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Wire Size Calculator

Wire Size Calculator

Calculate minimum wire gauge (AWG) based on voltage drop requirements

Electrical Wire Sizing
Enter circuit parameters to find minimum wire size

NEC recommends 3% for branch circuits

Voltage Drop Theory

Ohm's Law Application:

V=I×RV = I \times R

Voltage drop occurs due to wire resistance

Wire Resistance Formula:

R=K×LCMR = \frac{K \times L}{CM}
  • • K = resistivity (12.9 for copper at 75°C)
  • • L = one-way distance in feet
  • • CM = circular mil area

Phase Multipliers:

  • • Single-phase: 2 (accounts for return path)
  • • Three-phase: 1.732 (√3 factor)
NEC Code Requirements

Voltage Drop Limits

  • • Branch circuits: 3% maximum
  • • Feeders: 3% maximum
  • • Total system: 5% maximum
  • • Critical loads: 2% recommended

Wire Selection Criteria

  • • Ampacity must exceed circuit current
  • • Voltage drop within acceptable limits
  • • Appropriate insulation rating
  • • Environmental considerations

Installation Factors

  • • Ambient temperature derating
  • • Conduit fill considerations
  • • Proper termination methods
  • • Code compliance verification
AWG Wire Size Reference
AWGCircular MilsDiameter (in)Ampacity (A)Weight (lbs/1000ft)
144,1100.0642012.43
126,5300.0812519.77
1010,3800.1023531.43
816,5100.1285050.97
626,2400.1626579.46
441,7400.20485125.1
266,3600.258115197.4
183,6900.289130248.1
1/0105,6000.325150312.1
2/0133,1000.365175392.8
3/0167,8000.410200494.1
4/0211,6000.460230621.9

* Ampacities based on 75°C conductor rating in raceway