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    Interactive calculator

    LV Cable Sizing

    Get a preliminary minimum Cu/Al cable recommendation from current, length, PVC/XLPE and installation method; compare parallel runs and explore the math.

    EstimatePreliminary result, not a design verification.
    Before you calculate

    Understanding LV cable sizing

    Enter current, distance and cable type to find a preliminary minimum conductor size using IEC-based reference ratings. Then review current capacity, voltage drop, parallel runs and the remaining protection checks.

    Learn more — illustrated guide →
    Step 1 · Quick cable selection

    What cable do I need?

    Enter your load current and feeder length. KiloVolt checks current-carrying capacity and voltage drop to suggest a preliminary cross-section for the selected installation method. Only PHASE conductor sections are recommended; individual conductors are capped at 300 mm². No manufacturer catalogue, neutral or protective-conductor sizing is applied. B2 (conduit/trunking) is the initial example, not a substitute for identifying your actual cable route.

    Critical: B2 is conduit/trunking; C is clipped direct. Thermally insulated walls (A2), buried routes and many other cases are not supported by quick mode.
    Automatic selects one run for small circuits and adds parallel runs when needed. Choose a fixed count only when you want to check a particular arrangement.
    Additional calculation settings Power factor, temperature, voltage-drop limit
    Design preference, NOT an IEC requirement. Practical choices need at least this spare corrected ampacity.
    Illustrative; affected by geometry and installation.
    Step 2 · Preliminary recommendation
    Enter a valid design current above 0 A and up to 1,500 A, along with the remaining circuit values.
    Advanced cable verificationManual reference ampacity, breaker coordination, short-circuit thermal checks

    The original v0.1.11 verification calculator is preserved here. It lets you check a specific cable using manufacturer data and your actual protection and grouping factors. The quick recommendation above does not automatically verify these advanced requirements.

    Step 1 · Circuit & conductor

    Define your LV feeder

    Check an existing cable selection, including multiple identical runs per phase. Values update instantly.

    Example: 3 × 240 mm² per phase. Current is the TOTAL feeder current.
    Illustrative default; actual cable layout matters.
    Step 2 · Installation conditions

    Current-carrying capacity

    For reliable IEC-based ampacity checking, use the cable manufacturer’s rated current or an authorized standards table for the actual installation method. KiloVolt does not guess this value.

    Documentation only; does not automatically choose an ampacity table.
    Leave blank until you have the correct table or datasheet.
    1.00 assumes reference conditions.
    Enter a factor suitable for the complete cable arrangement.
    For applicable additional corrections; otherwise 1.
    Optional; required for protective-device check.
    Optional. Use the actual device’s value; e.g. 1.45 is not universal.
    Parallel cable warning: If other circuits share the same route, grouping derating may still apply even with one run. Check method, phase-conductor layout, spacing and manufacturer data.
    Step 3 · Short-circuit withstand

    Fault clearing conditions

    Optional thermal screening. Enter the prospective fault current at the feeder and the protection clearing time (up to 5 seconds). Both are required for this check.

    Assume equal division across equivalent parallel paths.
    Step 4 · Verification results

    Preliminary cable checks

    Enter valid positive values. For the optional short-circuit check, enter both the fault current and the clearing time (up to 5 s), or leave both blank. Missing ampacity or breaker inputs are allowed and correctly shown as PENDING.

    Correction factors and installation assumptions: General cable sizing guide ↗. Full explanation: LV Cable Sizing Guide →