ONLINToolsPremium Suite

Voltage Drop Calculator

Estimate circuit voltage drop using wire size, material, current, phase type, and run length. Compare drop percentage and get a quick wire size suggestion for your target.

Circuit Inputs
Set electrical and cable parameters for drop estimation.

Estimated Voltage Drop

8.991 V

3.75% of source voltage

Voltage at load

231.009 V

Drop percentage

3.75%

Power loss

269.7 W

Wire resistance

0.999 Ω/1000ft

Recommended AWG for Target Drop
Based on current, voltage, length, and selected conductor material.

Suggested minimum wire size to stay under 3%: 4/0 AWG (107 mm²).

Voltage Drop Formulas
Core equations used by this calculator.

Vdrop = 2 × I × R × L (DC / single-phase)

Vdrop = sqrt(3) × I × R × L (three-phase)

Drop% = (Vdrop / Vsource) × 100

Vload = Vsource - Vdrop

Here, R is conductor resistance in ohms per 1000 ft and L is one-way length in thousands of feet.

What Changes Voltage Drop?
Design factors that raise or reduce drop.
Length: Longer runs increase total resistance and drop.
Current: Higher load amps produce higher voltage drop.
Wire size: Larger conductors have lower ohms and lower drop.
Material: Copper generally drops less voltage than aluminum at the same size.
How to Use This Voltage Drop Calculator
Fast 4-step method for branch circuits and feeders.
1

Enter source voltage and load current.

2

Select phase type (DC, single-phase AC, or three-phase AC).

3

Choose conductor material and AWG size.

4

Input one-way run length and check drop percentage against your design target.

Common AWG Reference (Quick Table)
Typical copper resistance values used for fast estimation.
AWGArea (mm²)Copper (Ω/1000ft)Aluminum (Ω/1000ft)
4/01070.0490.079
3/0850.0620.1
2/0670.0780.126
1/053.50.0980.158
142.40.1240.199
233.60.1560.252
326.70.1970.317
421.20.2490.401
613.30.3950.637
88.370.6281.014
105.260.9991.612
123.311.5882.563
142.082.5254.078
Voltage Drop FAQ
Practical answers for wiring design and planning.

Need related tools? Try Unit Converter, Scientific Calculator, and Work Days Calculator.

Related Tools
Explore other useful calculator tools

Unit Converter

Convert length and electrical-related units quickly.

Scientific Calculator

Evaluate formulas and advanced expressions.

Bandwidth Calculator

Estimate transfer and capacity with clear units.