AWG Wire Size Chart
Electrical wire gauge reference for HVAC installations
AWG Wire Specifications & Ampacity
Copper conductor ampacity ratings per NEC Table 310.16. Based on 30°C (86°F) ambient temperature.
| AWG | Diameter (mm) | Area (mm²) | Resistance (Ω/km) | 60°C (TW) | 75°C (THW) | 90°C (THWN-2) | Typical HVAC Use |
|---|---|---|---|---|---|---|---|
| 18 | 1.02 | 0.82 | 21.0 | - | - | 14A | Thermostat wire |
| 16 | 1.29 | 1.31 | 13.2 | - | - | 18A | Control circuits |
| 14 | 1.63 | 2.08 | 8.28 | 15A | 20A | 25A | 15A circuits, small AC |
| 12 | 2.05 | 3.31 | 5.21 | 20A | 25A | 30A | 20A circuits, 1-1.5 ton AC |
| 10 | 2.59 | 5.26 | 3.28 | 30A | 35A | 40A | 2-3 ton AC, heat pumps |
| 8 | 3.26 | 8.37 | 2.06 | 40A | 50A | 55A | 3-5 ton AC, large heat pumps |
| 6 | 4.11 | 13.30 | 1.30 | 55A | 65A | 75A | 5-7 ton AC, commercial |
| 4 | 5.19 | 21.15 | 0.815 | 70A | 85A | 95A | Large commercial |
| 3 | 5.83 | 26.67 | 0.646 | 85A | 100A | 115A | Service entrance |
| 2 | 6.54 | 33.62 | 0.513 | 95A | 115A | 130A | Service entrance |
| 1 | 7.35 | 42.41 | 0.406 | 110A | 130A | 145A | Main service |
| 1/0 | 8.25 | 53.49 | 0.322 | 125A | 150A | 170A | Main service |
| 2/0 | 9.27 | 67.43 | 0.256 | 145A | 175A | 195A | Main service |
| 3/0 | 10.40 | 85.03 | 0.203 | 165A | 200A | 225A | 200A service |
| 4/0 | 11.68 | 107.2 | 0.161 | 195A | 230A | 260A | 200A+ service |
* Ampacity based on NEC Table 310.16 for copper conductors in raceway/cable. Derate for ambient temperature >30°C, bundled conductors, or continuous loads.
AWG to mm² Quick Reference
| AWG | mm² | Common Metric |
|---|---|---|
| 18 | 0.82 | 0.75 mm² |
| 16 | 1.31 | 1.5 mm² |
| 14 | 2.08 | 2.5 mm² |
| 12 | 3.31 | 4 mm² |
| 10 | 5.26 | 6 mm² |
| 8 | 8.37 | 10 mm² |
| 6 | 13.3 | 16 mm² |
| 4 | 21.2 | 25 mm² |
| 2 | 33.6 | 35 mm² |
| 1/0 | 53.5 | 50 mm² |
Insulation Temperature Ratings
60°C (140°F)
TW, UF - Basic insulation. Indoor use, dry locations.
75°C (167°F)
THW, THWN, XHHW - Most common. Wet/dry locations.
90°C (194°F)
THWN-2, XHHW-2, THHN - High temp. Conduit/raceway.
Note: NEC requires using the 75°C column for most terminations, even with 90°C wire.
Voltage Drop Reference
Maximum recommended voltage drop: 3% for branch circuits, 5% total (feeder + branch).
| AWG | Maximum One-Way Distance (feet) for 3% Drop | |||
|---|---|---|---|---|
| 15A @ 120V | 20A @ 120V | 30A @ 240V | 50A @ 240V | |
| 14 | 50 ft | 38 ft | 50 ft | - |
| 12 | 79 ft | 59 ft | 79 ft | 48 ft |
| 10 | 125 ft | 94 ft | 125 ft | 75 ft |
| 8 | 199 ft | 149 ft | 199 ft | 119 ft |
| 6 | 316 ft | 237 ft | 316 ft | 189 ft |
Voltage Drop Formula: VD = (2 × L × I × R) / 1000
Where: L = one-way length (ft), I = current (A), R = resistance (Ω/1000ft)
Percentage: VD% = (VD / V) × 100
HVAC Equipment Wiring Quick Guide
| Equipment | Typical Load | Min. Wire | Breaker | Notes |
|---|---|---|---|---|
| 1 Ton Split AC (240V) | 5-7A | 14 AWG | 15A | Check nameplate |
| 2 Ton Split AC (240V) | 8-12A | 12 AWG | 20A | Most common residential |
| 3 Ton Split AC (240V) | 12-18A | 10 AWG | 25-30A | Verify MCA/MOP |
| 5 Ton Split AC (240V) | 18-25A | 8 AWG | 35-40A | Verify MCA/MOP |
| Electric Furnace (10kW) | 42A | 8 AWG | 50A | May need 6 AWG |
| Heat Pump (3 Ton) | 15-20A | 10 AWG | 30A | Aux heat separate |
Important: Always use equipment nameplate MCA (Minimum Circuit Ampacity) for wire sizing and MOP (Maximum Overcurrent Protection) for breaker sizing. These values take into account starting current and other factors.