This wire gauge calculator converts American Wire Gauge (AWG) to diameter and cross-sectional area, and shows the current a wire can safely carry. Enter a gauge above to get its size in mm and its ampacity.
How is wire gauge calculated?
Diameter (mm) = 0.127 × 92^((36 − n) ÷ 39) Area (mm²) = π ÷ 4 × Diameter²
Where n is the AWG number. A smaller gauge number means a thicker wire.
Common copper wire sizes and ampacity
AWG 14 → 1.63 mm → ~15 A AWG 12 → 2.05 mm → ~20 A AWG 10 → 2.59 mm → ~30 A AWG 8 → 3.26 mm → ~40 A
Ampacity values are a guide for 60°C copper building wire; always size conductors to the NEC and your conditions.
Example
10 AWG: diameter = 0.127 × 92^((36−10)/39) = 2.59 mm, area 5.26 mm², about 30 A.
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Frequently Asked Questions
How do I know what gauge wire I need?
Match the wire’s ampacity to your load. As a guide for copper building wire, 14 AWG handles 15 A, 12 AWG 20 A, and 10 AWG 30 A.
What is 10 gauge wire in mm?
10 AWG is 2.588 mm in diameter with a cross-section of about 5.26 mm2.
How many amps can 12 gauge wire handle?
Copper 12 AWG is rated for about 20 amps in typical residential wiring at 60 C, per NEC guidance.