Voltage Drop Calculator
What is Voltage Drop?
Voltage drop is the reduction in electrical potential along the path of a current flowing in an electrical circuit. Voltage drops across internal resistances of the source, across conductors, across contacts, and across connectors are undesirable because some of the energy supplied is dissipated (lost).
Why Calculate Voltage Drop?
Calculating voltage drop is essential for proper electrical system design. Excessive voltage drop can cause:
- Dimming of lights and poor performance of appliances
- Overheating of equipment, which can lead to premature failure
- Increased energy consumption and higher electricity bills
- Potential safety hazards in critical systems
Voltage Drop Formula
The basic formula for calculating voltage drop in a DC circuit is:
Vdrop = 2 × L × I × R / 1000
Where:
- Vdrop = Voltage drop (V)
- L = Length of the wire (one way) in feet
- I = Current in amperes (A)
- R = Wire resistance in ohms per 1000 feet (Ω/1000ft)
For AC single-phase circuits, the formula is similar but may include a power factor:
Vdrop = 2 × L × I × R × PF / 1000
For AC three-phase circuits, the formula is:
Vdrop = √3 × L × I × R × PF / 1000
Acceptable Voltage Drop
According to the National Electrical Code (NEC), the maximum recommended voltage drop is:
- 3% for branch circuits
- 5% for the combined feeder and branch circuit
How to Use the Voltage Drop Calculator
- Select the circuit type (DC, AC Single Phase, or AC Three Phase)
- Enter the wire length (one-way distance)
- Enter the current (in amperes)
- Select the wire size (AWG or mm²)
- Choose the conductor material (copper or aluminum)
- Enter the system voltage
- Click "Calculate" to see the results
Tips for Reducing Voltage Drop
- Use larger wire sizes (lower AWG numbers)
- Reduce the length of the circuit when possible
- Use copper conductors instead of aluminum when feasible
- Increase the system voltage (where applicable)
- Distribute loads more evenly across multiple circuits