Cable Sizing Calculator
Estimate the minimum cable cross-section for LV installations using load current, installation method, number of circuits, ambient temperature and voltage drop constraints.
This is a simplified first-pass estimator. Real designs must include protective device coordination, short-circuit withstand, number of loaded conductors, insulation type, group derating tables and local standards (IEC 60364, NEC, HD 60364, etc.).
Overview
LV cable selection is a two-step problem: (1) choose a cross-section with enough ampacity for the load current under the real installation conditions (derating for grouping, ambient temperature, installation method), and (2) verify that the voltage drop stays within the allowed limit for the circuit length.
Our tool gives a quick estimate for both conditions using simplified derating curves and the standard drop model. The final choice must always be cross-checked against the full tables in IEC 60364, NEC, NF C 15-100, DIN VDE or whatever applies locally.
Don’t forget that AWG ↔ mm² conversion and voltage drop are closely linked steps — we recommend you run all three calculators in sequence before printing a datasheet or a Bill of Quantities.
How it works
- 1. Describe the loadVoltage, power and cos φ to obtain operating current Iop.
- 2. Describe the installationMaterial, method, grouping and ambient for derating.
- 3. Enforce the drop limitIterate the section until Vd % ≤ allowed threshold.
- 4. Take the maxFinal size = max(section by ampacity, section by drop).
FAQ
Is this compliant with IEC 60364?+
It is an early estimate. Always confirm with the standard’s derating tables and short-circuit thermal constraints.
Why recommend a larger size than ampacity?+
Because drop limits increase sharply with distance — this is the classic trade-off in LV layouts.
Parallel cables: what changes?+
The derating here is a rough model; real tables require grouping factor k for n circuits per installation method.