What is the ampacity of 12 AWG wire?

20 A at 60 °C insulation, 25 A at 75 °C and 30 A at 90 °C, for copper with not more than three current-carrying conductors in a raceway at 30 °C ambient. A 20 A circuit on 12 AWG is the common residential case, using the 60 °C column because the terminations are rated 60 °C.

What is the ampacity of 10 AWG wire?

30 A at 60 °C, 35 A at 75 °C and 40 A at 90 °C for copper, under the same conditions as the table. A 30 A circuit is the common residential use for 10 AWG — dryers, ranges and some air conditioners.

Does 60 °C or 75 °C apply to my circuit?

Use the lowest temperature rating of any component in the circuit — conductor, termination, breaker or device. Because most common breakers and receptacles are rated 60 °C or 75 °C, the 90 °C column is normally used only as the starting point for derating calculations, not as the circuit ampacity.

Is ampacity the same for aluminium wire?

No. Aluminium conductors carry less current than copper at the same size and require their own column. Aluminium is also more prone to termination problems, so it is usually installed one or two sizes larger than the copper equivalent.

What is the ampacity of 4/0 copper?

195 A at 60 °C, 230 A at 75 °C and 260 A at 90 °C. This is a common service-entrance size for a 200 A residential service.

Why does the table stop at 1000 kcmil?

Above 1000 kcmil parallel conductors become the practical choice, so the table continues in kcmil sizes up to that point and larger services are built from sets of smaller conductors run in parallel.

Wire Ampacity Chart

Allowable current-carrying capacity for copper conductors by wire size and insulation temperature rating, per NEC Table 310.16.

Page last changed 2026-10-19 · based on NEC 2023 (NFPA 70-2023)

Quick Answer

Ampacity depends on the insulation temperature rating, not just the wire size — the same conductor carries more current at a higher rating. A 12 AWG copper conductor carries 20 A at 60 °C, 25 A at 75 °C and 30 A at 90 °C. Choose the rating that matches the weakest component in the circuit, including terminations.

Find a wire size

Copper Conductor Ampacity (NEC 310.16)

Size^[1]	60 °C A^[1]	75 °C A^[1]	90 °C A^[1]
14 #	15	20	25
12 #	20	25	30
10 #	30	35	40
8 #	40	50	55
6 #	55	65	75
4 #	70	85	95
3 #	85	100	115
2 #	95	115	130
1 #	110	130	145
1/0 #	125	150	170
2/0 #	145	175	195
3/0 #	165	200	225
4/0 #	195	230	260
250 kcmil #	215	255	290
300 kcmil #	240	285	320
350 kcmil #	260	310	350
400 kcmil #	280	335	380
500 kcmil #	320	380	430
600 kcmil #	350	420	475
700 kcmil #	385	460	520
750 kcmil #	400	475	535
1000 kcmil #	455	545	615

Values are for copper conductors, not more than three current-carrying conductors in a raceway or cable, in an ambient temperature of 30 °C. Correction factors apply for higher ambient temperature and for more conductors. Terminations are typically rated lower than the conductor — the lower of the two governs.

Why Three Columns

Ampacity is limited by how hot the insulation is allowed to get. The same copper conductor carries more current with 90 °C insulation than with 60 °C insulation, because more heat can be tolerated before the insulation degrades.

But the conductor is rarely the weakest link. Common circuit breakers, receptacles and other terminations are usually rated 60 °C or 75 °C, and the code requires the lowest rating in the circuit to be used for the ampacity calculation. A 90 °C conductor on a 75 °C breaker is a 75 °C circuit.

The 90 °C column is used mainly for derating calculations, where the higher starting value leaves more margin after correction factors are applied — not as the circuit's actual ampacity.

What Changes the Number

Ampacity from the table is a starting point. Several adjustments apply:

Ambient temperature — above 30 °C the conductor runs hotter, so capacity is reduced by an ambient correction factor.
Number of conductors — more than three current-carrying conductors bundled together means less heat can escape, so an adjustment factor applies.
Continuous loads — a load expected to run three hours or more must be sized at 125% of its rating.
Voltage drop — on long runs the allowable drop of a few percent often forces a larger conductor before ampacity becomes the limit.

Frequently Asked Questions

What is the ampacity of 12 AWG wire?: 20 A at 60 °C insulation, 25 A at 75 °C and 30 A at 90 °C, for copper with not more than three current-carrying conductors in a raceway at 30 °C ambient. A 20 A circuit on 12 AWG is the common residential case, using the 60 °C column because the terminations are rated 60 °C.
What is the ampacity of 10 AWG wire?: 30 A at 60 °C, 35 A at 75 °C and 40 A at 90 °C for copper, under the same conditions as the table. A 30 A circuit is the common residential use for 10 AWG — dryers, ranges and some air conditioners.
Does 60 °C or 75 °C apply to my circuit?: Use the lowest temperature rating of any component in the circuit — conductor, termination, breaker or device. Because most common breakers and receptacles are rated 60 °C or 75 °C, the 90 °C column is normally used only as the starting point for derating calculations, not as the circuit ampacity.
Is ampacity the same for aluminium wire?: No. Aluminium conductors carry less current than copper at the same size and require their own column. Aluminium is also more prone to termination problems, so it is usually installed one or two sizes larger than the copper equivalent.
What is the ampacity of 4/0 copper?: 195 A at 60 °C, 230 A at 75 °C and 260 A at 90 °C. This is a common service-entrance size for a 200 A residential service.
Why does the table stop at 1000 kcmil?: Above 1000 kcmil parallel conductors become the practical choice, so the table continues in kcmil sizes up to that point and larger services are built from sets of smaller conductors run in parallel.

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#	Source	Type	Revision / method
[1]	NFPA 70 National Electrical Code, Table 310.16 — Ampacities of Insulated Conductors	reference	NEC 2023 (NFPA 70-2023) — source

Data Sources

Standard	Revision	What it covers on this page
NFPA 70 National Electrical Code, Table 310.16	NEC 2023 (NFPA 70-2023)	all ampacity values on this page, for copper conductors at 30 °C ambient

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

These are base ampacities for the stated conditions. Ambient temperature, conductor count, continuous loading and voltage drop all modify the allowable current, and the governing requirement is the adopted code in the jurisdiction of installation.

Accuracy and use. Use the source notes and recorded verification scope above to assess each value. Calculated values follow the stated derivations; compilation values may lack a confirmed original document or product condition. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Read the source notes, calculation methods and verification scope above before reusing a value. To cite this page:

Plain text

Engineering Reference. "Wire Ampacity Chart." https://refmanual.com/charts/ampacity-chart/ (accessed 2026-10-19). Data from NFPA 70 National Electrical Code, Table 310.16, NEC 2023 (NFPA 70-2023).

BibTeX

@misc{ampacity-chart,
  title        = {Wire Ampacity Chart},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/ampacity-chart/}},
  note         = {Accessed: 2026-10-19},
  source       = {NFPA 70 National Electrical Code, Table 310.16, NEC 2023 (NFPA 70-2023)}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Wire Ampacity Chart
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/ampacity-chart/
PY  - 2026
DA  - 2026-10-19
N1  - Source: NFPA 70 National Electrical Code, Table 310.16, NEC 2023 (NFPA 70-2023)
ER  -

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