Electrical systems • Cable comparison
Cable Voltage Drop Comparison Calculator
Compare two or three conductor options for steady-state AC voltage change. Enter guide assumptions or manufacturer R/X data; the tool does not select a cable.
Circuit and cable data
Comparison result
Use the example values or enter your circuit and cable data.
Read the signed ΔU directly: a negative value is calculated voltage rise. Verify applicable manufacturer data, conductor temperature, installation conditions and project requirements separately.
Formula and sign convention
Z term = R × PF + X × sin φ. Lagging sin φ is positive; leading sin φ is negative. Single-phase 2-wire: ΔU = 2 × I × Z term × L. Balanced three-phase: ΔU = √3 × I × Z term × L. Percentage = ΔU ÷ system voltage × 100; receiving voltage = system voltage − ΔU.
Guide estimate assumptions
Guide mode uses R = 23.7/S Ω/km for copper or R = 37.6/S Ω/km for aluminium and X = 0.08 Ω/km, where S is CSA in mm². These are simplified planning inputs, not cable-specific manufacturer data.
Limits
Steady-state AC only. This calculator does not model conductor operating temperature, harmonics, parallel conductors, unbalanced systems, neutral current, cable construction, joints, source impedance, ampacity, derating, protective devices, short circuit, starting current or local-code compliance. A comparison result is not a safe, suitable, recommended or compliant cable selection.
Sources
Reviewed 2 September 2026:
Use this calculator to compare candidate cable sizes using your own load, cable length and installation inputs. Review the estimated voltage drop, percentage drop, conductor loss and running-cost effect side by side before narrowing the options.
What to enter
Use project-specific electrical values and installation details. Check the units before calculating, and compare like-for-like cable options. The template controls the available fields and calculations; this supporting copy does not replace those labels or the underlying logic.
How to use the comparison
Treat the output as a planning comparison, not as final cable selection. A lower estimated drop or loss does not by itself confirm ampacity, fault protection, installation method, derating, termination suitability or compliance.
Before selecting a cable
Verify the actual route length, load conditions, conductor material, installation environment and applicable requirements. Have a qualified electrical professional check the final cable size, protection and installation before purchase or connection.