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- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The voltage drop calculator determines voltage loss in copper wires, common in electrical installations. It uses the formula ΔV = 2·ρ·L·I/S, where ρ is copper's resistivity (0.0172 Ω·mm²/m), L the cable length in meters, I the current in amps, and S the cross-sectional area in mm². The factor 2 accounts for the round-trip circuit path.
This tool is essential for sizing wires in residential, industrial, or commercial setups to ensure devices receive adequate voltage. Example: For a 100-meter installation with 10 A current and 2.5 mm² wire, the calculated drop shows if the wire gauge needs adjustment to avoid overloading.
CAUTION: The resistivity here is specific to copper. Use ρ = 0.0282 Ω·mm²/m for aluminum. Temperature also slightly affects resistivity, but this basic calculation ignores it. High-current or long-distance installations should consult an engineer for advanced technical details.
Frequently asked questions
What is this calculator for?
It calculates voltage loss in copper wires to help size cables in electrical installations.
Does the formula account for wire thickness?
Yes, the cross-sectional area (S) directly affects the result: thicker wires reduce voltage drop.
Can I use it for aluminum?
Not directly. Replace copper's resistivity (ρ) with 0.0282 Ω·mm²/m for aluminum cables.
When is voltage drop critical?
In long circuits or high-current applications like apartment power lines or industrial equipment.
Should I consider temperature?
The basic formula doesn't include it, but in very hot environments, copper's resistivity increases slightly, altering the result.