↘️ Voltage Drop Calculator for Electrical
Estimate conductor voltage drop from current, length and resistance.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the Voltage Drop calculator →
How to calculate voltage drop
Method: Voltage drop = current × round-trip conductor resistance
- Use maximum expected current.
- Use one-way route length and the correct loop treatment.
- Apply conductor resistance for material, size and temperature, then compare percentage drop with the design limit.
Worked example
Using these planning inputs:
- Load current: 10 A
- One-way cable length: 15
- Conductor resistance: 7.41 Ω/km
- Supply voltage: 12 V
Estimated voltage drop: 2.223 V
Reality check: This is not a cable-sizing approval tool; heating, fault current, protection, grouping, insulation and regulatory limits also control selection.
Method status and references
Loop-resistance estimate. Vaelden doubles the entered one-way length so both outgoing and return conductors are included. Temperature and installation rules still require design checks.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.