AWG Wire Gauge Table (Diameter, mm², Resistance & Amps)
Look up any AWG size from 18 to 4/0: diameter, cross-section, nearest metric size, resistance and NEC ampacity, on one printable sheet.
AWG Wire Gauge Table: Diameter, Area, Resistance and Ampacity
Use this table to look up a conductor in seconds: American Wire Gauge (AWG) size, bare copper diameter and cross-section in mm², the nearest common metric size, DC resistance at 20°C, and the allowable current (ampacity) for insulated copper conductors from NEC Table 310.16. A bigger AWG number means a thinner wire.
| AWG | Diameter (mm) | Area (mm²) | Nearest metric (mm²) | Resistance (Ω/km) | Resistance (Ω/1000 ft) | 60°C (A) | 75°C (A) | 90°C (A) |
|---|---|---|---|---|---|---|---|---|
| 18 | 1.024 | 0.82 | 1 | 20.95 | 6.385 | – | – | – |
| 16 | 1.291 | 1.31 | 1.5 | 13.17 | 4.015 | – | – | – |
| 14 | 1.628 | 2.08 | 2.5 | 8.28 | 2.525 | 15 | 20 | 25 |
| 12 | 2.053 | 3.31 | 4 | 5.21 | 1.588 | 20 | 25 | 30 |
| 10 | 2.588 | 5.26 | 6 | 3.28 | 0.999 | 30 | 35 | 40 |
| 8 | 3.264 | 8.37 | 10 | 2.06 | 0.628 | 40 | 50 | 55 |
| 6 | 4.115 | 13.30 | 16 | 1.30 | 0.395 | 55 | 65 | 75 |
| 4 | 5.189 | 21.15 | 25 | 0.82 | 0.248 | 70 | 85 | 95 |
| 3 | 5.827 | 26.67 | 25 / 35 | 0.65 | 0.197 | 85 | 100 | 115 |
| 2 | 6.544 | 33.63 | 35 | 0.51 | 0.156 | 95 | 115 | 130 |
| 1 | 7.348 | 42.41 | 50 | 0.41 | 0.124 | 110 | 130 | 145 |
| 1/0 | 8.251 | 53.48 | 50 | 0.32 | 0.098 | 125 | 150 | 170 |
| 2/0 | 9.266 | 67.43 | 70 | 0.26 | 0.078 | 145 | 175 | 195 |
| 3/0 | 10.405 | 85.03 | 95 | 0.20 | 0.062 | 165 | 200 | 225 |
| 4/0 | 11.684 | 107.22 | 120 | 0.16 | 0.049 | 195 | 230 | 260 |
Ampacity: NEC 310.16, copper conductors, 30°C ambient, not more than three current-carrying conductors in a raceway, cable or earth. Resistance: annealed copper at 20°C (1.724 × 10-8 Ω·m), solid conductor. Stranded wire is slightly higher. AWG 18 and 16 are normally used for control, signal and appliance wiring, so no NEC power ampacity is listed here.
How to read the table
Pick the temperature column that matches your weakest part. The three ampacity columns are for insulation rated 60°C, 75°C and 90°C. Even if the wire is rated for 90°C, the breaker or terminal it connects to is often only rated for 60°C or 75°C, and that lower rating decides the usable current. The 90°C column is mainly used as a starting point before derating for heat or bundling.
Small conductors have a breaker limit. In the US, NEC 240.4(D) limits 14 AWG to a 15 A breaker, 12 AWG to 20 A and 10 AWG to 30 A, even though the 90°C column shows higher values for these sizes.
Ampacity is not the only limit. Long runs lose voltage. A wire that is safe for 20 A may still drop too much voltage for a 12 V load 10 m away. Use the voltage drop quick table or the voltage drop calculator to check.
Metric conductor sizes (IEC 60228)
Most of the world outside North America specifies cables by cross-section in mm². These are the maximum DC resistance values for plain copper conductors at 20°C from IEC 60228 (class 2, stranded). Current ratings for metric cables depend heavily on insulation, installation method and local rules (BS 7671, IEC 60364 or your national code), so they are not given here.
| Size | Max resistance (Ω/km) | Loop resistance, 2 wires (Ω/km) |
|---|---|---|
| 1.5 mm² | 12.1 | 24.2 |
| 2.5 mm² | 7.41 | 14.8 |
| 4 mm² | 4.61 | 9.22 |
| 6 mm² | 3.08 | 6.16 |
| 10 mm² | 1.83 | 3.66 |
| 16 mm² | 1.15 | 2.3 |
| 25 mm² | 0.727 | 1.45 |
| 35 mm² | 0.524 | 1.05 |
| 50 mm² | 0.387 | 0.774 |
| 70 mm² | 0.268 | 0.536 |
| 95 mm² | 0.193 | 0.386 |
| 120 mm² | 0.153 | 0.306 |
- Using the 90°C column to size a circuit. Check the terminal rating of the breaker and the device first.
- Forgetting the return conductor. On DC and single-phase circuits the current flows out and back, so the loss is over twice the one-way length.
- Mixing AWG and mm² by name. 12 AWG (3.31 mm²) is not the same as 4 mm². The metric column is only the nearest standard size.
- Ignoring heat and bundling. Hot rooms, conduit in sun and many cables together all lower the allowable current. The cable size calculator applies those correction factors.
Frequently asked questions
What is the diameter of 12 AWG wire? About 2.053 mm, which is a cross-section of 3.31 mm².
How many amps can 10 AWG carry? According to NEC Table 310.16, 30 A (60°C column), 35 A (75°C) or 40 A (90°C) for copper, but it is limited to a 30 A breaker for general circuits.
Is a larger AWG number thicker or thinner? Thinner. 4/0 (0000) AWG is the thickest size in the table and 18 AWG is among the thinnest.
Safety note. These figures are reference values and not a substitute for your local electrical code or a qualified electrician. Always check the code that applies where you are.