Recommended Gauge
10 AWG
Voltage Drop
2.07%
Actual Voltage
117.5V
Power Loss
50W
Check equipment nameplate or breaker rating
Distance from panel to load (not round trip)
NEC recommends 3% max for branch circuits
Recommended Gauge
10 AWG
5.26 mm²
Voltage Drop
2.07%
2.48V
Voltage at Load
117.5V
of 120V
Power Loss
50W
I × VD
| AWG | mm² | Cu Amps | Al Amps |
|---|---|---|---|
| 14 | 2.08 | 15A | - |
| 12 | 3.31 | 20A | 15A |
| 10 | 5.26 | 30A | 25A |
| 8 | 8.37 | 40A | 35A |
| 6 | 13.3 | 55A | 45A |
| 4 | 21.2 | 70A | 60A |
| 3 | 26.7 | 85A | 70A |
| 2 | 33.6 | 95A | 85A |
| 1 | 42.4 | 110A | 95A |
| 1/0 | 53.5 | 125A | 110A |
Ampacity based on NEC Table 310.16 (75°C rating)
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Price as of Oct 14, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Inputs
Result
12 AWG has 1.98 ohms/1000ft resistance. VD = (2 × 50 × 1.98 × 20) / 1000 = 3.96V = 3.3% -- exceeds 3% limit. 10 AWG has 1.24 ohms/1000ft. VD = (2 × 50 × 1.24 × 20) / 1000 = 2.48V = 2.07% -- acceptable. Recommended: 10 AWG.
Inputs
Result
8 AWG aluminum: resistance = 0.778 × 1.6 = 1.245 ohms/1000ft. VD = (2 × 100 × 1.245 × 30) / 1000 = 7.47V = 3.11% -- exceeds 3%. 6 AWG aluminum: resistance = 0.491 × 1.6 = 0.786 ohms/1000ft. VD = (2 × 100 × 0.786 × 30) / 1000 = 4.71V = 1.96% -- acceptable.
Wire gauge depends on amperage (current draw), distance, and acceptable voltage drop. Higher amperage needs thicker wire (lower AWG number). Longer distances need thicker wire to prevent excessive voltage drop.
| Circuit Amps | Min Copper AWG | Max Distance (3% drop, 120V) | Common Use |
|---|---|---|---|
| 15A | 14 AWG | 50 ft | Lighting, receptacles |
| 20A | 12 AWG | 40 ft | Kitchen, bathroom |
| 30A | 10 AWG | 30 ft | Dryer, water heater |
| 40A | 8 AWG | 25 ft | Range, cooktop |
| 50A | 6 AWG | 20 ft | Subpanel, EV charger |
Voltage drop is the loss of electrical pressure as current travels through wire. Excessive drop (>3% for branch circuits, >5% total) causes equipment malfunction, dimming lights, and wasted energy. Longer runs need thicker wire.
For a 20-amp circuit, use 12 AWG wire for runs up to 50 feet. For longer distances, consider 10 AWG to minimize voltage drop. Always follow local electrical codes.
AWG (American Wire Gauge) is used in North America - lower numbers mean thicker wire. mm² is the metric standard measuring cross-sectional area. For example: 14 AWG ≈ 2.08 mm², 12 AWG ≈ 3.31 mm².
| AWG | mm² | Diameter (mm) | Ampacity (Copper, 60°C) |
|---|---|---|---|
| 14 AWG | 2.08 mm² | 1.63 mm | 15A |
| 12 AWG | 3.31 mm² | 2.05 mm | 20A |
| 10 AWG | 5.26 mm² | 2.59 mm | 30A |
| 8 AWG | 8.37 mm² | 3.26 mm | 40A |
| 6 AWG | 13.30 mm² | 4.11 mm | 55A |
| 4 AWG | 21.15 mm² | 5.19 mm | 70A |
Copper is more conductive, smaller, and easier to work with. Aluminum is cheaper but requires larger gauges for the same ampacity. Aluminum also needs special connectors and is typically used only for service entrances and feeders.
| Property | Copper | Aluminum |
|---|---|---|
| Conductivity | 100% IACS | 61% IACS |
| Size for 100A | 3 AWG | 1 AWG |
| Cost (per ft, 100A) | $4–$7 | $2–$4 |
| Weight (per ft) | Heavier | 70% lighter |
| Typical Use | Branch circuits | Service entrance, feeders |
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Last Updated: Oct 14, 2026
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