Find the correct cable size for your load – Copper or Aluminum
Note: Based on NEC 2023 Table 310.16 (75°C column commonly used)
Max Ampacity: -- A
Safe – wire can handle the load
Our professional Wire Size Calculator helps electricians, engineers, DIY enthusiasts, and homeowners determine the correct wire gauge for electrical installations. Whether you're planning home wiring projects, designing electrical circuits, installing appliances, or ensuring electrical code compliance, this tool provides accurate wire sizing based on current, voltage, distance, and insulation type.
Calculate wire gauge requirements, determine ampacity ratings, check voltage drop limits, select proper insulation types, and ensure electrical safety compliance with our specialized electrical engineering calculator that follows NEC (National Electrical Code) standards and international wiring regulations.
Based on NEC Article 310 and Table 310.15(B)(16) for ampacity. Includes derating factors for ambient temperature, conduit fill, and continuous loads. Essential for passing electrical inspections.
Calculates voltage drop using NEC-recommended 3% for branch circuits, 5% for feeders. Ensures appliances receive proper voltage and prevents equipment damage from undervoltage.
Prevents overheating and electrical fires by ensuring wires are properly sized for their current load. Includes safety margins and considers worst-case scenarios for maximum protection.
Compares copper vs aluminum wiring costs and specifications. Helps choose between AWG (American Wire Gauge) and metric (mm²) sizes for international projects.
Used by licensed electricians, electrical engineers, contractors, and DIY homeowners worldwide. Prevent electrical hazards and ensure code compliance with accurate wire sizing!
For a 20-amp circuit, you need 12 AWG copper wire for most applications. However, for longer runs (over 50 feet), you may need 10 AWG to prevent excessive voltage drop. Always check local codes and consider derating factors for conduit fill and ambient temperature.
AWG (American Wire Gauge) is used in North America (smaller number = larger wire). mm² (square millimeters) is used internationally. Conversion: 14 AWG = 2.08 mm², 12 AWG = 3.31 mm², 10 AWG = 5.26 mm². Our calculator handles both systems.
Voltage drop increases with wire length and current. NEC recommends maximum 3% drop for branch circuits, 5% for feeders. Example: 100-foot 12 AWG wire with 15 amps drops about 3.8 volts at 120V (3.2%). Our calculator ensures you stay within limits.
Aluminum wire is cheaper and lighter but requires one size larger than copper for same ampacity. Use aluminum for: service entrance cables, large feeders, overhead lines. Never use for 15-20A branch circuits without special connectors rated for aluminum.
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