Electrical Engineering

Wire Gauge / AWG

Look up AWG wire specifications — diameter, resistance, ampacity ratings, and NEC circuit breaker requirements for copper conductors.

Select AWG

2.053 mm

Diameter

3.3100 mm²

Cross-section

5.211 Ω/km

Resistance

20 A

Free-Air Ampacity

NEC Circuit Guide — AWG 12

Max 20A circuit breaker per NEC 310.12 / 240.4(D) for copper in conduit (60°C terminals).

20A circuits — kitchen, bathroom, garage outlets

✓ NEC 240.4(D) explicitly caps AWG 12 at 20A — the breaker must not exceed this even if the terminal rating would allow more.

20A

Max Breaker

In Conduit / Enclosed

20 A

Wires bundled or run through conduit, walls, or enclosures. Heat can't escape freely — lower ampacity. This is the NEC table value used for home and building wiring.

Free Air / Chassis

20 A

Single wire in open air, or internal wiring of equipment (control panels, appliances, machines). Better heat dissipation allows higher current. Not for branch circuit breaker sizing.

Why two ampacity ratings? Ampacity drops when wires are enclosed because heat builds up. NEC Table 310.12 gives the lower conduit values used for sizing breakers in home and commercial wiring.

Quick example: A 12 AWG wire on a 20A breaker is correct — NEC limits 12 AWG to 20A in conduit. Installing it on a 30A breaker would be a code violation and a fire hazard.

Full AWG Reference

Click any row to select. Copper conductors, 60°C insulation rating.

AWG	Diameter	Area	Resistance	In Conduit	Free Air	Max Breaker
AWG 0	8.251	53.4800	0.322	125 A	150 A	125 A
AWG 2	6.544	33.6200	0.513	95 A	95 A	95 A
AWG 4	5.189	21.1500	0.815	70 A	70 A	70 A
AWG 6	4.115	13.3000	1.296	55 A	55 A	55 A
AWG 8	3.264	8.3670	2.061	40 A	40 A	40 A
AWG 10	2.588	5.2610	3.277	30 A	30 A	30 A
AWG 12	2.053	3.3100	5.211	20 A	20 A	20 A
AWG 14	1.628	2.0810	8.286	15 A	15 A	15 A
AWG 16	1.291	1.3090	13.170	13 A	13 A	10 A
AWG 18	1.024	0.8231	20.950	10 A	10 A	7 A
AWG 20	0.812	0.5176	33.310	5 A	7.5 A	—
AWG 22	0.644	0.3255	52.960	3 A	5 A	—
AWG 24	0.511	0.2047	84.220	2 A	3.5 A	—
AWG 26	0.405	0.1288	133.900	1 A	2.2 A	—
AWG 28	0.321	0.0810	212.900	0.5 A	0.8 A	—
AWG 30	0.255	0.0509	338.600	0.3 A	0.5 A	—

Ampacity per NEC Table 310.12 for copper conductors with 60°C-rated terminals, not more than 3 current-carrying conductors in conduit or raceway. Always consult a licensed electrician and your local AHJ (Authority Having Jurisdiction) before any wiring installation.