AWG to mm² and mm² to AWG Wire Gauge Converter
How the formula works
AWG (American Wire Gauge) is a size system where a larger number means a thinner wire. The sizes follow a fixed mathematical rule, so conversion to mm² is exact.
Formulas
Diameter (mm) = 0.127 × 92(36 − n) / 39
Area (mm²) = π / 4 × Diameter²
Area (kcmil) = (Diameter in mil)² / 1000, where 1 mm = 39.37 mil
For mm² to AWG: n = 36 − 39 × ln(Diameter / 0.127) / ln(92)
Resistance (ohm/km) = Resistivity / Area, with 17.241 for copper and 28.26 for aluminium at 20 °C
Where:
- n = AWG number (1/0 is 0, 2/0 is −1, 3/0 is −2 and 4/0 is −3)
- 1 kcmil (MCM) = 0.5067 mm²
- 1 ohm/km = 0.3048 ohm per 1,000 ft
Typical values
14 AWG is about 2.08 mm², 12 AWG is 3.31 mm², 10 AWG is 5.26 mm², 8 AWG is 8.37 mm², 6 AWG is 13.3 mm² and 4/0 AWG is 107.2 mm². The nearest metric sizes used are 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400 and 500 mm². These are the true AWG values. Metric and AWG sizes are never exactly equal, so check the current rating in the code you follow.
How to use the calculator: choose the calculation and the material, select the AWG size or enter the area in mm², then click Calculate.
Important notes: current rating depends on insulation, installation and the local code. Do not select a cable only by area.
Worked example
Example 1: 10 AWG to mm²
Diameter = 0.127 × 9226/39 = 2.588 mm. Area = 5.261 mm² (10.38 kcmil). The nearest metric size is 6 mm². Copper resistance = 3.277 ohm/km (0.999 ohm per 1,000 ft).
Example 2: 14 AWG to mm²
Diameter = 1.628 mm. Area = 2.081 mm² (4.11 kcmil). The nearest metric size is 2.5 mm². Copper resistance = 8.285 ohm/km.
Example 3: 4/0 AWG to mm²
Diameter = 11.684 mm. Area = 107.219 mm² (211.6 kcmil). The nearest metric size is 120 mm². Copper resistance = 0.161 ohm/km.
Example 4: 2.5 mm² to AWG
Diameter = 1.784 mm, so n = 13.2. The nearest size is 13 AWG (2.624 mm²), which is 5.0 % larger. The next smaller size is 14 AWG (2.081 mm²).
Example 5: 16 mm² to AWG
Diameter = 4.514 mm, so n = 5.2. The nearest size is 5 AWG (16.773 mm²), which is 4.8 % larger. The next smaller size is 6 AWG (13.302 mm²).
Example 6: 150 mm² (above 4/0)
Diameter = 13.82 mm. This is larger than 4/0 AWG (107.2 mm²), so the equivalent is 296 kcmil (MCM).
Common mistakes
- Thinking a larger AWG number means a thicker wire. It is the opposite.
- Using 1/0 and 10 as the same size. 1/0 AWG is very large, and 10 AWG is small.
- Assuming AWG and metric sizes are exactly equal, and choosing 2.5 mm² as 14 AWG without checking.
- Selecting a smaller size when the nearest AWG is below the required area.
- Using the area to decide the current rating, without checking insulation, temperature and the code.
- Mixing up kcmil (MCM) with mm². 1 kcmil is only 0.5067 mm².
- Forgetting that stranded wire has a larger outside diameter than solid wire of the same area.
- Using the AWG diameter as the diameter of the insulated cable.
- Ignoring the higher resistance of aluminium when converting copper sizes.
Frequently asked questions
How do I convert AWG to mm²?
Find the diameter with 0.127 × 92^((36 − n) / 39) mm, then area = π / 4 × diameter².
What is 10 AWG in mm²?
10 AWG is 5.26 mm², with a diameter of 2.588 mm.
What is 12 AWG in mm²?
12 AWG is 3.31 mm², with a diameter of 2.053 mm.
What is 14 AWG in mm²?
14 AWG is 2.08 mm², which is close to 2.5 mm².
How do I convert mm² to AWG?
Find the diameter from the area, then use n = 36 − 39 × ln(d / 0.127) / ln(92) and round to the nearest whole AWG.
Is a larger AWG number thicker or thinner?
Thinner. 4 AWG is thicker than 10 AWG.
What do 1/0, 2/0, 3/0 and 4/0 mean?
They are sizes above 1 AWG, called one-naught to four-naught. 4/0 AWG (also written 0000) is 107.2 mm².
What is kcmil or MCM?
It is 1,000 circular mils. It is used for sizes above 4/0 AWG. 1 kcmil is 0.5067 mm².
Is 2.5 mm² the same as 14 AWG?
No. 14 AWG is 2.08 mm². A 2.5 mm² wire is close to 13 AWG (2.62 mm²).
How much current can a wire carry?
It depends on insulation, temperature, installation and the code. Use the Cable Size Calculator for a size by current and voltage drop.
How do I find the voltage drop of a cable?
Use the resistance in ohm/km from this page with your current and length, or use the Voltage Drop Calculator.
Is the conversion exact?
The AWG to mm² conversion follows the standard formula. The nearest metric size is only a guide.