Wire Size by Amperage
The amperage of your circuit is one of the two primary factors that determine wire size (the other being distance). Higher amperage requires larger conductors to safely carry the current without overheating and to keep voltage drop within acceptable limits. This section provides complete wire sizing tables organized by circuit amperage, covering every standard breaker size from 15 amps to 200 amps. Each page shows the recommended wire gauge for both copper and aluminum at every common run distance.
Select Your Circuit Amperage
15 Amp
Min copper: 14 AWG
Bedroom receptacles, living room lighting, hallway circuits
View Wire Sizes →20 Amp
Min copper: 14 AWG
Kitchen countertop outlets, bathroom GFCI, laundry receptacles
View Wire Sizes →30 Amp
Min copper: 10 AWG
Electric dryers, window AC units, well pumps
View Wire Sizes →40 Amp
Min copper: 8 AWG
Mid-size electric ranges, large AC condensers, heat pump systems
View Wire Sizes →50 Amp
Min copper: 8 AWG
Full-size electric ranges, EV chargers (Level 2), hot tubs and spas
View Wire Sizes →60 Amp
Min copper: 6 AWG
Small subpanels, premium EV chargers (48A continuous), tankless water heater circuits
View Wire Sizes →80 Amp
Min copper: 4 AWG
Mid-size subpanels, workshop feeders, home addition feeders
View Wire Sizes →100 Amp
Min copper: 3 AWG
Detached garage subpanels, workshop feeders, small service entrances
View Wire Sizes →125 Amp
Min copper: 1 AWG
Large subpanels, in-law suite feeders, commercial tenant feeds
View Wire Sizes →150 Amp
Min copper: 1/0 AWG
Large detached structure feeders, commercial sub-distribution, mid-size service entrances
View Wire Sizes →200 Amp
Min copper: 3/0 AWG
Residential main service entrance, large detached structure feeders, commercial branch service
View Wire Sizes →Quick Reference: Minimum Wire Size by Amperage
The table below shows the NEC minimum wire gauge for each standard amperage based on NEC Table 310.16 ampacity ratings at 75 degrees C. These minimums apply when voltage drop is not a concern (short runs of 25 feet or less). For longer runs, the required wire gauge will be larger. Click any amperage above for complete distance-based sizing tables.
| Amperage | Min Copper (75°C) | Min Aluminum (75°C) | Common Uses |
|---|---|---|---|
| 15A | 14 AWG | 14 AWG | Bedroom receptacles, living room lighting |
| 20A | 14 AWG | 12 AWG | Kitchen countertop outlets, bathroom GFCI |
| 30A | 10 AWG | 8 AWG | Electric dryers, window AC units |
| 40A | 8 AWG | 8 AWG | Mid-size electric ranges, large AC condensers |
| 50A | 8 AWG | 6 AWG | Full-size electric ranges, EV chargers (Level 2) |
| 60A | 6 AWG | 4 AWG | Small subpanels, premium EV chargers (48A continuous) |
| 80A | 4 AWG | 3 AWG | Mid-size subpanels, workshop feeders |
| 100A | 3 AWG | 1 AWG | Detached garage subpanels, workshop feeders |
| 125A | 1 AWG | 2/0 AWG | Large subpanels, in-law suite feeders |
| 150A | 1/0 AWG | 3/0 AWG | Large detached structure feeders, commercial sub-distribution |
| 200A | 3/0 AWG | 250 kcmil | Residential main service entrance, large detached structure feeders |
Understanding Amperage and Wire Sizing
The amperage rating of a circuit determines the minimum conductor size needed for safe operation. The NEC establishes ampacity ratings for each wire gauge in Table 310.16, which specifies the maximum continuous current a conductor can carry without exceeding its temperature rating. Using a wire gauge that is too small for the amperage creates a fire hazard, as the excessive current causes the conductor to overheat and can degrade or melt the insulation.
The circuit breaker provides a critical safety backup by interrupting the circuit if the current exceeds the wire's rated ampacity. The breaker must be sized to match the conductor's ampacity, not the load. For example, a circuit with 12 AWG wire must use a 20-amp breaker (matching the 20-amp ampacity of 12 AWG at 60 degrees C). Using a 30-amp breaker with 12 AWG wire would be a code violation and a safety hazard, because the wire could overheat before the breaker trips.
For continuous loads, the NEC requires sizing conductors at 125% of the continuous load current. A 16-amp continuous load requires conductors rated for 20 amps (16 x 1.25 = 20). The 125% factor provides additional thermal margin for sustained operation. Non-continuous loads (those that cycle on and off or operate intermittently) do not require this derating.
Beyond ampacity, voltage drop must also be considered. At higher amperages, the voltage drop for any given wire gauge increases proportionally. This means that high-amperage circuits are more sensitive to distance and require more aggressive upsizing for longer runs. The individual amperage pages in this section provide complete distance tables showing exactly where the gauge needs to increase to maintain acceptable voltage drop.