📊Wire gauge chart

By the AmpSizer editorial desk

✓ Tested & verified Updated: Aug 10, 2026 How we calculate this

A wire gauge chart pairs every conductor size with three things: its cross-sectional area, its resistance, and how many amps it is allowed to carry. In American Wire Gauge the numbers run backwards — 14 AWG is thinner than 6 AWG — and above 4/0 the scale switches to thousands of circular mils.

The figures below are NEC Table 310.16 for ampacity and Chapter 9, Table 8 for area and resistance, generated from the same data files the calculators on this site read.

Five numbers worth remembering, all of them from the tables on this page:

12 AWG copper carries 25 A at 75 °C and is still a 20 amp circuit, because 240.4(D) caps it.
Every three gauge numbers doubles the area: 14 AWG is 2.08 mm², 11 would be 4.17, 8 AWG is 8.37.
Aluminium needs two sizes more than copper for the same current — 4/0 aluminium and 2/0 copper are both about 180 A at 75 °C.
12 AWG copper has 1.98 ohms per 1,000 ft, which is why 100 ft at 20 A costs 7.9 volts.
One kcmil is 0.5067 mm², so 12 AWG is 3.31 mm² — between the stocked metric sizes of 2.5 and 4.
Mechanical horsepower is 745.7 W and metric horsepower (PS, CV) is 735.5 W, a 1.4% gap that lands on a code-table boundary often enough to matter.

The complete chart

Size, area, ampacity in all three temperature columns for both metals, and resistance. This is the table the rest of this site is built on.

Conductor size, area, resistance and allowable ampacity. Ampacity is NEC Table 310.16 — not more than three current-carrying conductors in a raceway, cable or earth, at 86 °F (30 °C) ambient. Correct it for heat and for bundling before you use it.
Size	kcmil	mm²	Cu 60 °C	Cu 75 °C	Cu 90 °C	Al 75 °C	Cu Ω/kft	Al Ω/kft
14 AWG	4.11	2.08	15 A	20 A	25 A	—	3.14	—
12 AWG	6.53	3.31	20 A	25 A	30 A	20 A	1.98	3.18
10 AWG	10.38	5.261	30 A	35 A	40 A	30 A	1.24	2
8 AWG	16.51	8.367	40 A	50 A	55 A	40 A	0.778	1.26
6 AWG	26.24	13.3	55 A	65 A	75 A	50 A	0.491	0.808
4 AWG	41.74	21.15	70 A	85 A	95 A	65 A	0.308	0.508
3 AWG	52.62	26.67	85 A	100 A	115 A	75 A	0.245	0.403
2 AWG	66.36	33.62	95 A	115 A	130 A	90 A	0.194	0.319
1 AWG	83.69	42.41	110 A	130 A	145 A	100 A	0.154	0.253
1/0 AWG	105.6	53.49	125 A	150 A	170 A	120 A	0.122	0.201
2/0 AWG	133.1	67.43	145 A	175 A	195 A	135 A	0.0967	0.159
3/0 AWG	167.8	85.01	165 A	200 A	225 A	155 A	0.0766	0.126
4/0 AWG	211.6	107.2	195 A	230 A	260 A	180 A	0.0608	0.1
250 kcmil	250	127	215 A	255 A	290 A	205 A	0.0515	0.0847
300 kcmil	300	152	240 A	285 A	320 A	230 A	0.0429	0.0707
350 kcmil	350	177	260 A	310 A	350 A	250 A	0.0367	0.0605
400 kcmil	400	203	280 A	335 A	380 A	270 A	0.0321	0.0529
500 kcmil	500	253	320 A	380 A	430 A	310 A	0.0258	0.0424
600 kcmil	600	304	350 A	420 A	475 A	340 A	0.0214	0.0353
700 kcmil	700	355	385 A	460 A	520 A	375 A	0.0184	0.0303
750 kcmil	750	380	400 A	475 A	535 A	385 A	0.0171	0.0282

Size, area and the metric equivalent

The same conductors by area and diameter, with the space each one occupies as insulated THHN — which is what conduit fill is calculated from. The mm² column is the bridge for anyone working from a metric drawing or buying cable by cross-section; one kcmil is 0.5067 mm².

Conductor size, area, resistance and allowable ampacity. Ampacity is NEC Table 310.16 — not more than three current-carrying conductors in a raceway, cable or earth, at 86 °F (30 °C) ambient. Correct it for heat and for bundling before you use it.
Size	kcmil	mm²	Diameter, in	THHN area, in²
14 AWG	4.11	2.08	0.073	0.0097
12 AWG	6.53	3.31	0.092	0.0133
10 AWG	10.38	5.261	0.116	0.0211
8 AWG	16.51	8.367	0.146	0.0366
6 AWG	26.24	13.3	0.184	0.0507
4 AWG	41.74	21.15	0.232	0.0824
3 AWG	52.62	26.67	0.26	0.0973
2 AWG	66.36	33.62	0.292	0.1158
1 AWG	83.69	42.41	0.332	0.1562
1/0 AWG	105.6	53.49	0.373	0.1855
2/0 AWG	133.1	67.43	0.419	0.2223
3/0 AWG	167.8	85.01	0.47	0.2679
4/0 AWG	211.6	107.2	0.528	0.3237
250 kcmil	250	127	0.575	0.397
300 kcmil	300	152	0.63	0.4608
350 kcmil	350	177	0.681	0.5242
400 kcmil	400	203	0.728	0.5863
500 kcmil	500	253	0.813	0.7073
600 kcmil	600	304	0.893	0.8676
700 kcmil	700	355	0.964	0.9887
750 kcmil	750	380	0.998	1.0496

The two scales interleave rather than align, so a conversion is a reading and not a substitution: 12 AWG is 3.31 mm², which is between the stocked 2.5 and 4 mm² sizes. Round up, and see AWG to mm² for the full pairing table and the other unit conversions this site uses. Calculations follow the US NEC; outside the US, follow your local electrical code.

Breaker pairings

The device each size supports at 75 °C on a short run, with the ground that goes with it. The gap between the ampacity column above and the breaker column here is 240.4(D) doing its work.

Breaker rating against the smallest conductor that carries it at 75 °C, with no derating and a short run. Computed from NEC Table 310.16, 240.4(D) and Table 250.122.
Breaker	Copper	Aluminium	Copper ground	What it usually feeds
15 A	14 AWG	12 AWG	14 AWG	Lighting and general receptacles
20 A	12 AWG	12 AWG	12 AWG	Kitchen, bathroom and garage receptacles
30 A	10 AWG	10 AWG	10 AWG	Dryer, small water heater, RV outlet
40 A	8 AWG	8 AWG	10 AWG	Range, 40 A EV charger
50 A	8 AWG	6 AWG	10 AWG	Range, welder, 50 A EV charger, hot tub
60 A	6 AWG	4 AWG	10 AWG	Sub panel, large hot tub, tankless heater
70 A	4 AWG	3 AWG	8 AWG	Sub panel, larger tankless heater
100 A	3 AWG	1 AWG	8 AWG	Sub panel, or a small service
125 A	1 AWG	2/0 AWG	6 AWG	Sub panel
150 A	1/0 AWG	3/0 AWG	6 AWG	Service, or a large sub panel
200 A	3/0 AWG	250 kcmil	6 AWG	Typical whole-house service

How to read the gauge scale

Three properties of AWG make it possible to work in your head, and all three come from the fact that the scale is geometric rather than linear.

Three gauges doubles the area. 14 to 11 doubles it, 12 to 9 doubles it, 10 to 7 doubles it. Since 11, 9 and 7 are not stocked, the practical version is that two stocked sizes up is roughly double — 14 to 10, 12 to 8, 10 to 6.

Six gauges doubles the diameter and quadruples the area.

Ten gauges is a factor of ten in area. 20 AWG to 10 AWG is ten times the copper, which is a handy sanity check when a number looks wrong.

Above 4/0 the scale is abandoned and sizes are quoted in kcmil, where the number is the area in thousands of circular mils. 250 kcmil is 250,000 circular mils, which is 127 mm², which is about 18% more than 4/0.

What the chart cannot tell you

Ampacity in a table is a starting figure under standard conditions, and three things move it on a real installation.

Ambient temperature. Above 86 °F the correction factors of Table 310.15(B)(1) apply, and at 122 °F a 75 °C conductor is down to 75% of its listed value.

How many conductors are together. More than three current-carrying conductors in one raceway brings in Table 310.15(C)(1): 80% at four to six, 70% at seven to nine, 50% at ten to twenty.

Distance. The chart has no distance in it at all, and on a long run voltage drop rather than ampacity is what decides the size. That is a separate calculation, and it is the one the voltage drop calculator does.

For the corrections applied automatically, use the wire ampacity calculator; for the whole circuit at once, the wire size calculator.

Frequently asked questions

What is the difference between AWG and kcmil?

AWG is a gauge number that gets smaller as the wire gets thicker, and it runs out at 4/0. Above that, sizes are given directly in thousands of circular mils — 250 kcmil, 500 kcmil — which is an area rather than a gauge. The changeover is why 4/0 and 250 kcmil sit next to each other in every table despite looking like different kinds of number.

Why do AWG numbers get smaller as the wire gets bigger?

Because the gauge counts drawing operations. Wire was made by pulling it through progressively smaller dies, and the number recorded how many passes it took — more passes, thinner wire, higher number. The mathematics fell out of that: each three gauge numbers is almost exactly a doubling of area, and each six is a doubling of diameter.

How many amps can each wire size carry?

At a 75 °C terminal, copper: 14 AWG 20 A, 12 AWG 25 A, 10 AWG 35 A, 8 AWG 50 A, 6 AWG 65 A, 4 AWG 85 A, 2 AWG 115 A, 1/0 150 A, 4/0 230 A. The 14, 12 and 10 gauge circuits are then limited to 15, 20 and 30 amp devices by 240.4(D), which is the rule that makes the chart and the real world differ.

Is a wire gauge chart the same in Canada or Europe?

Canada uses AWG and the Canadian Electrical Code, with ampacity tables that resemble the NEC but are not identical. Europe uses cross-section in square millimetres and the IEC tables, which are organised by installation method rather than by temperature column. The mm² column here is the bridge, but the ampacity figures are US and do not transfer.

Which temperature column should I use?

The one matching the lowest-rated part of the circuit, which is almost always the terminals — and almost always 75 °C. 110.14(C) requires it. The 90 °C column exists so that you can apply derating factors from a higher starting point before being limited back down, not so you can use a smaller conductor.

How we calculate this

Every table on this page is generated at build time from the data files this site’s calculators read, so a figure here and an answer from a widget cannot drift apart. Ampacity is NEC Table 310.16: not more than three current-carrying conductors in a raceway, cable or directly buried, at an ambient of 30 °C (86 °F). Area in circular mils and square millimetres, conductor diameter and direct-current resistance are NEC Chapter 9, Table 8, for stranded uncoated conductors. Insulated conductor areas are Chapter 9, Table 5. The breaker column is the largest standard rating in 240.6(A) that the conductor supports, with the small-conductor ceiling of 240.4(D) applied to 14, 12 and 10 AWG.

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