Wire Gauge Calculator

Created by Luis Hoyos
Last updated: Nov 05, 2022

This wire gauge calculator calculates the wire diameter, cross-sectional area, and resistance per unit length, given the AWG or SWG number. It works as an AWG calculator and SWG calculator.

In the rest of this article, we talk a bit more about:

  • The different wire gauges the calculator uses;
  • How to determine the wire gauges using the formulas and charts; and
  • How to calculate wire resistance per unit length.

🔎 If you still don't know the required wire size, use our wire size calculator for the AWG that results optimal for your project. If it's only a direct current (DC) system, we also have a dedicated DC wire size calculator.

How to calculate wire gauge

American wire gauge

American wire gauge (AWG) is a standardized wire gauge system used for the diameters of round, solid, nonferrous, electrically conducting wires. The AWG system consists of grades numbered from 0 to 40. The higher the grade number, the smaller the diameter of the wire. For example, a 12 AWG wire has a thicker diameter than a 14 AWG wire.

The formula for determining the diameter of an AWG number, nn, is as follows:

 ⁣diameter (in) ⁣ ⁣= ⁣0.005 in ⁣× ⁣9236n39 ⁣diameter (mm) ⁣ ⁣= ⁣0.127 mm ⁣× ⁣9236n39\small \begin{align*} \!\text{diameter (in)} &\!\!=\! 0.005\ \text{in}\! \times \!92^{\frac{36-n}{39}}\\ \!\text{diameter (mm)} &\!\!=\! 0.127\ \text{mm}\! \times \!92^{\frac{36-n}{39}} \end{align*}

For example, to calculate the diameter of a 36 AWG, we input n=36n = 36 in the previous formula; for AWG 1, we input n=1n = 1; and so on. The only exceptions are the lower gage numbers, in which we use the following nn values:

A ⁣W ⁣G  0 (1/0)n=0A ⁣W ⁣G  00 (2/0)n=1A ⁣W ⁣G  000 (3/0)n=2A ⁣W ⁣G  0000 (4/0)n=3\small \begin{align*} \text{A\!W\!G}\ \ 0\ (1/0) &\rightarrow n = 0 \\ \text{A\!W\!G}\ \ 00\ (2/0) &\rightarrow n = -1 \\ \text{A\!W\!G}\ \ 000\ (3/0) &\rightarrow n = -2 \\ \text{A\!W\!G}\ \ 0000\ (4/0) &\rightarrow n = -3 \\ \end{align*}

Standard wire gauge

The Standard wire gauge (SWG) is another standardized wire gauge system. It's not so popular these days, but it is still present when defining the thickness of guitar strings and some types of electrical wiring.

SWG doesn't follow an exact relationship like the one provided by the previous AWG formula (although some approximations exist). To obtain the diameter of a particular SWG, you need to look it up in a gauge chart:

SWG Gauge

Diameter (in)

Diameter (mm)

7/0

0.5

12.7

6/0

0.464

11.786

5/0

0.432

10.973

4/0

0.4

10.16

3/0

0.372

9.449

2/0

0.348

8.839

0

0.324

8.23

1

0.3

7.62

2

0.276

7.01

3

0.252

6.401

4

0.232

5.893

5

0.212

5.385

6

0.192

4.877

7

0.176

4.47

8

0.16

4.064

9

0.144

3.658

10

0.128

3.251

11

0.116

2.946

12

0.104

2.642

13

0.092

2.337

14

0.08

2.032

15

0.072

1.829

16

0.064

1.626

17

0.056

1.422

18

0.048

1.219

19

0.04

1.016

20

0.036

0.914

21

0.032

0.813

22

0.028

0.711

23

0.024

0.61

24

0.022

0.559

25

0.02

0.508

26

0.018

0.4572

27

0.0164

0.4166

28

0.0148

0.3759

29

0.0136

0.3454

30

0.0124

0.315

31

0.0116

0.2946

32

0.0108

0.2743

33

0.01

0.254

34

0.0092

0.2337

35

0.0084

0.2134

36

0.0076

0.193

37

0.0068

0.1727

38

0.006

0.1524

39

0.0052

0.1321

40

0.0048

0.1219

41

0.0044

0.1118

42

0.004

0.1016

43

0.0036

0.0914

44

0.0032

0.0813

45

0.0028

0.0711

46

0.0024

0.061

47

0.002

0.0508

48

0.0016

0.0406

49

0.0012

0.0305

50

0.001

0.0254

Cross-sectional area

Once you know the wire diameter, you can calculate the cross-sectional area using the formula to calculate the area of a circle in terms of diameter (dd):

A=π4d2\small A = \frac{\pi}{4}d^2

Electrical resistance per unit length

The equation for the electrical resistance per unit length relies on the resistance-resistivity relationship found in our wire resistance calculator:

R=ρLA\small R = \frac{\rho L}{A}

, where:

  • RR — Resistance, in ohms ΩΩ;
  • LL — Wire's length, in meters (m\text m);
  • ρ\rho — Material's resistivity, in ΩmΩ \cdot \text m; and
  • AA — Cross-section area, in m2\text m^{2};

Rearranging for R/LR/L in the previous equation, we obtain the resistance per unit length:

Resistance per unit length=ρA\small \text{Resistance per unit length} = \frac{\rho}{A}

So, to obtain the resistance per unit length, we need to know the resistivity of the material and the cross-sectional area (obtained with the wire gauge calculator).

Luis Hoyos
Gauge type
American Wire Gauge (AWG)
American wire gauge
0 (1/0)
AWG
Wire material (@ 20 °C)
Copper
Diameter
in
Cross-sectional area
in²
Resistance per length
0.09576
Ω/
kft
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