220V Wire Size
Calculate the correct wire gauge (AWG) for 220V circuits using voltage drop formulas. Free online electrical wire sizing calculator for single-phase and three-phase systems.
About This Calculator
The 220V Wire Size Calculator helps electricians, DIY enthusiasts, and engineers determine the correct wire gauge for 220V electrical circuits. Selecting the right wire size is critical for safety, efficiency, and code compliance. An undersized wire can overheat and cause fires, while an oversized wire wastes money on unnecessary copper.
The calculator uses the NEC-recommended voltage drop method based on Ohm's law and Pouillet's law. The cross-sectional area is calculated as A = I × ρ × φ × L / V_drop, where φ = 2 for single-phase and φ = √3 for three-phase systems. Temperature correction adjusts the conductor resistivity using its temperature coefficient. The result is then rounded up to the nearest standard AWG size for safety.
Regional Notes
International (220-240V): Most countries outside North America use 220-240V at 50 Hz. Common household circuits include 10A lighting, 16A outlets, and 32A cookers. Wire sizes are typically specified in mm² rather than AWG. The calculator provides AWG output but can be cross-referenced to mm².
North America (240V split-phase): The US and Canada use 120/240V split-phase systems. 240V circuits are used for large appliances like dryers, ranges, and HVAC equipment. Common wire sizes include 10 AWG for 30A, 8 AWG for 40A, and 6 AWG for 50A circuits per NEC guidelines.
UK (230V): The UK uses 230V single-phase for domestic installations. BS 7671 (IET Wiring Regulations) specifies cable sizes in mm². A 2.5 mm² cable is standard for 16A radial circuits, while 4 mm² and 6 mm² cables are used for 32A and 40A ring circuits respectively.
Important: Always consult a qualified electrician and follow local electrical codes before installing any wiring. This calculator provides estimates for informational purposes only.
Frequently Asked Questions
What wire size do I need for a 220V circuit?
The wire size depends on the current draw, distance, conductor material, and allowable voltage drop. For a typical 20A 220V circuit running 30 meters with copper wire and 3% allowable drop, 14 AWG is sufficient. Use the calculator above to get the precise size for your specific installation.
How is wire size calculated for 220V?
Wire size is calculated using Ohm's law and Pouillet's law: A = I × ρ × 2L / V_drop, where A is cross-sectional area, I is current, ρ is resistivity, L is one-way distance, and V_drop is the allowable voltage drop. For three-phase systems, the factor 2 is replaced by √3.
What is the difference between single-phase and three-phase wire sizing?
In single-phase systems, current flows through two conductors (live and neutral), so the total wire length is twice the one-way distance. In three-phase systems, three conductors share the load, and the effective length factor is √3 instead of 2. Three-phase systems can carry more power with smaller wire sizes.
Does temperature affect wire size selection?
Yes, conductor resistivity increases with temperature. Copper has a temperature coefficient of 0.00404 per °C, meaning its resistivity increases by about 0.4% for every °C above the reference temperature of 20°C. Always use the expected maximum operating temperature for accurate wire sizing.
What is the standard voltage drop limit for 220V circuits?
The National Electrical Code (NEC) recommends a maximum voltage drop of 3% at the farthest outlet for branch circuits and 5% total from the service panel to the final load. For a 220V circuit, 3% equals 6.6V and 5% equals 11V.
Can I use aluminum wire for 220V circuits?
Yes, aluminum wire can be used for 220V circuits, but it requires a larger gauge than copper for the same current because aluminum has higher resistivity (2.65×10⁻⁸ Ω·m vs 1.68×10⁻⁸ Ω·m for copper). Aluminum is commonly used for large feeders and service entrances.
What AWG is 220V wire in Europe vs North America?
Europe uses 230V (previously 220V) and typically uses metric wire sizes in mm² rather than AWG. A 2.5 mm² wire (roughly 14 AWG) is standard for 16A lighting and outlet circuits. North America uses 120/240V split-phase and typically uses 12 AWG for 20A circuits and 10 AWG for 30A circuits.
How do I convert wire size from mm² to AWG?
To convert mm² to AWG, calculate the diameter from area using d = √(4A/π), then use the formula AWG = 36 − 39 × log₉₂(d/0.127). The calculator above handles this conversion automatically and recommends the next standard AWG size up for safety.