AS/NZS 3008.1.1:2025, ko te taunoa, i te putanga 2017 kua whakakahoretia rānei. Kōwhiria te 2017 hei whakahou i tētahi hoahoa tawhito. Ka whakamahia e ngā putanga e rua te hau 40 °C me te oneone 25 °C. Ko NZ · AS/NZS 3008.1.2 te Standard taunoa. Ko ngā tātari AS/NZS 3000, he mea tuhi ai ko AS3000 te ingoa, he ōrite i ngā whenua e rua.
Ko ēhea ngā ripanga AS/NZS 3008 e whakamahia ana e te tātaitai Rahi Taura?
I raro i AS/NZS 3008.1.2:2017 me 3008.1.1:2017, ka ahu mai ngā reiti single‑core i ngā Tables 4, 5, 7 me 8, ā, ko ngā multicore i 13 me 14. Ko te derating i ngā Tables 22 me 25 ki 29, ko te impedance i ngā Tables 30 ki 35, ko te k i Table 52. Ka whakahou anō a AS/NZS 3008.1.1:2025 i ia tau, nā reira ko Table 13 ko 3.18. Ka hoatu a AS/NZS 3000:2018 Tables 5.1 me 8.1 i te rahi whenua me te Zs nui rawa.
- 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
Ngā tauira mahi
- 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.
Kōrero o muri
- 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.
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
- 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
Ia Clause me Table, me te pēhea i manatokotia ai ia tētahi
Ngā tūtohi i arotakehia whakamutunga i te 27 Sept 2026.
Ngā taputapu hononga
- Tātaitai heke voltageCalculate voltage drop on a cable run and check the limit.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai correction factorRead each correction factor and the rating a cable needs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai Maximum DemandEstimate maximum demand for domestic or non‑domestic loads.AS/NZS 3000 Table C1/C2
He whai hua tēnei?
He pātai, he uara rānei e kitea ana he hē? Whakapā mai.