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Electrical Tool

Voltage Drop Calculator

Estimate voltage drop for copper and aluminium conductors using circuit type, voltage, current, cable length and conductor cross-section.

Updated: June 7, 2026Planning reference

Quick Answer

Check voltage drop before using long cable runs for infrastructure equipment.

Enter circuit type, voltage, current, cable length, conductor material and cross-section. The calculator estimates voltage drop, voltage at load, cable resistance, power loss and whether the result is within the selected target.

Circuit Setup

Input values

Use practical planning values. Final design must be verified against applicable IEC/DIN/VDE/NEC requirements, local rules, installation method and project specifications.

Electrical System

Cable Run

Formula basis

DC and single-phase circuits use a 2 × length loop factor. Three-phase circuits use √3 × length. This calculator uses a simplified resistive voltage-drop estimate.

Formula / Method

What the calculator does

The calculator estimates conductor resistance from material, length and cross-section, then calculates voltage drop, voltage at load and power loss for the selected circuit type.

Voltage drop = current × conductor resistance

Inputs

Required inputs

Use circuit type, conductor material, voltage, current, cable length, cross-section, power factor and target maximum voltage drop.

Uses

Where this helps

Useful for rack circuits, long cable runs, technical rooms, small distribution checks, infrastructure equipment planning and early electrical coordination.

FAQ

Voltage-drop notes

Can this replace electrical design?

No. It is a planning calculator only. Final conductor sizing and protection must be checked by qualified review and local electrical requirements.

Why does cable length matter so much?

Longer cable routes increase conductor resistance. Higher resistance creates more voltage drop and higher power loss.

What target voltage drop should I use?

Many planning checks use around 3% for final circuits, but the correct target depends on local rules, installation standards, load type, voltage level and project requirements.

Learn More

Reference links

Project

Need help validating cable runs or circuit planning?

ITCOREOPS can support electrical coordination, rack power review, structured cabling, documentation, labeling, testing and infrastructure handover.

Open project formVisit ITCOREOPS →

Disclaimer

Planning reference only

This calculator provides a simplified planning estimate only. It does not replace qualified electrical design, IEC/DIN/VDE/NEC review, local regulations, conductor derating, protection-device review, manufacturer documentation or professional inspection.

Workflow

Voltage drop should be checked before long cable runs are accepted.

Use this calculator before assigning equipment to long cable runs, planning rack power, or documenting early electrical coordination notes.

Use exact inputs ↑

Support

Need help with infrastructure planning?

For rack power, structured cabling, electrical coordination and operational infrastructure support, visit ITCOREOPS.

Visit ITCOREOPS →Email ITCOREOPS ✉

Feedback

Found a bug or result issue?

Report display problems, calculation issues or suggestions for improving this calculator.

Report a bug ✉

Worked example

Inputs: three-phase feeder, 32 A at 400 V, 50 m of 6 mm² copper, cos φ = 1.0.

Formula: ΔU = (√3 × L × I × cos φ) ÷ (γ × A), copper γ = 56 m/(Ω·mm²).

Result: ΔU = (1.732 × 50 × 32) ÷ (56 × 6) ≈ 8.2 V (≈ 2.1 %) — within the 3 % limit for final circuits.