Wire Gauge Converter

How to use Wire Gauge Converter

1. Enter an AWG number, or a diameter or area in metric.
2. Read the equivalents in the other units.
3. Use a code-compliant ampacity table — not this — to choose a wire for a real circuit.
4. Higher gauge numbers mean thinner wire; 4/0 is written 0000 and is the thickest common size.
5. Every 6 gauges roughly doubles or halves the diameter; every 3 gauges does the same to area.
6. This gives dimensions only — safe current depends on insulation, ambient temperature, bundling and run length.

Why the numbers run backwards

AWG counts drawing operations: wire is pulled through progressively smaller dies, and the gauge number is how many times it was drawn. More draws means thinner wire, so a higher number is a smaller conductor. 4/0 (written 0000) is the thickest in common use and 40 AWG is hair-fine. The scale is logarithmic — every 6 gauges roughly halves or doubles the diameter, and every 3 gauges halves or doubles the cross-sectional area, which is a useful pair of rules to carry.

Area is what carries current, not diameter

Current capacity scales with cross-sectional area, and area goes as the square of diameter. So a wire twice the diameter carries roughly four times the current, and the 3-gauge rule above is the practical form of that. Metric cable is specified directly in mm² for the same reason, which makes it the more transparent system — AWG 12 is 3.31 mm², and the metric label tells you that without a conversion.

Ampacity depends on far more than the wire

A gauge does not have a single safe current. It depends on insulation temperature rating, ambient temperature, whether the conductor is in free air or bundled in a conduit with others, the length of the run, and whether the load is continuous. Electrical codes — the NEC in the US, BS 7671 in the UK, and their equivalents elsewhere — set the figures, and they include derating tables for exactly these conditions. This converter gives you dimensions, not a current rating.

Voltage drop is what actually sizes a long run

Over distance, resistance causes voltage drop, and a wire adequate for the current can still be too thin for the length. The usual design target is under 3% drop for a branch circuit, and long runs — a shed, an outbuilding, low-voltage lighting — are routinely sized up by several gauges for that reason alone. Twelve-volt systems are the worst case, because the same absolute drop is a far larger proportion of the supply.