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Cable Size Calculator — Voltage Drop & Entered Ampacity
Estimate a conductor-size candidate from your chosen voltage-drop limit, with an optional check against your own manufacturer ampacity table.
ELECTRICAL TOPICCable Size Calculator
Your result
CABLE PLANNINGREADY
—Enter values below and press Calculate.
RESULT DISPLAYA + m → mm²
Calculation details & exports
Inputs used
Formula and worked example
ΔV = k × I × L × ρ / A; Amin = k × I × L × ρ / ΔVallowed. k = 2 for single-phase/DC, √3 for balanced three-phase. L is one-way metres. ρ = 0.0237 (Cu) or 0.0376 (Al) Ω·mm²/m for the normal-service approximation. Optional thermal check: Iz × derating ≥ I.
Worked example
At 230 V, 20 A, 30 m one-way, copper and a chosen 3% limit: Amin = 4.1217 mm². The next displayed standard area is 6 mm², giving 4.74 V / 2.0609% drop in this resistive model. Thermal capacity has not been established by that result.
Using this tool
Enter the actual equipment and project values. The Use example button loads an illustrative case. Calculation happens in your browser; no Python, API key or account is required. Use the result details to see the inputs and scope, copy the result, download CSV or print.
यह पहले voltage-drop के हिसाब से न्यूनतम area निकालता है। केवल mm² दिखने का अर्थ पूरी cable selection या safety approval नहीं है। Ampacity के लिए सही manufacturer table और correction factors दें।
Common questions
Does the displayed size mean the cable is safe to install?
It is a planning candidate within the stated model. Ampacity, protective-device coordination, fault withstand, earth/neutral sizing and actual installation conditions require separate verification.
Why is cable reactance not used?
This first model uses PF = 1 and X = 0 with a normal-service resistance approximation. For appreciable reactance, poor power factor or large conductors, use applicable datasheet R/X and a full installation calculation.
What happens if no size meets my table?
The display reports no candidate. It does not extrapolate ampacity or invent a larger approved conductor.
Related practical guides
Other calculators
Formula references and model scope
Formula review: 2 November 2026. Examples are illustrative. Enter project-specific data; a planning result does not certify an installation or equipment selection.
