AWG 12 wire size, resistance and weight calculator
AWG 12 is defined by the gauge formula, not by a table: the diameter is 0.127 mm times 92 raised to the power (36 - n) / 39. Everything else follows from that and the conductor resistivity.
A rough guide: 3 to 5 A/mm2 for chassis wiring, under 2 for long runs in conduit.
- Diameter
- 2.052 53
- Area in circular mils
- 6.529 95
- Resistance of that length
- 0.521 039 ohm
- Resistance per kilometre
- 5.210 39 ohm/km
- Resistance per 1000 feet
- 1.588 13 ohm
- Weight of that length
- 2.964 66
- Current at the chosen density
- 13.24 A
- Turns per centimetre, close-wound
- 4.872
Show the working
- Length of wire = 100
- Conductor = 1.724e-8
- Conductor temperature = 20
- Conductor density = 8960
- Design current density = 4
- Diameter = 0.127 * 92^((36 - (12)) / 39) = 2.052 53
- diameter_in = 2.052 53 / 25.4 = 0.080 808 1
- Cross-sectional area = pi * 2.052 53^2 / 4 = 3.308 77
- Area in circular mils = 0.080 808 1^2 * 1000 = 6.529 95
- r_per_m_20 = 1.724e-8 / (3.308 77 * 1e-6) = 0.005 210 39
- r_per_m = 0.005 210 39 * (1 + 0.00393 * (20 - 20)) = 0.005 210 39
- Resistance of that length = 0.005 210 39 * 100 = 0.521 039
- Resistance per kilometre = 0.005 210 39 * 1000 = 5.210 39
- Resistance per 1000 feet = 0.005 210 39 * 304.8 = 1.588 13
- Weight of that length = 3.308 77 * 1e-6 * 100 * 8960 = 2.964 66
- Current at the chosen density = 3.308 77 * 4 = 13.2351
- Turns per centimetre, close-wound = 2.052 53 > 0 ? 10 / 2.052 53 : 0 = 4.872 05
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- diameter in mm = 0.127 x 92^((36 - n)/39)
- area = pi d^2 / 4
- resistance = rho x length / area
- temperature correction: R(T) = R(20) x (1 + 0.00393 (T - 20)) for copper
The gauge formula is exact: 36 AWG is 0.127 mm and 0000 AWG is 11.684 mm, with 39 steps between them in a geometric progression of ratio 92^(1/39).
The current figure is a design rule of thumb from current density, not an ampacity rating. Real ampacity depends on insulation temperature rating, bundling, ambient temperature and the wiring code in force.
Aluminium conductors of the same gauge carry about 61% of the current of copper for the same heating.
Frequently asked
What is the diameter of AWG 12 wire?
It follows from the gauge definition: 0.127 mm x 92^((36 - n)/39). The calculator shows the result in millimetres and inches.
Why does the wire gauge number go down as the wire gets thicker?
The number counts drawing operations. Each pass through a die makes the wire thinner and adds one to the gauge, so a high number means a thin wire.