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Cable Voltage Drop Calculator

Estimate cable voltage drop, delivered voltage and conductor losses for DC and AC circuits.

Input Parameters

The positive and return conductors are both included in the circuit drop.

Equivalent area: 2.5 mm²

Enter source-to-load distance. The calculator doubles it to include the return conductor.

Circuit Diagram

DCDC source230 VCABLE+−LOAD10 AONE-WAY • 10 mRETURN FACTOR APPLIED

Equations

Rϕ=ρLAR_\phi=\rho\dfrac{L}{A}
ΔV=2IρLA\Delta V=2I\rho\dfrac{L}{A}
Ploss=2I2ρLAP_{loss}=2I^2\rho\dfrac{L}{A}

Calculated Values

Cable voltage drop1.3792 V
Loss versus source0.6 %
Material resistivity at 20 °C1.724E-8 Ω·m
Voltage at load228.6208 V
Power lost in cable13.792 W
Circuit resistance137.92 mΩ
Preliminary recommended section2.5 mm²
Recommendation selects the next standard section meeting a 3% design voltage-drop target and 4 A/mm² current-density screen. Verify final ampacity against local regulations, insulation temperature, installation method, ambient temperature and cable grouping.

Resistivity values are typical at 20 °C and match the site's resistivity table. AC reactance, power factor effects and conductor heating are not included.

Cable guide

Assess voltage drop before choosing a cable

A cable has resistance and dissipates power. A conductor that seems adequate for current can still create unacceptable voltage drop at the load, especially at low voltage and over distance.

Method and assumptions

The calculation uses resistivity, round-trip length, cross-section, and current. DC, single-phase, and three-phase modes apply different path assumptions that must match the real installation.

Inputs to verify

Circuit length

Check whether the tool expects one-way distance or total path; an error here can easily double calculated drop.

Current and material

Use the sustained maximum current and resistivity compatible with the material and operating temperature.

Recommended workflow

  1. 1Define nominal voltage, maximum current, and physical installation length.
  2. 2Compare voltage drop in volts and percent with the load’s budget.
  3. 3Also validate ampacity, temperature, protection, and standards applicable to the installation.

Decision example

In a 12 V system, a few tenths of a volt can already disturb a sensitive load. Set an allowable drop before selecting cross-section instead of considering nominal current alone.

Limits to keep in mind

The result is not a regulatory cable design. It does not replace applicable ampacity, short-circuit, installation, grouping, protection, or fire rules in your country.

Frequently asked questions

Why count the round trip for DC?

Current travels in the outgoing conductor and returns through another conductor; both resistances contribute to total drop.

Does a larger cross-section improve everything?

It reduces resistance and voltage drop, but cost, bend radius, terminals, and installation rules still matter.

References to consult

  • Method references: conductor resistivity, IEC 60364 / local rules, and the cable datasheet for ampacity and temperature.

Original educational content, reviewed for technical clarity on 20 August 2026. Always verify datasheets, applicable standards, and your design before power-up or manufacture.