AWG 3 wire size, resistance and weight calculator
AWG 3 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
- 5.827 34
- Area in circular mils
- 52.6348
- Resistance of that length
- 0.064 640 8 ohm
- Resistance per kilometre
- 0.646 408 ohm/km
- Resistance per 1000 feet
- 0.197 025 ohm
- Weight of that length
- 23.8967
- Current at the chosen density
- 106.68 A
- Turns per centimetre, close-wound
- 1.716
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 - (3)) / 39) = 5.827 34
- diameter_in = 5.827 34 / 25.4 = 0.229 423
- Cross-sectional area = pi * 5.827 34^2 / 4 = 26.6705
- Area in circular mils = 0.229 423^2 * 1000 = 52.6348
- r_per_m_20 = 1.724e-8 / (26.6705 * 1e-6) = 0.000 646 408
- r_per_m = 0.000 646 408 * (1 + 0.00393 * (20 - 20)) = 0.000 646 408
- Resistance of that length = 0.000 646 408 * 100 = 0.064 640 8
- Resistance per kilometre = 0.000 646 408 * 1000 = 0.646 408
- Resistance per 1000 feet = 0.000 646 408 * 304.8 = 0.197 025
- Weight of that length = 26.6705 * 1e-6 * 100 * 8960 = 23.8967
- Current at the chosen density = 26.6705 * 4 = 106.682
- Turns per centimetre, close-wound = 5.827 34 > 0 ? 10 / 5.827 34 : 0 = 1.716 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 3 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.