AWG to mm2 wire gauge converter
Choose an American Wire Gauge to see its exact diameter and cross-section area, or enter an area in mm2 to find the nearest gauge. The tool also shows kcmil and the resistance of copper wire per kilometer.
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How to use it
- Choose AWG to mm2 and pick a gauge, or choose mm2 to AWG and type a cross-section area.
- Read the diameter, area, kcmil and resistance. In the reverse mode the nearest gauge and its fractional number are shown too.
- The current line appears for only a few gauges and is a labelled reference, not installation advice.
How the conversion works
AWG sizes follow a geometric series defined by two reference points: 36 AWG has a diameter of 0.005 in and 0000 AWG has a diameter of 0.460 in, with 39 steps between them. This gives the exact formula d = 0.127 mm x 92^((36 - n)/39). The area is pi/4 x d2. kcmil is the square of the diameter in thousandths of an inch, divided by 1,000. To go from area to gauge the formula is inverted: n = 36 - 39 x ln(d / 0.127) / ln(92), then rounded to the nearest whole gauge.
Worked example
12 AWG: d = 0.127 x 92^(24/39) = 2.0525 mm, which is 0.0808 in. The area is pi/4 x 2.0525 squared = 3.309 mm2, or 6.53 kcmil. Copper resistance is 17.241 / 3.309 = 5.21 ohm per kilometer.
Reference
| AWG |
Diameter (mm) |
Area (mm2) |
| 0000 |
11.684 |
107.2 |
| 10 |
2.588 |
5.26 |
| 12 |
2.053 |
3.31 |
| 14 |
1.628 |
2.08 |
| 36 |
0.127 |
0.0127 |
Wiring work can be dangerous. Choose cable size from your local electrical code and with a qualified person.
Frequently asked questions
What is the AWG diameter formula?
The diameter in millimeters is d = 0.127 x 92^((36 - n) / 39), where n is the gauge number. 36 AWG is defined as 0.005 in (0.127 mm), 0000 AWG as 0.46 in (11.684 mm), and the 39 steps between them form a geometric series. Gauges 00, 000 and 0000 count as n = -1, -2 and -3.
Does a higher AWG number mean a thicker wire?
No, the opposite. The number is the gauge, so a smaller number is a thicker wire. Every 6 gauges the diameter roughly halves, and every 3 gauges the area roughly halves.
Can I use the current figure to choose a cable?
No. It is a typical reference only. It shows the common US limits on overcurrent protection for ordinary copper branch-circuit wire (14 AWG 15 A, 12 AWG 20 A, 10 AWG 30 A). Real ratings depend on insulation, temperature, bundling, length and local code, so follow your electrical code and ask a qualified electrician.
How is the resistance calculated?
It is the resistivity of annealed copper, 0.017241 ohm mm2/m at 20 C (the 100 percent IACS standard), divided by the area, shown per kilometer. Real wire varies slightly, and stranded wire has a larger overall diameter than the solid wire used here.
Why is the nearest AWG for 2.5 mm2 not exact?
Metric cable sizes and AWG are different series. 2.5 mm2 lies between 14 AWG (2.08 mm2) and 13 AWG (2.62 mm2), and the tool gives the nearest gauge and the exact fractional number. The area shown is that of the nearest standard gauge.