AWG 31 wire size, resistance and weight calculator
AWG 31 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
- 0.226 763
- Area in circular mils
- 0.079 703 1
- Resistance of that length
- 42.6879 ohm
- Resistance per kilometre
- 426.879 ohm/km
- Resistance per 1000 feet
- 130.113 ohm
- Weight of that length
- 0.036 186
- Current at the chosen density
- 0.16 A
- Turns per centimetre, close-wound
- 44.099
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 - (31)) / 39) = 0.226 763
- diameter_in = 0.226 763 / 25.4 = 0.008 927 66
- Cross-sectional area = pi * 0.226 763^2 / 4 = 0.040 386 2
- Area in circular mils = 0.008 927 66^2 * 1000 = 0.079 703 1
- r_per_m_20 = 1.724e-8 / (0.040 386 2 * 1e-6) = 0.426 879
- r_per_m = 0.426 879 * (1 + 0.00393 * (20 - 20)) = 0.426 879
- Resistance of that length = 0.426 879 * 100 = 42.6879
- Resistance per kilometre = 0.426 879 * 1000 = 426.879
- Resistance per 1000 feet = 0.426 879 * 304.8 = 130.113
- Weight of that length = 0.040 386 2 * 1e-6 * 100 * 8960 = 0.036 186
- Current at the chosen density = 0.040 386 2 * 4 = 0.161 545
- Turns per centimetre, close-wound = 0.226 763 > 0 ? 10 / 0.226 763 : 0 = 44.099
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
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 31 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.