Wire gauge chart & 1:1 screen sizer

Wire gauge chart from 40 AWG to 500 kcmil with diameter, mm², amps and a true-size screen caliper. 12 AWG is 2.05 mm of copper, good for 20 A. Or skip the math: a 48 A EV charger takes 6 AWG copper THHN on a 60 A breaker in 3/4" EMT, or 4 AWG NM-B in the wall.

Drawing at true size…

Quick Project Finder · 48 A EV

EV charger, 48 A hardwired · 50 ft one way, THHN copper in EMT

USE:

6 AWG COPPER WIRE · 60 A 2-POLE BREAKER · 3/4" EMT CONDUIT

Wire

6 AWG

copper THHN

Breaker

60 A

2-pole

Conduit

3/4" EMT

ground 10 AWG

Safe for up to 65 A (75 °C THHN terminals) on a 60 A breaker, and carries a continuous 48 A load up to 152 feet one way with under 3% voltage drop.

Meets NEC 2023 Table 310.16 at 75°C — verify with your local AHJ/inspector110.14(C)
Continuous load × 125 % = 60 A ≤ 65 A625.40
0.98 % drop at 50 ft210.19 IN

The answer

Wire: 2 × 6 AWG THHN copper + 10 AWG groundTHHN copper in EMT
Breaker: 60 A 2-pole2-pole, 240 V
Ground: 10 AWG copperTable 250.122 for 60 A
Conduit: 3/4" EMT23.0 % full of 40 %
Max distance at this size: 152 ft one wayunder 3 % drop at 48 A

How it was worked out

Allowable ampacity: 65 A6 AWG, 75 °C column
Load used for the drop: 48 A continuousEV charging is a continuous load
Smallest size before distance: 6 AWG
With In-wall NM-B cable: 4 AWGNM-B is limited to the 60 °C column

6 AWG

Copper 60 / 75 / 90 °C: 55 / 65 / 75 ANM-B uses the 60 °C column (334.80)
Aluminum 60 / 75 / 90 °C: 40 / 50 / 55 A
Largest breaker (Cu, 75 °C): 60 Aampacity ≥ breaker
Solid diameter: 0.162"4.12 mm · ASTM B258 formula
Stranded (7 strands): 0.184"4.67 mm · Table 8
THHN outside: 0.254"6.45 mm · 0.0507 in² · Table 5
Area: 26,240 cmil13.30 mm² · nearest IEC 16 mm²

Wire gauge reference 67 rows

Sort any column, print a shop sheet, download CSV. Click a row to load it in the calculator.

AWG wire gauge chart: diameter, area, resistance and ampacity

31 rows

Download CSV

American Wire Gauge sizes from 500 kcmil to 40 AWG: solid diameter in inches and millimetres, Table 8 stranding and stranded diameter, cross-section in circular mils and mm², DC resistance at 75 °C and NEC Table 310.16 copper ampacity

0.7071"	17.96	37 × · 0.813"	500,000	253.35	0.0258	320	380	430
0.6325"	16.06	37 × · 0.728"	400,000	202.68	0.0321	280	335	380
0.5916"	15.03	37 × · 0.681"	350,000	177.35	0.0367	260	310	350
0.5477"	13.91	37 × · 0.630"	300,000	152.01	0.0429	240	285	320
0.5000"	12.70	37 × · 0.575"	250,000	126.68	0.0515	215	255	290
0.4600"	11.68	19 × · 0.528"	211,600	107.22	0.0608	195	230	260
0.4096"	10.40	19 × · 0.470"	167,800	85.03	0.0766	165	200	225
0.3648"	9.27	19 × · 0.418"	133,100	67.44	0.0967	145	175	195
0.3249"	8.25	19 × · 0.372"	105,600	53.51	0.122	125	150	170
0.2893"	7.35	19 × · 0.332"	83,690	42.41	0.154	110	130	145
0.2576"	6.54	7 × · 0.292"	66,360	33.63	0.194	95	115	130
0.2294"	5.83	7 × · 0.260"	52,620	26.66	0.245	85	100	115
0.2043"	5.19	7 × · 0.232"	41,740	21.15	0.308	70	85	95
0.1620"	4.12	7 × · 0.184"	26,240	13.30	0.491	55	65	75
0.1285"	3.26	7 × · 0.146"	16,510	8.37	0.778	40	50	55
0.1019"	2.59	7 × · 0.116"	10,380	5.26	1.24	30	35	40
0.0808"	2.053	7 × · 0.0920"	6,530	3.31	1.98	20	25	30
0.0641"	1.628	7 × · 0.0730"	4,110	2.08	3.14	15	20	25
0.0508"	1.291	7 × · 0.0580"	2,580	1.31	4.99	—	—	18
0.0403"	1.024	7 × · 0.0460"	1,620	0.8209	7.95	—	—	14
0.0320"	0.812	—	1,022	0.5179	12.341	—	—	—
0.0253"	0.644	—	642	0.3253	19.646	—	—	—
0.0201"	0.511	—	404	0.2047	31.22	—	—	—
0.0159"	0.405	—	254	0.1287	49.656	—	—	—
0.0126"	0.321	—	160	0.0811	78.829	—	—	—
0.0100"	0.255	—	101	0.0512	124.878	—	—	—
0.0080"	0.202	—	63	0.0319	200.201	—	—	—
0.0063"	0.160	—	40	0.0203	315.317	—	—	—
0.0050"	0.127	—	25	0.0127	504.508	—	—	—
0.0040"	0.101	—	16	0.0081	788.293	—	—	—
0.0031"	0.080	—	10	0.0051	1261.269	—	—	—

Solid diameters from the AWG formula (ASTM B258); stranding, stranded diameters and resistance from NEC Chapter 9 Table 8; ampacity from Table 310.16 (NEC 2023), 30 °C ambient, not more than three current-carrying conductors.

NEC Table 310.16 ampacity, copper

18 rows

Download CSV

NEC 2023 Table 310.16 allowable ampacity of insulated copper conductors at 60, 75 and 90 °C, with the largest standard breaker each may take (240.4(D) small-conductor caps, ampacity at least the breaker rating)

15	20	25	15	14 AWG
20	25	30	20	12 AWG
30	35	40	30	10 AWG
40	50	55	50	10 AWG
55	65	75	60	10 AWG
70	85	95	80	8 AWG
85	100	115	100	8 AWG
95	115	130	110	6 AWG
110	130	145	125	6 AWG
125	150	170	150	6 AWG
145	175	195	175	6 AWG
165	200	225	200	6 AWG
195	230	260	225	4 AWG
215	255	290	250	4 AWG
240	285	320	250	4 AWG
260	310	350	300	4 AWG
280	335	380	300	4 AWG
320	380	430	350	3 AWG

Values agree across Elliott Electric (2020 NEC), Cerrowire (2017 NEC) and Southwire SPEC 10028 (2023 NEC). NEC 2026 adds 16 AWG copper and 14 AWG copper-clad aluminum rows.

Metric wire sizes (mm²) to AWG

18 rows

Download CSV

IEC 60228 metric conductor sizes from 0.5 to 240 mm² with their solid-equivalent diameter, the nearest AWG size and the next AWG size up, and the maximum class 2 and class 5 copper resistance at 20 °C

0.80	20 AWG	20 AWG	36	39
0.98	18 AWG	18 AWG	24.5	26
1.13	18 AWG	16 AWG	18.1	19.5
1.38	16 AWG	14 AWG	12.1	13.3
1.78	14 AWG	12 AWG	7.41	7.98
2.26	12 AWG	10 AWG	4.61	4.95
2.76	10 AWG	8 AWG	3.08	3.3
3.57	8 AWG	6 AWG	1.83	1.91
4.51	6 AWG	4 AWG	1.15	1.21
5.64	3 AWG	3 AWG	0.727	0.78
6.68	2 AWG	1 AWG	0.524	0.554
7.98	1/0 AWG	1/0 AWG	0.387	0.386
9.44	2/0 AWG	3/0 AWG	0.268	0.272
11.00	3/0 AWG	4/0 AWG	0.193	0.206
12.36	250 kcmil	250 kcmil	0.153	0.161
13.82	300 kcmil	300 kcmil	0.124	0.129
15.35	350 kcmil	400 kcmil	0.0991	0.106
17.48	500 kcmil	500 kcmil	0.0754	0.0801

Class 2 is stranded building wire, class 5 is flexible cord. Never substitute a smaller metric size for an AWG size in a US installation.

05 / Field guide

Copper first,
then the code.

A wire gauge is a size of metal, not of plastic. American Wire Gauge numbers run backwards and shrink by a fixed ratio: every 6 gauges the diameter halves, every 3 gauges the area halves. 10 AWG is 2.59 mm of copper, 12 AWG 2.05 mm, 14 AWG 1.63 mm. The chart, the 1:1 caliper and the quick finder above all read from the same tables: NEC 2023 Table 310.16 for amps, Chapter 9 for diameters and resistance.

The AWG formula

AWG (Brown & Sharpe) defines 36 AWG as 0.005 inch and 4/0 as 0.4600 inch, with 39 equal ratio steps between them. That makes the formula below exact for solid wire, and it is why 4/0, 3/0, 2/0 and 1/0 continue the scale past 1 AWG before kcmil (thousands of circular mils) take over at 250.

Stranded wire of the same gauge has the same copper area but a larger outside diameter: 7 strands up to 2 AWG, 19 strands from 1 AWG to 4/0 and 37 strands from 250 to 500 kcmil (NEC Chapter 9 Table 8).

d (in) = 0.005 × 92^((36 − n) / 39) 4/0 = n −3 · 1/0 = n 0 area (cmil) = (1000 × d)²

Three answers for the same wire

Table 310.16 gives every size three ampacities, at 60, 75 and 90 °C. 6 AWG copper is 55 A as NM-B cable (334.80 holds NM-B to 60 °C), 65 A as THHN on 60/75 °C breakers and lugs, and 75 A at 90 °C, a number you may derate from but never use at a terminal.

That is the trap behind the most common homeowner question: a 48 A EV charger is a continuous load and needs 60 A of ampacity, so 6 AWG THHN in conduit works and 6 AWG NM-B (55 A) does not; in the wall it takes 4 AWG NM-B.

Why the screen can be trusted

A browser does not know how big its pixels are, so the gauge starts from a table of 114 phones, tablets, laptops and monitors matched to your screen’s size and pixel ratio, an estimate good to about five percent. Laying a coin or a bank card on the glass and matching its outline replaces the estimate with a measurement good to a fraction of a percent, saved for this screen only.

Browser zoom is corrected automatically from the pixel ratio; pinch zoom is flagged, because nothing drawn is true size until it is undone.

pixels per mm = CSS px across the card ÷ 85.60 mm ID-1 card: 85.60 × 53.98 mm (ISO/IEC 7810)

Questions

Answered plainly.

What size wire for a 20 amp circuit?

12 AWG copper. 240.4(D) caps 12 AWG at a 20 A breaker whatever the table says, and 14 AWG is capped at 15 A. A long run may need 10 AWG for voltage drop: 12 AWG reaches about 56 ft one way at 16 A and 3 %.

How thick is 12 gauge wire?

12 AWG solid copper is 0.0808 inch (2.05 mm). Stranded 12 AWG is about 0.092 inch, and with THHN insulation about 0.130 inch (3.3 mm) across the jacket.

What does a higher gauge number mean?

A thinner wire. AWG counts drawing steps, so 18 AWG is thinner than 12 AWG; each 6 steps halves the diameter. Above 1 AWG the scale continues as 1/0, 2/0, 3/0 and 4/0, then kcmil.

What size wire for a 48 amp EV charger?

6 AWG copper THHN in conduit on a 60 A breaker (3/4" EMT), or 4 AWG NM-B in the wall. The charger is continuous, so the circuit must be 125 % of 48 A.

Can I measure wire on my phone screen?

Yes, once the screen is calibrated with a coin or a card. Lay the stripped wire along the caliper lines and close the jaw until it just fills the gap. Below about 24 AWG a pixel is too coarse; wind 10 turns on a pencil and measure the coil instead.

Is the gauge the same for copper and aluminum?

The diameters are the same, the ampacity is not. Aluminum carries about 78 % of copper’s current at the same size, so it is used a size or two larger: a 100 A feeder is 3 AWG copper or 1 AWG aluminum.

Wire gauge chart & 1:1 screen sizer

The answer

How it was worked out

6 AWG

Wire gauge reference 67 rows

AWG wire gauge chart: diameter, area, resistance and ampacity

NEC Table 310.16 ampacity, copper

Metric wire sizes (mm²) to AWG

Copper first,then the code.

The AWG formula

Three answers for the same wire

Why the screen can be trusted

Answered plainly.

What size wire for a 20 amp circuit?

How thick is 12 gauge wire?

What does a higher gauge number mean?

What size wire for a 48 amp EV charger?

Can I measure wire on my phone screen?

Is the gauge the same for copper and aluminum?

Browse all 20 gauges, 12 conduit sizes and 10 circuits

Copper first,
then the code.