Voltage Drop Calculator – Calculate Wire Voltage Drop Easily Online

Intro

A Voltage Drop Calculator is a handy online tool that helps electricians, engineers, and DIY enthusiasts determine the loss of voltage in an electrical circuit. When current flows through a wire, some energy is lost due to resistance, resulting in a lower voltage at the end of the circuit compared to the source.

Excessive voltage drop can cause electrical equipment to malfunction, lights to dim, or even lead to overheating and safety hazards. That’s why calculating voltage drop is crucial for designing safe and efficient wiring systems.

With the Voltage Drop Calculator online, you can quickly determine whether your wire size and length are sufficient for your electrical load—without doing manual calculations.

---

Formula / Working

Voltage drop is calculated using Ohm’s Law and the resistance of the conductor.

The general formula is: Vd=2×L×I×R1000V_d = \frac{2 \times L \times I \times R}{1000}Vd​=10002×L×I×R​

Where:

• VdV_dVd​ = Voltage drop (Volts)
• LLL = One-way length of the conductor (meters or feet)
• III = Current (Amps)
• RRR = Resistance per unit length of the conductor (Ohms per 1000 units)

Another simple relation: Vd=I×RtotalV_d = I \times R_{total}Vd​=I×Rtotal​

And the percentage voltage drop is: %Vd=VdVsource×100\%V_d = \frac{V_d}{V_{source}} \times 100%Vd​=Vsource​Vd​​×100

This tells you how much of the supply voltage is lost along the wire.

---

Step-by-Step Usage

Using the Voltage Drop Calculator online is simple:

1. Enter the conductor length (in meters or feet).
2. Input the current (Amps) your circuit is carrying.
3. Select the wire size (AWG or mm²) and material (copper or aluminum).
4. Enter the supply voltage (like 120V, 230V, or 400V).
5. Click Calculate to get results for voltage drop in volts and percentage.

---

Examples

Example 1: Residential Circuit

• Wire length: 30 meters
• Load current: 10 Amps
• Wire: Copper, 2.5 mm²
• Source voltage: 230V

Calculation:

• Resistance ≈ 7.41 Ω/km (for 2.5 mm² copper)
• Voltage Drop = (2 × 30 × 10 × 7.41) / 1000 = 4.45V
• % Drop = (4.45 ÷ 230) × 100 = 1.93%

✅ Result: Safe. Voltage drop is under 5%.

---

Example 2: Industrial Circuit

• Wire length: 100 meters
• Load current: 50 Amps
• Wire: Aluminum, 16 mm²
• Source voltage: 400V

Calculation:

• Resistance ≈ 1.91 Ω/km (for 16 mm² aluminum)
• Voltage Drop = (2 × 100 × 50 × 1.91) / 1000 = 19.1V
• % Drop = (19.1 ÷ 400) × 100 = 4.77%

✅ Result: Acceptable, but close to the 5% maximum recommended drop.

---

Example 3: Lighting Circuit

• Wire length: 50 meters
• Load current: 5 Amps
• Wire: Copper, 1.5 mm²
• Source voltage: 120V

Calculation:

• Resistance ≈ 12.1 Ω/km (for 1.5 mm² copper)
• Voltage Drop = (2 × 50 × 5 × 12.1) / 1000 = 6.05V
• % Drop = (6.05 ÷ 120) × 100 = 5.04%

⚠️ Result: Slightly above recommended. Consider thicker wire.

---

FAQs

1. What is a voltage drop?
Voltage drop is the reduction in voltage as electricity travels through a conductor due to resistance.

2. Why should I calculate voltage drop?
Because excessive voltage drop can cause equipment damage, energy loss, and safety issues.

3. What is the acceptable voltage drop?
In most electrical standards, 3% is recommended for lighting circuits and 5% for other circuits.

4. Does wire material affect voltage drop?
Yes. Copper has lower resistance than aluminum, so it experiences less voltage drop.

5. How can I reduce voltage drop?

• Use thicker wires
• Shorten wire runs
• Use copper instead of aluminum
• Balance loads across circuits