Electrical Cable Sizing Calculator
Evaluate your cable cross-section considering both voltage drop and current carrying capacity (ampacity). Perform pre-sizing for copper and aluminum conductors, and send the results to ONX Control engineers to receive proper product and application support.
Electrical Inputs
Basic CalculationConductor and Installation
Thermal ConditionsDetailed Results
Live AnalysisStandard Size Reference
mm² + AWG| mm² | Approx. AWG/kcmil | Usage Note |
|---|---|---|
| 2.5 | ≈ 13 AWG | Control and small loads |
| 6 | ≈ 9 AWG | Medium current applications |
| 16 | ≈ 5 AWG | Machine supplies |
| 35 | ≈ 2 AWG | Higher current and longer runs |
| 95 | ≈ 3/0 AWG | High-power industrial feeds |
| 240 | ≈ 500 kcmil | Main distribution and high current |
These mappings are approximate references for practical comparison. The final selection must be verified according to the mm² cross-section and relevant standards.
Engineering Expert Window
Voltage drop can be critical: Especially in long runs or low voltage systems, even if the ampacity seems sufficient, voltage drop might necessitate a larger cross-section.
Thermal conditions alter results: As installation type, ambient temperature, and the number of loaded conductors increase, the allowed ampacity drops. Therefore, looking solely at current is often not enough.
How to Calculate Electrical Cable Size?
When selecting a cable cross-section, two main criteria must be evaluated together: current carrying capacity (ampacity) and allowable voltage drop. If the cable is undersized, heating, efficiency loss, and voltage drop will increase; if oversized, costs will rise unnecessarily.
The calculator on this page performs pre-sizing based on conductor material, phase type, line length, ambient temperature, number of loaded conductors, and installation type. It displays both the minimum size dictated by voltage drop and the minimum size dictated by ampacity separately.
Prepared by ONX Control, this tool is ideal for making quick preliminary decisions, especially for machine feeds, motor supplies, panel outputs, and long cable runs. In the final project, relevant IEC/local standards, manufacturer tables, short-circuit withstand, and protection device selection must be further verified.
Frequently Asked Questions
Why is voltage drop important?
As cable length increases, voltage loss occurs along the line. If this loss is excessive, motors may struggle to start, equipment performance can degrade, and overheating may occur.
What is the difference between copper and aluminum cables?
An aluminum conductor generally requires a larger cross-section for the same current. However, it can offer advantages in terms of cost and weight in certain applications.
Which is more decisive: ampacity or voltage drop?
For short distances, ampacity is usually the determining factor. For long distances, voltage drop almost always dictates a larger cable size.
Is this result sufficient for the final project?
No. This tool is for pre-sizing. In the final project, short-circuit withstand, protection device coordination, grounding, and relevant standard verification must also be performed.
ONX Technical Summary
Live cable sizing result