Cable Cross-Section Calculator
Calculate copper and aluminum cable cross-section by load: current, power, length, and allowable voltage drop. Single-phase and three-phase networks.
Conductor material
Network type
Total power of the appliances on this cable
220 V for single-phase, 380 V for three-phase
Use 0.95 for household load, 1 for resistive (heater, lamps)
Distance from the panel to the farthest load
Building codes — up to 5%; for lighting circuits — 3%
Calculation formula
S = (2 × ρ × L × I) / (U × ΔU%/100)
ρ — resistivity (copper 0.0175, aluminum 0.028), L — length, I — current, U — voltage, ΔU% — allowable drop. Current I = P×1000 / (U × cos φ) for single-phase, divided by √3 for three-phase.
About the cable cross-section calculator
The calculator picks a conductor cross-section by load: it derives the current from power and voltage, then uses cable length and allowable voltage drop to find the required area, rounding up to the nearest standard size from the 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50 mm² series.
Both copper (ρ=0.0175 Ω·mm²/m) and aluminum (ρ=0.028 Ω·mm²/m) are supported, along with single-phase 220 V and three-phase 380 V networks. The power factor cos φ is included — use 1 for resistive loads and 0.95 for typical household loads.
All math runs locally in your browser using the standard electrical formula. Results are practical for picking PVC, NYM, or rubber cables for a service entrance, an outlet group, or a dedicated appliance line.
Benefits
Copper and aluminum
Correct resistivity for both conductor materials.
Single- and three-phase
The √3 factor for 380 V and cos φ for reactive loads toggle in one click.
Rounding to standard sizes
Results are rounded up to standard 1.5–50 mm² sizes that you can actually buy in a store.
Frequently asked questions
Should I pick copper or aluminum?
Indoor wiring in residential buildings should be copper — it is more reliable at terminations and carries roughly 1.6 times the current of aluminum at the same cross-section. Aluminum is used for service drops, feeders, and overhead lines because it is cheaper and lighter, but needs a larger cross-section.
Is the allowable voltage drop 3% or 5%?
Total drop from the transformer to the farthest point should stay under 5%. Lighting circuits use a tighter 3% margin so lamps do not dim when heavy appliances switch on.
VVG or NYM cable — which one?
VVG (VVGng-LS in particular) is the standard low-smoke flame-retardant cable for concealed wiring in apartments. NYM is its German equivalent with extra chalk-filled inner sheath that strips more cleanly during installation. The cross-section from this calculator works for both.
What gauge for an LED strip?
Most 12/24 V LED strips up to 60 W run on 0.75–1.5 mm² copper wire. For long runs, calculate by DC current: I = P / U, and keep the drop under 5% — otherwise the far end of the strip will visibly fade in color and brightness.
How do I pick the breaker for a given cross-section?
The breaker must trip before the cable overheats. For copper: 1.5 mm² → 10 A, 2.5 mm² → 16 A, 4 mm² → 25 A, 6 mm² → 32 A, 10 mm² → 40–50 A. For aluminum, drop one step.