Reference › Magnet wire

Magnet Wire Tables

Enameled copper magnet wire, #10 to #40 AWG. Diameters, resistance and area are computed from the AWG definition and copper resistivity, then checked against a NEMA MW 1000 manufacturer table.

Copper magnet wire by AWG

Bare diameter: d = 0.005 in × 92^(36−n)/39. Resistance at 20 °C from annealed copper at 100% IACS, ρ = 1.7241 × 10⁻⁸ Ω·m (10.371 Ω·cmil/ft). Heavy-build overall diameter is the NEMA MW 1000-2020 nominal from MWS Wire's Copper Magnet Wire Data. Turns per inch is computed as 1 ÷ heavy-build diameter, for one close-wound layer.

AWG	Bare (in)	Bare (mm)	Heavy OD (in)	Ω/1000 ft	Ω/km	Area (cmil)	Turns/in (computed)	A at 200 A/cm²*	A at 400 A/cm²*
10	0.1019	2.588	0.105	0.9988	3.277	10,383	9.49	10.5	21.0
11	0.09074	2.305	0.0942	1.260	4.132	8,234	10.6	8.34	16.7
12	0.08081	2.053	0.0842	1.588	5.211	6,530	11.9	6.62	13.2
13	0.07196	1.828	0.0754	2.003	6.571	5,178	13.3	5.25	10.5
14	0.06408	1.628	0.0675	2.525	8.285	4,107	14.8	4.16	8.32
15	0.05707	1.450	0.0603	3.184	10.45	3,257	16.6	3.30	6.60
16	0.05082	1.291	0.0539	4.015	13.17	2,583	18.6	2.62	5.23
17	0.04526	1.150	0.0482	5.063	16.61	2,048	20.7	2.08	4.15
18	0.04030	1.024	0.0431	6.385	20.95	1,624	23.2	1.65	3.29
19	0.03589	0.9116	0.0386	8.051	26.41	1,288	25.9	1.31	2.61
20	0.03196	0.8118	0.0346	10.15	33.31	1,022	28.9	1.04	2.07
21	0.02846	0.7229	0.0310	12.80	42.00	810.1	32.3	0.821	1.64
22	0.02535	0.6438	0.0276	16.14	52.96	642.4	36.2	0.651	1.30
23	0.02257	0.5733	0.0249	20.36	66.78	509.5	40.2	0.516	1.03
24	0.02010	0.5106	0.0223	25.67	84.21	404.0	44.8	0.409	0.819
25	0.01790	0.4547	0.0199	32.37	106.2	320.4	50.3	0.325	0.649
26	0.01594	0.4049	0.0178	40.81	133.9	254.1	56.2	0.258	0.515
27	0.01420	0.3606	0.0161	51.47	168.9	201.5	62.1	0.204	0.408
28	0.01264	0.3211	0.0144	64.90	212.9	159.8	69.4	0.162	0.324
29	0.01126	0.2859	0.0130	81.83	268.5	126.7	76.9	0.128	0.257
30	0.01003	0.2546	0.0117	103.2	338.5	100.5	85.5	0.102	0.204
31	0.008928	0.2268	0.0104	130.1	426.9	79.70	96.2	0.0808	0.162
32	0.007950	0.2019	0.00940	164.1	538.3	63.21	106	0.0641	0.128
33	0.007080	0.1798	0.00840	206.9	678.8	50.13	119	0.0508	0.102
34	0.006305	0.1601	0.00750	260.9	856.0	39.75	133	0.0403	0.0806
35	0.005615	0.1426	0.00670	329.0	1,079	31.52	149	0.0319	0.0639
36	0.005000	0.1270	0.00600	414.8	1,361	25.00	167	0.0253	0.0507
37	0.004453	0.1131	0.00550	523.1	1,716	19.83	182	0.0201	0.0402
38	0.003965	0.1007	0.00490	659.6	2,164	15.72	204	0.0159	0.0319
39	0.003531	0.08969	0.00430	831.8	2,729	12.47	233	0.0126	0.0253
40	0.003145	0.07987	0.00380	1,049	3,441	9.888	263	0.0100	0.0200

*Current at a winding current density, not an ampacity rating. Transformer and inductor designers size windings by current density. McLyman gives the rule of thumb 500 circular mils per amp ≈ 400 A/cm² and 1000 circular mils per amp ≈ 200 A/cm² (Transformer and Inductor Design Handbook, 3rd ed., ch. 4, PDF). The columns are bare copper area × current density, and agree within 3% with the 200 and 400 A/cm² columns of the Magnetics Inc. Wire Table.

Rules of thumb that follow from the AWG formula: every 3 gauges halves the area and doubles the resistance, and every 6 gauges halves the diameter. #10 is about 1 Ω per 1000 ft (MWS: 0.9988 Ω).