12 AWG vs 14 AWG
| 12 AWG | 14 AWG | |
|---|---|---|
| Diameter | 2.053 mm | 1.628 mm |
| Cross-section | 3.31 mm² | 2.08 mm² |
| Resistance (copper) | 5.21 Ω/km | 8.28 Ω/km |
| NEC 60 °C ampacity | 20 A | 15 A |
Which is thicker
12 AWG has 1.59× the copper of 14 AWG in cross-section, and carries current with 37% less resistance per metre. AWG numbers run backwards because the scale counts drawing passes: more passes, thinner wire, higher number.
Voltage lost over a run at 15 A
| One-way run | 12 AWG | 14 AWG |
|---|---|---|
| 10 m (33 ft) | 1.56 V (1.3%) | 2.49 V (2.1%) |
| 20 m (66 ft) | 3.13 V (2.6%) | 4.97 V (4.1%) over 3% |
| 30 m (98 ft) | 4.69 V (3.9%) over 3% | 7.46 V (6.2%) over 3% |
| 50 m (164 ft) | 7.82 V (6.5%) over 3% | 12.43 V (10.4%) over 3% |
Figures are for a 120 V supply and count both conductors, because the current returns along the neutral. 14 AWG stays inside 3% out to about 14 m; 12 AWG reaches 23 m. That gap is the usual reason to upsize a wire the ampacity table already allows.
What each is rated to carry
On the NEC 310.16 60 °C column, 12 AWG copper is rated 20 A and 14 AWG is rated 15 A. Those figures set the breaker, and they are not the whole story: insulation type, ambient temperature, how many conductors share a conduit and your local code all move them. Circuit design is an electrician's call, not a table's.
Frequently asked questions
What is the difference between 12 AWG and 14 AWG?
12 AWG is the thicker wire: 2.053 mm across against 1.628 mm, with 1.59× the cross-section. Thicker copper means lower resistance — 5.21 Ω/km against 8.28 Ω/km — so less voltage is lost along a run.
Can I use 12 AWG instead of 14 AWG?
Going thicker is electrically safe — 12 AWG has less resistance and runs cooler than 14 AWG at the same current. The practical limits are cost, stiffness and whether it fits the terminals. Going the other way, to thinner wire, is the direction that needs the ampacity table and an electrician.
How far can 14 AWG run at 15 A?
About 14 m (46 ft) before the drop reaches 3% of a 120 V supply. 12 AWG reaches 23 m (75 ft) at the same current. The 3% figure is the informational note in NEC 210.19, not a hard rule, but it is the number most designs work to.
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