Wire Gauge Calculator

Type an AWG label (for example 14, 4/0, AWG 12) or a mm² cross-section (for example 2.5 or 6) and get the diameter, the cross-sectional area in mm² and circular mils, the DC resistance per kilometre and per 1000 feet at 20°C copper, and a chassis-wiring ampacity hint. The reference table below covers AWG 0000 (4/0) through AWG 40 — 44 gauges, the standard set in North American electrical and electronics work. Everything runs in your browser, no upload.

Accepts 14, AWG 12, 1/0, 2/0, 3/0, 4/0, 0000..40.

Type a gauge or area above.

AWG reference table

Copper at 20°C. Click a row to load that gauge into the calculator above. The ampacity hint is the rule-of-thumb amps ≈ cmil / 1000 for chassis wiring in free air at 30°C ambient with PVC insulation — not a regulatory number.

AWG Diameter (mm) Diameter (in) Area (mm²) Area (cmil) Resistance (Ω/km) Resistance (Ω/kft) Ampacity hint (A)
About the AWG standard
  • AWG (American Wire Gauge) is the dominant wire-size standard in North America. The cross-section grows as the gauge number shrinks — AWG 0000 (4/0) is the heaviest at 107.2 mm², AWG 40 the lightest at 0.005 mm².
  • Metric wire in Europe and most of the world is sized by cross-section in mm². Common sizes: 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120 mm². None of these match an AWG exactly; the calculator shows the closest AWG as a hint.
  • Resistance is the DC value at 20°C for copper (resistivity 1.724 × 10⁻⁸ Ω·m). At higher temperatures the resistance rises ~0.4% per °C. AC resistance is higher at high frequency (skin effect) and is not modelled here.
  • Ampacity is application-specific — it depends on insulation rating, ambient temperature, bundling, and the applicable code (NEC, IEC, BS 7671). The hint is the rule of thumb A ≈ cmil / 1000, rounded. Always cross-check with the actual code for your jurisdiction.
  • Voltage drop is V = I × R × length. Multiply the Ω/km by the run length in km and the load current in amps. A common rule for 12 V / 24 V DC systems is to keep the drop below 3% of the system voltage.