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Voltage Drop Calculator

Voltage drop describes how the supplied energy of a voltage source is reduced as electric current moves through an electrical circuit. The voltage drop calculator will help determine proper wire size for a cable run based on voltage drop and current carrying capacity.

1. Initial Voltage

2. AC / DC

3. Current (Amps)

4. Cable Length (ft)

5. Cable Gauge (AWG)



Note: Industry standard is a voltage drop of no greater than 10%.

How to use this tool:

  1. Enter the initial voltage. Choose if your system operates on 12 V or 24 V
  2. Select AC or DC. Choose which voltage type your system operates. Typically the overall selections will be 12 Vdc and 24 Vac
  3. Enter the current of your camera in amps. Note: 1 amp = 1000 mA. Thus, if your camera draws 300 mA, enter 0.3 into this field
  4. Enter the distance of your cable in feet
  5. Enter the size of your cable. CCTV standard is 18 awg
  6. Click 'Calculate.' Click 'Cancel' to clear the results and start again.

Example 1

At 12 Vdc, a 300 mA camera at 100 feet on standard 18 awg will have a voltage drop of 0.38 volts. Industry standard is +/- 10% which is 1.2 volts. In this example, you are within limits.

Example 2

12 Vdc, 0.8 amps or 800 ma (not unreasonable for an IR camera) at a distance of 150 feet on 18 awg would give you a drop of 1.54 volts, which is greater than acceptable limits. The way to get around this is to have a shorter cable run, or increase the size of your power wire. In this example, increasing the power wire to 16 awg would decrease the voltage drop to 0.96 volts, which is within limits.