Wire Size Calculator
Avoid electrical fires and voltage drop issues. Calculate the exact American Wire Gauge (AWG) needed for your project across any distance.
Last updated: February 24, 2026
Pulling wires through conduit? Check legal fill limits
Distance measured from breaker to load.
Recommended Minimum Size
Voltage Drop
2.07%
2.49 Volts Lost
Wire Capacity
35 Amps
At 75°C Insulation (NEC)
The Two Rules of Sizing Wire
The absolute most important rule is safety. If you push 50 amps through a tiny wire rated for only 15 amps, the wire will glow red hot like a toaster coil and instantly start a fire. The National Electrical Code strictly dictates the absolute minimum thickness a wire must be to safely carry a specific amperage without melting its insulation.
The secondary rule is efficiency. Running 20 amps through a 12 AWG wire is perfectly safe regarding heat. However, if you run that 12 AWG wire 300 feet to a detached garage, the inherent resistance of the copper acts like friction, restricting the voltage. At the end of that 300 foot run, you won't have 120 volts anymore. To fix this, you must "upsize" the wire to 8 AWG just to reduce the friction.
Frequently Asked Questions
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