Magnet Wire Gauge Explorer

The American Wire Gauge is a geometric series: 39 steps between AWG 36 and AWG 0000, every six gauges halving the diameter. Slide through the gauges to see the wire magnified, its resistance per metre and how much current it may safely carry.

Parameters

Wire gaugeAWG

Allowed current density

J

2–3 for buried windings, 4–6 for open airA/mm²

Temperature

T

°C

Fig. 3AWG 30 magnet wire in section, heavy-build enamel.

AWG 30

Bare diameter

d

0.255 mm

Enamelled Ø

d_i

0.285 mm

Copper area

A

0.0509 mm²

Resistance339 mΩ/m

Per 1000 ft103 Ω

Length per kg2,192 m

Turns / cm35.1

Max current

I_{max}

153 mA

Diameter10 mil

Resistance per metre across the gauge range

Reference table (tap a row)

AWG	Ø bare mm	Ø enam. mm	Ω / m	Turns/cm	I @ J
14	1.63	1.71	0.00828	5.84	6.24 A
15	1.45	1.53	0.0104	6.55	4.95 A
16	1.29	1.36	0.0132	7.34	3.93 A
17	1.15	1.22	0.0166	8.23	3.11 A
18	1.02	1.08	0.0209	9.22	2.47 A
19	0.912	0.968	0.0264	10.3	1.96 A
20	0.812	0.864	0.0333	11.6	1.55 A
21	0.723	0.772	0.042	13	1.23 A
22	0.644	0.69	0.053	14.5	977 mA
23	0.573	0.616	0.0668	16.2	774 mA
24	0.511	0.551	0.0842	18.1	614 mA
25	0.455	0.493	0.106	20.3	487 mA
26	0.405	0.441	0.134	22.7	386 mA
27	0.361	0.395	0.169	25.3	306 mA
28	0.321	0.354	0.213	28.3	243 mA
29	0.286	0.317	0.268	31.5	193 mA
30	0.255	0.285	0.339	35.1	153 mA
31	0.227	0.256	0.427	39.1	121 mA
32	0.202	0.23	0.538	43.5	96.1 mA
33	0.18	0.207	0.679	48.3	76.2 mA
34	0.16	0.187	0.856	53.6	60.4 mA
35	0.143	0.168	1.08	59.4	47.9 mA
36	0.127	0.152	1.36	65.8	38 mA
37	0.113	0.138	1.72	72.7	30.1 mA
38	0.101	0.125	2.16	80.2	23.9 mA
39	0.0897	0.113	2.73	88.3	19 mA
40	0.0799	0.103	3.44	97	15 mA
41	0.0711	0.094	4.34	106	11.9 mA
42	0.0633	0.0859	5.47	116	9.45 mA
43	0.0564	0.0787	6.9	127	7.5 mA
44	0.0502	0.0722	8.7	138	5.95 mA

How it works

Theory · assumptions · formulas

The geometric series

AWG was defined by fixing gauge 36 at 0.005 inch and gauge 0000 at 0.46 inch, with 39 equal ratios in between:

d_n = 0.127\ \mathrm{mm} \times 92^{\frac{36-n}{39}}

Each step changes the diameter by $92^{1/39} \approx 1.1229$ and the area by about 1.261. Three gauges therefore double the area (halve the resistance), and six gauges halve the diameter.

Resistance and mass

\frac{R}{\ell} = \frac{\rho_T}{A}, \qquad \frac{\ell}{m} = \frac{1}{\delta_{Cu}\,A}

with $\delta_{Cu} = 8960\ \mathrm{kg/m^3}$ . Magnet wire is bought by weight, so the length per kilogram tells you how many spools a winding will consume.

Current rating

The safe current is set by heating, not by the wire itself. Expressed as a current density $I_{max} = J\,A$ : an inner layer buried in a thick coil can only shed heat through the layers above it, so 2–3 A/mm² is typical for field coils; single-layer windings in free air tolerate much more.

Enamel thicknessThe enamelled diameter uses the approximation

d_i \approx 1.04\,d + 20\,\mu\mathrm{m}

, close to heavy-build (grade 2) wire. Single-build wire is slimmer; triple-build fatter. Check the manufacturer's data for precise winding counts.