Engineering & Electronics

Free Wire Voltage Drop & Size Calculator

Ensuring proper conductor sizing is critical for electrical safety, NEC code compliance, and preventing equipment overheating. Our free voltage drop calculator wire computes electrical voltage drop (Vdrop) and percentage loss across copper or aluminum conductors. Calculate calculate wire voltage drop awg size requirements for AC single-phase, 3-phase, and DC solar or automotive circuits.

Wire Voltage Drop & Size Calculator

Calculate AC/DC wire voltage drop, AWG size & percentage loss

Voltage (V)

Current (Amps)

Distance (One-way Feet)

Wire Gauge (AWG Size)

Conductor Material

Voltage Drop & Loss

Voltage Drop: 5.93 V (4.94%)

Final Voltage at Load: 114.07 V

NEC Standard Status: ⚠️ Acceptable (< 5%)

Mathematical Formulas & Calculation Methods

Single-Phase & DC Voltage Drop Formula

Calculates voltage drop for 2-wire AC or DC circuits using the ac dc voltage drop calculator.

Vdrop = (2 × K × I × L) ÷ Circular Mils

3-Phase Voltage Drop Formula

Calculates line-to-line voltage drop for 3-phase power circuits using the 3 phase voltage drop calculator.

Vdrop = (√3 × K × I × L) ÷ Circular Mils

Percentage Voltage Loss Formula

Calculates percentage loss relative to initial source voltage using our voltage drop percentage loss finder.

% Drop = (Vdrop ÷ Source Voltage) × 100%

Worked Step-by-Step Examples

Example 1: 120V 15A Branch Circuit (100 ft, 12 AWG Copper)

"Calculate voltage drop for a 120V, 15-Amp circuit running 100 feet over 12 AWG copper wire. <strong>how to calculate wire size voltage drop</strong>."

Steps:

Copper resistivity K ≈ 12.9.
12 AWG circular mils = 6,530 CM.
Vdrop = (2 × 12.9 × 15 × 100) ÷ 6,530 = 38,700 ÷ 6,530 = 5.93V.
% Drop = (5.93 ÷ 120) × 100 = 4.94%.

Result: Voltage drop is 5.93V (4.94% drop, leaving 114.07V at load).

Example 2: 240V 3-Phase Commercial Feeder (200 ft, 4/0 AWG)

"Find voltage drop for 240V 3-phase, 100 Amps, 200 feet, 4/0 AWG copper."

Steps:

4/0 AWG circular mils = 211,600 CM.
Vdrop = (1.732 × 12.9 × 100 × 200) ÷ 211,600 = 446,856 ÷ 211,600 = 2.11V.
% Drop = (2.11 ÷ 240) × 100 = 0.88%.

Result: Voltage drop is 2.11V (0.88% drop, excellent NEC compliance).

What is Wire Voltage Drop & Size Calculator?

A voltage drop calculator wire computes the reduction in electrical potential as electric current flows through conductor resistance.

The National Electrical Code (NEC) recommends a maximum voltage drop of 3% on branch circuits and 5% total overall feeder/branch combined.

How to Use Wire Voltage Drop & Size Calculator

1Select circuit type (DC, AC Single-Phase, or AC 3-Phase).
2Enter source voltage, load current (Amps), and one-way wire distance (feet or meters).
3Select wire gauge (AWG) and conductor material (Copper or Aluminum).
4View instant voltage drop, percentage loss, and final load voltage.

Key Features

Supports AWG wire sizes from 14 AWG up to 1000 kcmil.
Copper and aluminum conductor resistivity options.
AC single-phase, 3-phase, and DC circuit calculations.
NEC 3% and 5% compliance status indicators.
100% free online calculator for electrician tools.

Benefits of Using Wire Voltage Drop & Size Calculator

Ensures electrical installations comply with NEC building codes.

Prevents motor burnout and voltage dips at remote loads.

Saves money by selecting the optimal wire AWG gauge.

Works on mobile phones for field electricians.

Practical Use Cases

Electricians & Contractors

Size feeders and subpanels to satisfy copper wire voltage drop solver guidelines.

Solar Installers

Size DC PV array cables to minimize power loss.

Electrical Engineers

Design commercial power distribution circuits.

DIY Homeowners

Calculate wire requirements for outdoor sheds and EV chargers.

Frequently Asked Questions

What is acceptable voltage drop according to the NEC?

The NEC recommends a maximum of 3% on branch circuits and 5% combined overall feeder/branch drop using our electrical cable voltage drop formula.

Does wire length increase voltage drop?

Yes. Longer distances increase total conductor resistance, resulting in higher voltage drop.

Why use aluminum wire instead of copper?

Aluminum wire is cheaper and lighter for large feeders, but requires larger AWG gauge size due to higher resistivity.

Is this voltage drop calculator free?

Yes, this voltage drop calculator wire is 100% free.

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