PRELIMINARY ENGINEERING TOOL
Preliminary cable-size calculator
Evaluate custom cable data in ascending size order. Production automatic cable tables are intentionally not included.
Inputs
| Size | Corrected Iz | Voltage drop | Status |
|---|---|---|---|
| 2.5 mm² | 17.28 A | 4.2% | ampacity, voltage drop |
| 4 mm² | 23.04 A | 2.7% | ampacity |
| 6 mm² | 29.52 A | 1.8% | Pass |
| 10 mm² | 41.04 A | 1.1% | Pass |
Calculation steps
It = Ib / Ctotal = 25 / 0.720 = 34.72 A
Iz = Iz(table) × Ctotal. Formula ID: CABLE_SELECT_CUSTOM_V1
Assumptions and references
Preliminary calculation only. Verify inputs, manufacturer data, applicable standards, fault levels, and local requirements before construction or procurement.
UNDERSTAND THE TOOL
What this calculator does
This tool sorts the cable candidates you supply and shows each candidate’s pass or fail state. It deliberately uses custom or demo data and labels results Review required; it does not embed licensed standards tables or make a compliance decision.
How to use it
- Enter design current and your selected voltage-drop target.
- Add or import traceable cable, ampacity and correction-factor data.
- Check the composed correction factor and each candidate’s corrected ampacity and drop result.
- Select only a candidate that has been independently reviewed for the installation and governing requirements.
Fields and meanings
- Design current (Ib)
- Expected load current used for the preliminary assessment.
- Base ampacity
- A value from your own traceable cable dataset.
- Correction factors
- User-supplied factors applied to base ampacity.
- Cable data
- Resistance, reactance or mV/A/m values used for voltage-drop checking.
- Thermal short-circuit check
- Optional and only usable with appropriate verified input data.
Review required. A passing custom-data check is not approval, certification or a construction instruction.
Read the full cable assessment article →