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AWG wire gauge chart and calculator

Look up the diameter, cross-section, resistance and mass of any size in this AWG wire gauge chart and calculator, or find the AWG closest to a metric wire. Values follow the NBS copper and aluminum wire tables, with the current limits NASA publishes for wire in flight hardware.

Start from

Examples

Wire gauge (AWG)

Conductor

Conductor temperature

°C

Resistance is tabulated at 20 °C. NEC voltage drop work uses 75 °C.

Stranded (adds 2 % resistance up to 2000 kcmil)

Current

Optional: drop and heat per meter, and current density.

24 AWG diameter

0.5105 mm

Diameter: 0.5105 mm
Diameter in mils: 20.1 mil
Cross-section: 0.2047 mm²
Cross-section in kcmil: 0.404 kcmil
Resistance at 20 °C: 84.22 Ω/km
Per 1000 ft at 20 °C: 25.67 Ω/1000 ft
Mass: 1.82 kg/km
Before ASTM rounding: 0.51056 mm d = 0.127 mm × 92^((36−n)/39)
Derated current, single wire: 3.3 A NASA table 4A
Derated current, bundled: 2 A NASA table 4A

The derated currents are NASA GSFC limits for 200 °C insulated wire in hard vacuum at up to 70 °C ambient. NASA uses 80 % of them for 150 °C wire and 70 % for 135 °C wire, so lower-rated insulation needs less. They are not NEC ampacities; use NEC table 310.16 or the cable maker’s rating for building wiring.

Nearby gauges at 20 °C (annealed copper)

AWG	Diameter	Area	Resistance	Per 1000 ft
21	0.724 mm	0.4116 mm²	41.89 Ω/km	12.77 Ω
22	0.643 mm	0.3243 mm²	53.16 Ω/km	16.2 Ω
23	0.574 mm	0.2588 mm²	66.62 Ω/km	20.31 Ω
24	0.511 mm	0.2047 mm²	84.22 Ω/km	25.67 Ω
25	0.455 mm	0.1624 mm²	106.2 Ω/km	32.37 Ω
26	0.404 mm	0.1281 mm²	134.6 Ω/km	41.02 Ω
27	0.361 mm	0.1022 mm²	168.7 Ω/km	51.43 Ω

How do you find the diameter of an AWG wire?

Use d = 0.127 mm × 92^((36 − n) / 39), then round as ASTM B 258 prescribes. 24 AWG is 0.5105 mm (20.1 mil), which gives a cross-section of 0.2047 mm² and 84.22 Ω/km of copper at 20 °C. Every three gauge numbers down doubles the area and halves the resistance.

AWG formula

The gauge is defined by two diameters: No. 0000 is 0.4600 in and No. 36 is 0.0050 in, with 38 sizes between them in geometric progression.

d = 0.127 mm × 92^((36 − n) / 39)

d: diameter before rounding, in mm
n: gauge number: 1 to 56, 0 for 1/0, −1 for 2/0, −2 for 3/0, −3 for 4/0

ASTM B 258 rounds the result to the nearest 0.1 mil for gauges 0000 to 44 and 0.01 mil for 45 to 56, and those rounded numbers are the commercial sizes. The AWG calculator uses them, so its values match the NBS tables. The largest effect is at the thin end: 40 AWG is 3.145 mil before rounding and 3.1 mil after.

A = (π / 4) × d² R per km = (1000 × ρ20 / A) × (1 + α20 × (T − 20))

A: cross-section in mm²
ρ20: resistivity at 20 °C: 1/58 Ω·mm²/m for annealed copper, 0.028264 for EC-H19 aluminum
α20: temperature coefficient at 20 °C: 0.00393 per °C for copper, 0.00403 for aluminum
T: conductor temperature in °C

The area in circular mils is the diameter in mils squared. One kcmil is 1000 circular mils, and 1 mm² is 1.974 kcmil.

Worked examples

Example 1: properties of 14 AWG

The formula gives 64.08 mil, which rounds to 64.1 mil or 1.628 mm. The cross-section is 2.082 mm². Copper at 20 °C is 1000 ÷ (58 × 2.082) = 8.281 Ω/km, or 2.524 Ω per 1000 ft. At 75 °C it is 10.07 Ω/km.

Example 2: the AWG for a metric wire

35 mm² is a fractional gauge of 1.828, so the nearest AWG is 2 AWG (33.62 mm²). That has less copper than the metric wire; the thinnest gauge with at least 35 mm² is 1 AWG (42.41 mm²).

Example 3: 5 A in 18 AWG

At 20 °C the wire is 20.95 mΩ per meter, so 5 A drops 105 mV/m and heats it by 0.524 W/m. NASA’s derating allows 9.2 A for a single wire and 5 A in a bundle, so 5 A sits at the bundled limit for 200 °C wire.

AWG wire chart: 4/0 to 40

This American Wire Gauge chart lists nominal sizes (ASTM B 258) with annealed copper at 20 °C. EC-H19 aluminum is 1.639 times the copper resistance at the same size.

AWG	Diameter (mm)	Diameter (mil)	Area (mm²)	Area (kcmil)	Ω/km	Ω/1000 ft	kg/km
0000 (4/0)	11.684	460	107.2	211.6	0.1608	0.04901	953.2
000 (3/0)	10.404	409.6	85.01	167.8	0.2028	0.06182	755.8
00 (2/0)	9.266	364.8	67.43	133.1	0.2557	0.07793	599.5
0 (1/0)	8.252	324.9	53.49	105.6	0.3223	0.09825	475.5
1	7.348	289.3	42.41	83.69	0.4066	0.1239	377
2	6.543	257.6	33.62	66.36	0.5128	0.1563	298.9
3	5.827	229.4	26.67	52.62	0.6466	0.1971	237.1
4	5.189	204.3	21.15	41.74	0.8152	0.2485	188
5	4.620	181.9	16.77	33.09	1.028	0.3134	149
6	4.115	162	13.3	26.24	1.297	0.3952	118.2
7	3.665	144.3	10.55	20.82	1.634	0.4981	93.8
8	3.264	128.5	8.367	16.51	2.061	0.6281	74.38
9	2.906	114.4	6.631	13.09	2.6	0.7925	58.95
10	2.588	101.9	5.261	10.38	3.277	0.9988	46.77
11	2.304	90.7	4.168	8.226	4.136	1.261	37.06
12	2.052	80.8	3.308	6.529	5.212	1.589	29.41
13	1.829	72	2.627	5.184	6.564	2.001	23.35
14	1.628	64.1	2.082	4.109	8.281	2.524	18.51
15	1.450	57.1	1.652	3.26	10.44	3.181	14.69
16	1.290	50.8	1.308	2.581	13.19	4.019	11.62
17	1.151	45.3	1.04	2.052	16.58	5.054	9.244
18	1.024	40.3	0.8229	1.624	20.95	6.386	7.316
19	0.912	35.9	0.653	1.289	26.4	8.047	5.806
20	0.813	32	0.5189	1.024	33.23	10.13	4.613
21	0.724	28.5	0.4116	0.8123	41.89	12.77	3.659
22	0.643	25.3	0.3243	0.6401	53.16	16.2	2.883
23	0.574	22.6	0.2588	0.5108	66.62	20.31	2.301
24	0.511	20.1	0.2047	0.404	84.22	25.67	1.82
25	0.4547	17.9	0.1624	0.3204	106.2	32.37	1.443
26	0.4039	15.9	0.1281	0.2528	134.6	41.02	1.139
27	0.3607	14.2	0.1022	0.2016	168.7	51.43	0.9083
28	0.3200	12.6	0.08044	0.1588	214.3	65.33	0.7152
29	0.2870	11.3	0.0647	0.1277	266.5	81.22	0.5752
30	0.2540	10	0.05067	0.1	340.3	103.7	0.4505
31	0.2261	8.9	0.04014	0.07921	429.6	130.9	0.3568
32	0.2032	8	0.03243	0.064	531.7	162.1	0.2883
33	0.1803	7.1	0.02554	0.05041	675	205.7	0.2271
34	0.1600	6.3	0.02011	0.03969	857.3	261.3	0.1788
35	0.1422	5.6	0.01589	0.03136	1085	330.7	0.1413
36	0.1270	5	0.01267	0.025	1361	414.8	0.1126
37	0.1143	4.5	0.01026	0.02025	1680	512.2	0.09122
38	0.1016	4	0.008107	0.016	2127	648.2	0.07207
39	0.0889	3.5	0.006207	0.01225	2778	846.6	0.05518
40	0.0787	3.1	0.004869	0.00961	3541	1079	0.04329

mm² to AWG: metric wire sizes

IEC 60228 nominal sizes with the nearest AWG and the thinnest AWG that has at least the same copper. Use the “At least this area” column when the wire must not be smaller.

Metric size	Nearest AWG	Nearest area	At least this area	Area of that size
0.5 mm²	20 AWG	0.5189 mm²	20 AWG	0.5189 mm²
0.75 mm²	18 AWG	0.8229 mm²	18 AWG	0.8229 mm²
1 mm²	17 AWG	1.04 mm²	17 AWG	1.04 mm²
1.5 mm²	15 AWG	1.652 mm²	15 AWG	1.652 mm²
2.5 mm²	13 AWG	2.627 mm²	13 AWG	2.627 mm²
4 mm²	11 AWG	4.168 mm²	11 AWG	4.168 mm²
6 mm²	9 AWG	6.631 mm²	9 AWG	6.631 mm²
10 mm²	7 AWG	10.55 mm²	7 AWG	10.55 mm²
16 mm²	5 AWG	16.77 mm²	5 AWG	16.77 mm²
25 mm²	3 AWG	26.67 mm²	3 AWG	26.67 mm²
35 mm²	2 AWG	33.62 mm²	1 AWG	42.41 mm²
50 mm²	1/0 AWG	53.49 mm²	1/0 AWG	53.49 mm²
70 mm²	2/0 AWG	67.43 mm²	3/0 AWG	85.01 mm²
95 mm²	3/0 AWG	85.01 mm²	4/0 AWG	107.2 mm²

Derated current by gauge

NASA EEE-INST-002 table 4A. These are limits for 200 °C insulated copper wire in hard vacuum at up to 70 °C ambient. NASA scales them to 80 % for 150 °C wire and 70 % for 135 °C wire.

AWG	Single wire	Bundled or multi-conductor
30 AWG	1.3 A	0.7 A
28 AWG	1.8 A	1 A
26 AWG	2.5 A	1.4 A
24 AWG	3.3 A	2 A
22 AWG	4.5 A	2.5 A
20 AWG	6.5 A	3.7 A
18 AWG	9.2 A	5 A
16 AWG	13 A	6.5 A
14 AWG	19 A	8.5 A
12 AWG	25 A	11.5 A
10 AWG	33 A	16.5 A
8 AWG	44 A	23 A
6 AWG	60 A	30 A
4 AWG	81 A	40 A
2 AWG	108 A	50 A
1/0 AWG	147 A	75 A
2/0 AWG	169 A	87.5 A

What the AWG table leaves out

Current ratings depend on the insulation’s temperature limit, the ambient and how many wires share the bundle, so no single table is right for every use. Vacuum removes convection, which makes NASA’s figures conservative for 200 °C wire in air, but not for wire with a lower temperature rating. Premises wiring in the US follows NEC table 310.16, which is not reproduced here. Stranded wire adds 2 % to resistance (3 to 5 % above 2000 kcmil) and has a larger outer diameter than the solid size, so check the terminal and crimp sizes against the wire’s data sheet. Hard-drawn copper is about 2.5 % more resistive than the annealed copper in these tables, and tin plating adds a little more. AC at high frequency flows near the surface of the conductor, so the DC resistance shown is only the low-frequency limit.

Glossary

AWG: American Wire Gauge, formerly Brown & Sharpe, the North American series of solid round conductor sizes.
Circular mil (cmil): The area of a circle one mil in diameter. A round wire’s area in cmil is its diameter in mils, squared.
kcmil: One thousand circular mils, the unit used for conductors larger than 4/0 AWG. Older documents write MCM.
IACS: International Annealed Copper Standard: 100 % IACS is 1/58 Ω·mm²/m at 20 °C.
Concentric-lay stranding: A central wire surrounded by helical layers of wires, used for flexible and large conductors.
Temperature coefficient: The fractional change of resistance per degree Celsius, 0.00393 for annealed copper at 20 °C.

Related guides

Wire voltage drop calculator: the gauge that keeps a cable run within its budget.
PCB trace width calculator: the same current question for copper on a board.

Frequently asked questions

How do you convert AWG to mm?

Use d = 0.127 mm × 92^((36 − n) / 39), where n is the gauge number (use −1 for 00, −2 for 000 and −3 for 0000). 24 AWG works out to 0.5105 mm after the standard’s rounding.

How do you convert AWG to mm²?

Get the diameter from the AWG formula, then use A = (π / 4) × d². 24 AWG is 0.5105 mm across, so its cross-section is 0.2047 mm².

How do you read an AWG chart?

Find the gauge in the first column and read across for diameter, area, resistance and mass per km. A lower number is a thicker wire: going three gauge numbers lower, which is up the chart, doubles the area and halves the resistance.

What size is 22 AWG in mm²?

0.3243 mm², from a nominal diameter of 25.3 mil (0.6426 mm). Its resistance is 53.16 Ω/km of copper at 20 °C.

Why do bigger AWG numbers mean thinner wire?

The gauge number counts drawing steps: each step pulls the wire through a smaller die, so more steps give a thinner wire. The sizes form a geometric series anchored at 0000 (0.4600 in) and 36 (0.0050 in).

How much does each gauge step change the wire?

Each gauge step changes diameter by a factor of 1.1229. Six steps almost exactly double the diameter (2.005 times), so three steps double the cross-section and halve the resistance, and ten steps change resistance about tenfold.

How much current can 22 AWG carry?

There is no single answer: it depends on the insulation temperature rating, the ambient, and bundling. NASA’s space-flight derating allows 4.5 A for a single 22 AWG wire and 2.5 A in a bundle, for 200 °C wire in vacuum at 70 °C, and 70 % of that for 135 °C wire. Use the wire maker’s rating or NEC table 310.16 for building wiring.

Is this an AWG ampacity chart?

Only in part. The current table here is NASA’s derating for 200 °C insulated copper wire in hard vacuum at up to 70 °C ambient, not a general ampacity rating. For building wiring use the wire maker’s rating or NEC table 310.16, which is not reproduced here.

What is the difference between solid and stranded AWG?

A stranded wire of a given AWG has about the same total copper area as the solid wire, but its outer diameter is larger and its resistance is about 2 % higher because the strands are twisted and so slightly longer.

What AWG is 1.5 mm² wire?

15 AWG (1.652 mm²) is the nearest gauge and has slightly more copper. Odd gauges are less commonly stocked, so in practice use 14 AWG (2.082 mm²), or 16 AWG (1.308 mm²) if a slightly smaller wire is acceptable.

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