What Size Wire for a 20 Amp Breaker?
A 20 A breaker needs 12 AWG copper with 75°C terminations (NEC Table 310.16). Longer runs may need a size up for voltage drop: distances below.
Minimum wire size for 20 amps
| Application | Copper (75°C) | Aluminum (75°C) |
|---|---|---|
| Branch circuit / feeder (Table 310.16) | 12 AWG | not typical |
Assumes 75°C-rated terminations (NEC 110.14(C)). Both assume no more than three current-carrying conductors in a raceway at 30°C ambient. Derating, continuous loads, and local amendments can change the answer: confirm with a licensed electrician.
Ground wire for 20 amps
| Ground | Copper | Aluminum |
|---|---|---|
| Equipment ground (bare / green) (Table 250.122) | 12 AWG | 10 AWG |
The equipment ground is sized by the breaker, not the load: a 20A breaker falls in Table 250.122's 20 A row. Upsize the hots for voltage drop and the ground must grow in proportion (NEC 250.122(B)). Every size, with a worked upsizing example, is in the ground wire size chart.
How far can you run it? (voltage drop)
Keeping voltage drop under the recommended 3% at a 16 A load (80% of the breaker), 12 AWG copper is good for roughly:
| System voltage | Max one-way run (12 AWG Cu) |
|---|---|
| 120 V | ≈ 56 ft |
| 240 V | ≈ 113 ft |
Past these distances, step up one gauge. Run your exact length and load through the voltage drop calculator.
What runs on 20 amps
- Kitchen small-appliance circuits
- Bathroom & garage outlets
- Laundry receptacle
Common receptacle at this rating: NEMA 5-20.
Parts for a 20 A circuit
A 20 A circuit takes 5-20 receptacles. Commercial-grade devices keep their contact grip for decades where builder-grade ones loosen and heat, and kitchens, bathrooms, garages and outdoor outlets need GFCI protection.
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20 A receptacle
Leviton TBR20 Commercial-Spec 20A Duplex
Best for: Kitchen, garage and workshop 20 A circuits
Non-contact voltage tester
Klein Tools NCVT-3P
Best for: Confirming a circuit is dead before you open a device or box
Frequently asked questions
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