Case 1: Single-phase 200V / 20A / 30m / Cu 25mm2
Input
Circuit=single, V=200, I=20, L=30, material=Cu, temp=60, pf=1.0, standard=IEC, size=25, allowable=3.0%
Output
ΔV=0.96V, ΔV%=0.48%, Pass
Voltage Drop Calculator (Quick) + Cable Size Guide
Calculate voltage drop (V / %) from voltage, current, distance, and conductor conditions.
The allowable threshold is shown as reference Pass/Warn only. When a standard set is selected, cable candidates are listed from the voltage-drop perspective.
Distance handling is always visible (single: 2L / three-phase: L)
Choose resistance by preset or manual input
Copy result text and share by URL
How to use
- Choose circuit type (single-phase or three-phase), then enter voltage, current, and one-way distance.
- Set conductor material (Cu/Al), conductor temperature, and power factor.
- Choose resistance by preset (standard + size) or manual value.
- Enter allowable voltage-drop % and review ΔV / % / Pass-Warn in the result card.
- Use copy result or share URL when needed.
Sample
Case 2: Three-phase 400V / 80A / 80m / Al 16mm2
Input
Circuit=three-phase, V=400, I=80, L=80, material=Al, temp=60, pf=0.9, standard=IEC, size=16, allowable=3.0%
Output
ΔV=20.40V, ΔV%=5.10%, Warn
Formulas (Quick)
- R(T) = R(20) × (1 + α × (T - 20))
- Single-phase (2-wire): ΔV = 2 × I × R(T) × L[km] × pf
- Three-phase (3-wire): ΔV = sqrt(3) × I × R(T) × L[km] × pf
- ΔV% = (ΔV / V) × 100
FAQ
Should I enter round-trip distance?
No. Enter one-way distance. Internally, single-phase uses round-trip (2L) and three-phase uses one-way (sqrt(3) formula).
Does Pass mean code compliance?
No. Pass/Warn is a reference comparison only. Always prioritize regulations, internal standards, design documents, and manufacturer data.
When should I use manual resistance instead of preset?
Use manual input when you have manufacturer or design-sheet resistance values. Preset values are area-based approximations.
What changes when power factor is not 1.0?
In this quick model, the resistive drop is adjusted by cosphi. Reactance is not included.
Notes
- This tool is for reference calculation. Prioritize regulations, standards, design documents, and manufacturer data.
- The equation is resistive and simplified. Reactance, installation conditions, ampacity, short-circuit, and protection coordination are not considered.
- Distance input is one-way. Single-phase uses round-trip (×2), three-phase uses one-way (sqrt(3) formula).