Automatically recommends the correct AWG wire gauge based on current, voltage, and distance. Validates both ampacity and voltage drop to ensure safe wire selection. Built-in NEC ampacity data for copper and aluminum conductors.
✓ NEC Standard · ✓ Copper/Aluminum · ✓ Single/Three-Phase⚙️ Input Parameters
📋 AWG Ampacity Reference Table (NEC Table 310.16)
Based on NEC standard, 75°C temperature rating. After calculating, the recommended gauge row will be highlighted.
| AWG | Diameter (mm) | Area (mm²) | Copper Ampacity (A) | Aluminum Ampacity (A) | Resistance (Ω/km) |
|---|
About Wire Size Calculation
Choosing the correct wire size is critical for electrical safety. Undersized wires can overheat, cause excessive voltage drop, and even start fires. This calculator is based on the following principles:
- Ampacity check: The wire must safely carry the operating current without overheating
- Voltage drop check: Voltage loss over long distances must stay within acceptable limits
- Take the larger: Of the two AWG values calculated, use the thicker wire (smaller AWG number)
Voltage drop formula: Single-phase VD = 2 × L × I × ρ / A; Three-phase VD = √3 × L × I × ρ / A. Where L is one-way length, I is current, ρ is resistivity, and A is cross-sectional area.
Frequently Asked Questions
How do I choose the correct wire size?
Choosing the correct wire size requires meeting two conditions simultaneously: 1) Ampacity — the wire's rated current-carrying capacity must be greater than or equal to the actual operating current; 2) Voltage drop — NEC recommends branch circuit voltage drop not exceeding 3%, feeders not exceeding 2%, and total not exceeding 5%. This calculator validates both conditions and recommends the smallest AWG that satisfies both.
What does AWG mean? Does a higher number mean a thicker wire?
AWG (American Wire Gauge) is the standard wire gauge system used in North America. Counterintuitively, a higher AWG number means a thinner wire. For example, AWG 14 has a diameter of about 1.63mm, while AWG 4 has a diameter of about 5.19mm. Common household wiring ranges from AWG 14 (lighting) to AWG 2/0 (large feeders).
What's the difference between copper and aluminum wire?
Copper wire has higher conductivity (resistivity 0.0175 Ω·mm²/m) and greater ampacity, but is more expensive. Aluminum wire has higher resistivity (0.0282 Ω·mm²/m) and requires a larger cross-section to achieve the same ampacity, but is cheaper and lighter. Copper is recommended for residential wiring, while aluminum is often used for long-distance overhead lines.
How much voltage drop is acceptable?
The NEC recommends: feeder circuit voltage drop not exceeding 2%, branch circuits not exceeding 3%, and the total not exceeding 5%. In practice, less than 3% is ideal, 3-5% is acceptable, and above 5% requires increasing the wire gauge.