Voltage Drop Calculator

Low voltage lighting allows for small fixtures, efficient lamping, and safe installation and adjustment. The Voltage Drop Calculator will determine the correct THHN wire sizes for recommended 3% or less drop in voltage for each circuit based on the specified wattage. Lengths are the distance from the remote magnetic transformer to that system power feed connector, or power supply.

Voltage
Wattage
Size of Copper Gauge Wire
Tap
Range (In Feet)

Examples

  • Assume 12volt AC at 300 watts calculating maximum conductor size.
  • Phase: Single
  • Conductor: Copper
  • Installation: Conduit
  • Voltage: 12VAC
  • Voltage drop: 3%
  • Length of the cable run: 30ft
  • Current: 25amp (300/12)
  • It will suggest to use #3.
  • Assume 12volt AC at 300 watts calculating maximum length allowed with a specific wire size.
  • Phase: Single
  • Conductor: Copper
  • Installation: Conduit
  • Conductor Size: 8
  • Voltage: 12VAC
  • Voltage drop: 3%
  • Current: 25amp (300/12)
  • It will suggest to go maximum 10.5 ft.