Conversion chart
mm² to AWG conversion chart
Metric cable is sold by cross-sectional area in mm², North American wire by AWG or kcmil. This page converts between the two, shows how far apart the nearest sizes actually are, and explains why a size conversion is not the same thing as a current-rating equivalence. Calculators that take a conductor size show both AWG and mm². Box fill allowances stay tabulated by AWG, with the metric area shown beside the gauge.
Metric size to the nearest AWG/kcmil
The metric column is the nominal size as sold. The AWG column is the closest standard size by cross-sectional area, and the last column shows how much larger or smaller it is.
| Metric size | Nearest AWG/kcmil | Its actual area | Difference |
|---|---|---|---|
| 1.5 mm² | 16 AWG | 1.31 mm² | -12.8 % |
| 2.5 mm² | 14 AWG | 2.08 mm² | -16.7 % |
| 4 mm² | 12 AWG | 3.31 mm² | -17.3 % |
| 6 mm² | 10 AWG | 5.26 mm² | -12.3 % |
| 10 mm² | 8 AWG | 8.37 mm² | -16.3 % |
| 16 mm² | 6 AWG | 13.3 mm² | -16.9 % |
| 25 mm² | 3 AWG | 26.66 mm² | +6.7 % |
| 35 mm² | 2 AWG | 33.63 mm² | -3.9 % |
| 50 mm² | 1/0 AWG | 53.51 mm² | +7 % |
| 70 mm² | 2/0 AWG | 67.44 mm² | -3.7 % |
| 95 mm² | 3/0 AWG | 85.03 mm² | -10.5 % |
| 120 mm² | 250 kcmil | 126.68 mm² | +5.6 % |
| 150 mm² | 300 kcmil | 152.01 mm² | +1.3 % |
| 185 mm² | 350 kcmil | 177.35 mm² | -4.1 % |
| 240 mm² | 500 kcmil | 253.35 mm² | +5.6 % |
| 300 mm² | 600 kcmil | 304.02 mm² | +1.3 % |
Reference: areas are geometric (1 circular mil = 0.0005067075 mm²), converted from the standard size series. Nominal metric sizes are defined by IEC 60228; no current rating is implied by this table.
AWG/kcmil to mm², every size
| Size | mm² | Nearest metric size | Difference |
|---|---|---|---|
| 18 AWG | 0.82 | 0.75 mm² | -8.6 % |
| 16 AWG | 1.31 | 1.5 mm² | +14.7 % |
| 14 AWG | 2.08 | 2.5 mm² | +20 % |
| 12 AWG | 3.31 | 4 mm² | +20.9 % |
| 10 AWG | 5.26 | 6 mm² | +14.1 % |
| 8 AWG | 8.37 | 10 mm² | +19.5 % |
| 6 AWG | 13.3 | 16 mm² | +20.3 % |
| 4 AWG | 21.15 | 25 mm² | +18.2 % |
| 3 AWG | 26.66 | 25 mm² | -6.2 % |
| 2 AWG | 33.63 | 35 mm² | +4.1 % |
| 1 AWG | 42.41 | 35 mm² | -17.5 % |
| 1/0 AWG | 53.51 | 50 mm² | -6.6 % |
| 2/0 AWG | 67.44 | 70 mm² | +3.8 % |
| 3/0 AWG | 85.03 | 95 mm² | +11.7 % |
| 4/0 AWG | 107.22 | 95 mm² | -11.4 % |
| 250 kcmil | 126.68 | 120 mm² | -5.3 % |
| 300 kcmil | 152.01 | 150 mm² | -1.3 % |
| 350 kcmil | 177.35 | 185 mm² | +4.3 % |
| 400 kcmil | 202.68 | 185 mm² | -8.7 % |
| 500 kcmil | 253.35 | 240 mm² | -5.3 % |
| 600 kcmil | 304.02 | 300 mm² | -1.3 % |
| 750 kcmil | 380.03 | 400 mm² | +5.3 % |
| 1000 kcmil | 506.71 | 500 mm² | -1.3 % |
Reference: physical geometry only — 1 circular mil = pi/4 x (0.0254 mm)². This is a size conversion, not a rating comparison.
Read this before swapping a size
- A size conversion is not a rating conversion. NEC ampacity values and IEC or BS 7671 current-carrying capacities are built on different assumptions about installation method, insulation and ambient temperature.
- The nearest size is often not a match. The two systems step differently, so the closest equivalent can be 10–25% off in area. The difference column above exists for that reason.
- Insulation changes the outside diameter. Two 2.5 mm² cables with different insulation take different space in a raceway, so conversions by area do not transfer to conduit fill directly.
- Check the standard your installation is inspected against. That is the table that governs, regardless of which unit the cable is sold in.
Frequently asked
- How do I convert mm² to AWG?
- Convert the metric cross-section to circular mils (1 mm² = 1973.5 circular mils), then find the AWG size with the closest circular-mil area. For example 2.5 mm² is 4934 circular mils, which sits closest to 14 AWG at 4110 circular mils. Because the two systems use different size steps, the nearest size is rarely an exact match — the chart on this page shows how far apart they are.
- Is 2.5 mm² the same as 14 AWG?
- No. They are close in area but not identical: 2.5 mm² is about 20% larger than 14 AWG. They are often treated as equivalents in trade conversation, which is fine for rough planning, but the area difference matters once current ratings and voltage drop are calculated.
- Can I use an NEC ampacity table for a metric cable?
- Not directly. NEC ampacity values describe conductors evaluated under that code, and IEC or BS 7671 current-carrying capacities depend on the installation reference method, the insulation and the ambient temperature in ways that do not line up one to one. Use the table that belongs to the standard your installation is inspected against.
Use these sizes in a calculator
One worked example: 3.31 mm² is what a 12 AWG conductor actually measures. The nearest IEC 60228 size is 4 mm², not 2.5 mm². 2.5 mm² is the size people compare with 14 AWG.
Educational information only — not professional engineering advice. Always verify against the standard in force where the installation will be inspected.