Can I use 14 gauge wire on a 20 amp breaker?

Use 12 AWG copper for an ordinary 20 A branch circuit. NEC 240.4(D) caps 14 AWG copper at 15 A, so it cannot be protected by a 20 A breaker for this ordinary use.

How far can I run 12 gauge wire on 20 amps?

12 AWG is the starting answer, but its useful distance depends on voltage and load. Use the dedicated distance guide or enter the exact run in the Wire Size calculator.

What about 20 amps at 240 V?

The ampacity floor stays 12 AWG copper at 20 A, but 240 V gives more voltage-drop room than 120 V. Enter the actual distance and voltage in the Wire Size calculator.

🔌 What Size Wire for a 20 Amp Circuit?

🇨🇦 Canadian version

The short answer

The everyday answer is 12 AWG copper. Do not put 14 AWG copper on a 20 A breaker for an ordinary branch circuit.

NEC 240.4(D) caps 14 AWG copper at 15 A and 12 AWG copper at 20 A for ordinary circuits. A larger raw ampacity in another temperature column does not erase that cap. Ampacity Check tool.

Distance changes the answer

Minimum copper size at 120 V, sized at the full 20 A and kept at or under the 3% voltage-drop target (one-way distance):

20 A at 120 V

Material	50 ft	100 ft	150 ft	200 ft	250 ft	300 ft
Copper	10	8	6	4	4	3

Small-gauge aluminum branch-circuit wire is not shown. Use copper here; check any other wiring method in the Ampacity Check tool. Wire Size calculator.

Common 20-amp jobs

Kitchen small-appliance circuits, bathrooms, garage receptacles, and general lighting are common 20 A jobs. The appliance instructions and local rules still control the final design.

Worked example: 20 A at 120 V over 100 feet

Our verified calculator selects #8 copper (16,510 circular mils): 2 × 12.9 × 20 × 100 ÷ 16,510 = 3.13 V, or 2.6% of 120 V. It passes both the ampacity check and the 3% drop target.

How far can you run 12 gauge wire? · Wire Size calculator · Ampacity Check tool

20-amp wire size FAQ

Can I use 14 gauge wire on a 20 amp breaker?: Use 12 AWG copper for an ordinary 20 A branch circuit. NEC 240.4(D) caps 14 AWG copper at 15 A, so it cannot be protected by a 20 A breaker for this ordinary use.
How far can I run 12 gauge wire on 20 amps?: 12 AWG is the starting answer, but its useful distance depends on voltage and load. Use the dedicated distance guide or enter the exact run in the Wire Size calculator.
What about 20 amps at 240 V?: The ampacity floor stays 12 AWG copper at 20 A, but 240 V gives more voltage-drop room than 120 V. Enter the actual distance and voltage in the Wire Size calculator.