Voltage Drop Calculator

Voltage Drop Calculator

How to Use the Voltage Drop Calculator

A Voltage Drop Calculator is a tool used to determine the amount of voltage lost as electrical current travels through a wire due to resistance, ensuring proper wire sizing and circuit performance.

Why Voltage Drop Matters

When electricity travels through a conductor (like copper or aluminum wires), some energy is lost due to resistance. This voltage drop can affect the performance of electrical equipment—especially over long distances or with high current.

How to Use the Calculator

Step 1: Enter the Current

  • Input the current in amperes (A) your circuit will carry.
  • Example: 20 A for a small motor.

Step 2: Enter the Cable Length

  • Enter the one-way length of the cable in meters.
  • For example, if the cable runs 30 meters to a device, enter 30.

Step 3: Enter the Resistance per Meter

  • Input the resistance of the wire in ohms per meter (Ω/m).
  • You can get this from the wire’s specs:
    • Copper: ~0.017 Ω/m
    • Aluminum: ~0.028 Ω/m

Step 4: Select the Number of Conductors

  • Choose the type of circuit:
    • DC or single wire return = 1 conductor
    • Single Phase AC = 2 wires
    • Three Phase = 3 wires

Step 5: Click “Calculate”

  • The calculator will output:
    • Total Voltage Drop in volts (V)
    • Percentage Voltage Drop relative to 230V (assumed)

Example Calculation

  • Current: 20 A
  • Length: 30 m
  • Resistance: 0.017 Ω/m (Copper)
  • Circuit: Single Phase (2 wires)

Voltage Drop = 20 × 0.017 × 30 × 2 = 20.4 V
% Drop = (20.4 ÷ 230) × 100 ≈ 8.87%

Guidelines

  • For general wiring, the voltage drop should not exceed 5%.
  • Always refer to local electrical codes for compliance.

FAQ: Voltage Drop Calculator

What is voltage drop?

Voltage drop is the reduction in voltage in an electrical circuit between the source and the load due to resistance in the wire.

How can I reduce voltage drop?

Use thicker cables, shorten the wire length, or lower the circuit current.

Where do I get resistance values?

Check the manufacturer specs of your cable, or use typical values like:

  • Copper = ~0.017 Ω/m
  • Aluminum = ~0.028 Ω/m

What’s an acceptable voltage drop?

  • Typically, less than 5% is acceptable for general use.
  • Sensitive equipment may require <3%.

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