Voltage Drop Calculator

Precision calculation for AC and DC electrical systems.

System Type

Material

Voltage (V)

Current (Amps)

Wire Size (AWG / mm²)

Distance

Unit

Voltage Drop: 0.00 V

Drop Percentage: 0.00 %

Voltage at Load: 0.00 V

Mathematical Formulas Used

For DC and AC Single-Phase:

V_drop = (2 × L × R × I) / 1000

For AC Three-Phase Systems:

V_drop = (1.732 × L × R × I) / 1000

Supported Cable Sizes

14 AWG (2.08 mm²)

12 AWG (3.31 mm²)

10 AWG (5.26 mm²)

8 AWG (8.37 mm²)

6 AWG (13.3 mm²)

4 AWG (21.2 mm²)

3 AWG (26.7 mm²)

2 AWG (33.6 mm²)

1 AWG (42.4 mm²)

1/0 AWG (53.5 mm²)

2/0 AWG (67.4 mm²)

3/0 AWG (85.0 mm²)

4/0 AWG (107 mm²)

250 kcmil (127 mm²)

300 kcmil (152 mm²)

350 kcmil (177 mm²)

400 kcmil (203 mm²)

500 kcmil (253 mm²)

600 kcmil (304 mm²)

750 kcmil (380 mm²)

1000 kcmil (507 mm²)

Use this Voltage Drop Calculator for AC & DC systems. Supports Copper/Aluminum wire sizes 14 AWG(2 mm²)up to 1000 kcmil(500 mm²). Ensure NEC 3% limit compliance

What is Voltage Drop?

Voltage drop is the decrease in electrical potential as current flows through a conductor. Because every wire has a specific amount of resistance, some energy is lost as heat. If the voltage drops too significantly, equipment can malfunction, motors can overheat.

Key Options and Features of this Voltage Drop Calculator

This Voltage Drop Calculator is built with a wide array of options to handle diverse electrical scenarios:

System Type: Supports DC (Direct Current), AC Single Phase for residential use, and AC Three Phase for industrial applications.
Conductor Material: Choose between Copper (Cu) or Aluminum (Al).
Extensive Wire Sizes: Includes standard AWG (American Wire Gauge)and Metric( $m m^{2}$ ) sizes from 14 AWG ( $2.08 m m^{2}$ )up to massive 1000 kcmil ( $507 m m^{2}$ )industrial cables.
Unit Flexibility: Switch between Feet (ft) and Meters (m) depending on your project requirements.
Safety Logic: Automatically flags calculations that exceed the NEC (National Electrical Code) recommended 3% limit.

How to Use this Voltage Drop Calculator

Using the Voltage Drop Calculator is straightforward. Follow these steps for an accurate result:

Step 1: Select your System Type (DC (Direct Current), AC Single Phase, or AC Three Phase).
Step 2: Choose your Conductor Material (Copper is standard for most indoor wiring).
Step 3: Enter the Source Voltage (e.g., 12V, 120V, 240V, or 480V).
Step 4: Input the Current in Amps (The maximum load the wire will carry).
Step 5: Open the dropdown menu and select your cable size. You will see the AWG/kcmil size followed by its Metric equivalent in $m m^{2}$ in brackets.
Step 6: Enter the One-way Distance of the wire run.
Step 7: Click Calculate Drop to see the results.

AWG to Metric ( $m m^{2}$ ) Conversion for Voltage Drop

Electrical standards vary by region. While the US primarily uses AWG, many other countries use square millimeters ( $m m^{2}$ ). Our tool simplifies this by providing both measurements in the same interface, ensuring that whether you are using a 10 AWG or a $6 m m^{2}$ wire, your voltage drop calculations remain precise and code-compliant.

Supported System

For Calculate voltage drop, Drop Percentage, Voltage at Load, this Voltage Drop Calculator support these systems.

DC (Direct Current)

AC Single Phase

AC Three Phase

How this Voltage Drop Calculator Works: Software Logic

When you click calculate, the tool performs a Table Lookup for the specific resistance of your selected wire size and material based on the NEC 75°C standard. It then converts your units to feet (if necessary) and applies the phase multiplier ( $2$ or $1.732$ ). Finally, it calculates the Voltage at Load by subtracting the drop from the source, giving you a clear picture of how much power reaches your device.

Examples of this Voltage Drop Calculator

Example 1: DC System

System Type: DC (Direct Current)
Source Voltage: 12V
Load Current: 20 Amps
Wire Size: 10 AWG (5.26 $m m^{2}$ ) Copper
Distance (One-way): 25 Feet
The Calculation: The tool uses the resistance for 5.26 $m m^{2}$ ( $1.21Ω$ ) and the DC factor of 2.
Result: Voltage Drop: 1.21V (10.08%)
Analysis: WARNING. A 10% drop is far too high for a 12V system. The battery will not charge properly. To fix this, you should upgrade to a thicker 4 AWG (21.2 $m m^{2}$ ) wire to keep the drop under the 3% limit.

Example 2: AC Three-Phase

System Type: AC Three-Phase
Source Voltage: 480V
Load Current: 50 Amps
Wire Size: 4 AWG (21.2 $m m^{2}$ ) Copper
Distance (One-way): 200 Feet
The Calculation: The tool uses the resistance for 21.2 $m m^{2}$ ( $0.308Ω$ ) and the Three-Phase factor of 1.732.
Math:
Result: Voltage Drop: 5.33V (1.11%)
Analysis: PASS. A drop of 1.11% is excellent. This ensures the industrial motor receives stable power and operates at peak efficiency without overheating.

Example 3: AC Single-Phase

System Type: AC Single-Phase
Source Voltage: 240V
Load Current: 30 Amps
Wire Size: 10 AWG (5.26 $m m^{2}$ ) Copper
Distance (One-way): 100 Feet
The Calculation: The tool uses the resistance for 5.26 $m m^{2}$ ( $1.21Ω$ ) and the AC factor of 2.
Result: Voltage Drop: 7.26V (3.03%)
Analysis: PASS (Borderline). This result is right at the NEC recommended limit of 3%. While technically safe, if the distance were any longer, you would need to switch to an 8 AWG (8.37 $m m^{2}$ ) wire to maintain optimal performance for your machinery.