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Voltage Drop Calculator

Pick the voltage, the load, the one way length and the wire size. The calculator shows the voltage drop in volts and percent, and names the wire size that fixes a long run.

Wire size, length and load in, percent drop out.

  • Copper and aluminum, sizes 14 AWG through 1/0
  • Checks the result against the 3 percent guide in the National Electrical Code
  • Names the smallest listed wire that passes

How It Works

For a single phase circuit, drop equals 2 times K times amps times feet, divided by the wire's circular mils. K is 12.9 for copper and 21.2 for aluminum. Circular mil areas come from Chapter 9 Table 8 of the National Electrical Code.

How A Business Would Use It

An electrician can put this on a page about shop wiring, well pumps or car chargers. People planning a long run find it, and the note under the answer tells them when to call.

Who it fits. Electricians, solar installers and electrical supply houses.

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Where To Find The Studio

235 E Broadway #800, Long Beach, CA 90802