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⚡ Wire Gauge Reference

Electrical wire gauge sizes, ampacity ratings, and common applications for construction.

Understanding Wire Gauge​

AWG = American Wire Gauge

Lower number = thicker wire = more current capacity

Common Wire Gauges​

AWGDiameter (inches)Ampacity*Common Use
140.064115ALighting circuits, outlets
120.080820AOutlets, small appliances
100.101930AWater heaters, dryers
80.128540ALarge appliances, subpanels
60.162055AElectric ranges, subpanels
40.204370AService entrance, feeders
20.257695AService entrance, large feeders
1/00.3249125AService entrance
2/00.3648145AService entrance
3/00.4096165AService entrance
4/00.4600195AService entrance

*60°C copper wire, single conductor in free air (NEC Table 310.15(B)(16))

Residential Applications​

15-Amp Circuits (14 AWG)​

  • Use: General lighting, outlets
  • Breaker: 15A
  • Wire: 14 AWG
  • Max Load: 1,440W (80% of 15A × 120V)

20-Amp Circuits (12 AWG)​

  • Use: Kitchen outlets, bathroom outlets, small appliances
  • Breaker: 20A
  • Wire: 12 AWG
  • Max Load: 1,920W (80% of 20A × 120V)

30-Amp Circuits (10 AWG)​

  • Use: Water heaters, dryers (if 30A)
  • Breaker: 30A
  • Wire: 10 AWG
  • Max Load: 5,760W (30A × 240V)

40-Amp Circuits (8 AWG)​

  • Use: Large water heaters, some dryers
  • Breaker: 40A
  • Wire: 8 AWG
  • Max Load: 7,680W (40A × 240V)

50-Amp Circuits (6 AWG)​

  • Use: Electric ranges, large appliances
  • Breaker: 50A
  • Wire: 6 AWG
  • Max Load: 9,600W (50A × 240V)

Commercial Applications​

100-Amp Service (2 AWG)​

  • Use: Small commercial buildings
  • Wire: 2 AWG (or 1 AWG)
  • Voltage: 120/240V single-phase

200-Amp Service (2/0 AWG)​

  • Use: Standard commercial, larger residential
  • Wire: 2/0 AWG (or 3/0 AWG)
  • Voltage: 120/240V single-phase or 208Y/120V three-phase

400-Amp Service (500 kcmil)​

  • Use: Large commercial buildings
  • Wire: 500 kcmil (or parallel runs)
  • Voltage: 208Y/120V or 480Y/277V three-phase

Wire Types​

THHN/THWN​

  • Use: Most common building wire
  • Rating: 90°C (THHN), 75°C (THWN)
  • Location: Dry (THHN) or wet (THWN)

UF (Underground Feeder)​

  • Use: Direct burial, outdoor
  • Rating: 60°C
  • Location: Underground, wet locations

MC (Metal Clad)​

  • Use: Commercial, exposed runs
  • Rating: 90°C
  • Location: Exposed, concealed

SER (Service Entrance)​

  • Use: Service entrance, feeders
  • Rating: 75°C
  • Location: Service panels

Color Coding​

Standard Colors (120/240V)​

ColorUse
BlackHot (Line 1)
RedHot (Line 2)
WhiteNeutral
Green/BareGround

Three-Phase (208Y/120V or 480Y/277V)​

ColorUse
BlackPhase A
RedPhase B
BluePhase C
WhiteNeutral
Green/BareGround

Ampacity Derating​

Wire ampacity must be derated for:

Temperature​

Ambient TempDerating Factor
86-95°F0.91
96-104°F0.82
105-113°F0.71

Multiple Conductors​

Conductors in RacewayDerating Factor
4-60.80
7-90.70
10-200.50
21-300.45

Voltage Drop​

Long runs may require larger wire to prevent voltage drop:

DistanceVoltage Drop (3%)Wire Size Increase
< 100 ftUsually OKNone
100-200 ftMay need +1 size12→10 AWG
200-300 ftMay need +2 sizes12→8 AWG
> 300 ftCalculateUse voltage drop calculator

Common Mistakes​

MistakeProblemSolution
Using 14 AWG on 20A circuitFire hazardUse 12 AWG minimum
Not derating for temperatureOverheatingApply derating factors
Ignoring voltage dropPoor performanceSize up for long runs
Wrong wire type for locationCode violationUse appropriate type
Undersized serviceOverloadSize for actual load

Quick Reference​

Residential​

  • Lighting/outlets: 14 AWG (15A) or 12 AWG (20A)
  • Water heater: 10 AWG (30A) or 8 AWG (40A)
  • Electric range: 6 AWG (50A)
  • Service: 2/0 AWG (200A)

Commercial​

  • General circuits: 12 AWG (20A)
  • Receptacles: 12 AWG (20A)
  • Lighting: 12 AWG (20A)
  • Service: 2/0 AWG (200A) or larger

NEC Code References​

  • Table 310.15(B)(16): Ampacity ratings
  • Article 210: Branch circuits
  • Article 220: Load calculations
  • Article 310: Conductors
Always Follow Code

Wire sizing must comply with NEC (National Electrical Code). When in doubt, consult a licensed electrician or electrical engineer.