Wire Gauge Converter
By KAMP Inc. / UnitOwl · Last reviewed:
Wire gauge is an indirect measurement system where larger gauge numbers indicate thinner wires — a counterintuitive convention that trips up both beginners and experienced tradespeople. The American Wire Gauge (AWG) system dominates in North America, while metric cross-sectional area (mm²) is standard in most of the world. Choosing the wrong gauge can cause resistive heating, voltage drop, code violations, or fire hazards, making accurate gauge selection one of the most safety-critical electrical decisions.
Popular Wire Gauge Conversions
AWG: Why Bigger Numbers Mean Thinner Wire
The American Wire Gauge system was formalized in 1857 and is based on the number of drawing steps required to produce the wire from a standard stock. Each AWG step corresponds to approximately a 20.7% reduction in diameter and roughly a 50% reduction in cross-sectional area. The relationship is mathematically defined: diameter (mm) = 0.127 × 92^((36−AWG)/39). AWG 0, 00, 000, and 0000 (written 1/0, 2/0, 3/0, 4/0) are used for very large cables. AWG 40 is extremely fine wire (0.079 mm diameter) used in precision electronics. AWG 10 is about 2.59 mm (commonly used for 30A circuits); AWG 14 is 1.63 mm (15A circuits); AWG 22 is 0.64 mm (low-voltage electronics).
| AWG Size | Diameter / Area / Ampacity |
|---|---|
| AWG 4/0 (0000) | 11.68 mm / 107 mm² / 230A max |
| AWG 2 | 6.54 mm / 33.6 mm² / 95A |
| AWG 6 | 4.11 mm / 13.3 mm² / 55A |
| AWG 10 | 2.59 mm / 5.26 mm² / 30A |
| AWG 12 | 2.05 mm / 3.31 mm² / 20A |
| AWG 14 | 1.63 mm / 2.08 mm² / 15A |
Metric Wire: Cross-Sectional Area in mm²
Outside North America, wire is specified by its cross-sectional area in square millimeters (mm²). Common European and IEC sizes include 1.5 mm², 2.5 mm², 4 mm², 6 mm², 10 mm², 16 mm², and 25 mm². To convert AWG to mm²: mm² = (AWG diameter in mm)² × π/4. AWG 14 ≈ 2.08 mm²; AWG 12 ≈ 3.31 mm²; AWG 10 ≈ 5.26 mm². The closest standard metric sizes would be 2.5 mm² (≈ AWG 13), 4 mm² (≈ AWG 11), and 6 mm² (≈ AWG 9). Note that ampacity (current-carrying capacity) depends not just on wire size but also on insulation type, installation method, ambient temperature, and whether conductors are bundled.
Voltage Drop and Wire Length
Voltage drop increases with wire length and current, and decreases with larger wire cross-section. For DC circuits: Vdrop = (2 × length × current × resistance per unit length). Copper at 20°C has a resistivity of 1.724 × 10⁻⁸ Ω·m. AWG 12 wire has a resistance of about 5.21 Ω per 1,000 feet (17.1 Ω/km); AWG 10 is about 3.28 Ω per 1,000 feet. NEC code limits voltage drop to 3% for branch circuits and 5% total for feeder plus branch. For a 20A, 120V circuit with AWG 12 wire running 50 feet each way (100 feet total): Vdrop = 100 × 20 × 0.00521 = 10.42V — an 8.7% drop, well over code. AWG 8 wire would be needed to meet the 3% limit for this run.
Sources & References
- NIST — Units and Conversion Factors — Official unit conversion factors from the National Institute of Standards and Technology.
- BIPM — The International System of Units (SI) — International SI unit definitions from the International Bureau of Weights and Measures.