Cable Sizing Calculator
An online calculator for determining the minimum permissible cable cross-section based on continuous current-carrying capacity. Takes into account conductor material (copper/aluminum), installation method (in air, in ground, in conduit), number of loaded cores, and ambient temperature.
Calculations follow IEC 60364-5-52 ampacity tables and GOST R 50571.5-52. The calculator automatically applies derating factors for grouping and elevated ambient temperature.
Features
- Minimum cross-section calculation by continuous current rating
- Installation method support: in air, underground, in conduit, in trunking
- Material selection: copper (Cu) and aluminum (Al)
- Automatic selection of nearest standard cross-section
- Compliance check against IEC and GOST requirements
- Derating factor calculation (temperature, grouping)
Standards
- IEC 60364-5-52 — Low-voltage electrical installations, current-carrying capacities
- GOST R 50571.5-52 — Russian national standard for LV installations
- IS 732 (India) — Code of practice for electrical wiring installations
Frequently asked questions
How many amps can 2.5 mm² cable carry?
Copper 2.5 mm² in conduit carries up to 25 A (IEC 60364-5-52), in free air up to 30 A. For a 16 A breaker 2.5 mm² is sufficient.
Why size cable by power, not length?
Load current comes from power: I = P/(U·cosφ). Length affects voltage drop, not heating — use the voltage-drop calculator for long runs.
Should I account for cable length?
Yes — for runs over 25–30 m check the voltage drop (max 5%, 2.5% for lighting). Increase the cross-section if exceeded.
Which cable for 3.5 kW?
At 230 V the current is ≈ 15 A — 1.5 mm² would suffice, but sockets require a minimum of 2.5 mm² (NEC 210 / IEC). Use 2.5 mm².