What Size Cable Do You Need for a 50 Amp Circuit?
For a 50 amp circuit, use 10mm² copper cable under BS 7671 Table 4D5A, rated at 57A clipped direct. Under NEC, 6 AWG at 75°C is rated for 65A per Table 310.16. This size is common for sub-main feeds to outbuilding distribution boards and large workshop supplies.
Quick Reference: Cable Size for 50 Amp Sub-Main Circuit by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 10mm² | Method C (clipped direct), PVC insulation | Table 4D5A |
| NEC | 6 AWG | 50A circuit, THWN-2, 75°C column | Table 310.16 |
| AS/NZS 3008 | 10mm² | Clipped direct, max 30°C ambient | Table 13 |
| IEC 60364 | 10mm² | Reference method C, PVC insulation | Table B.52.4 |
Values shown are for copper conductors in typical domestic/commercial conditions. Actual size depends on installation method, ambient temperature, and cable length. Use our free cable sizing calculator for your exact scenario.
Typical Applications for a 50 Amp Sub-Main Circuit
- Sub-main distribution
- Large appliance feed
- Workshop main supply
- Commercial kitchen feed
Calculate Your Exact Cable Size
These are general guidelines. Your specific installation needs exact calculation accounting for cable route length, installation method, ambient temperature, and cable grouping.
Frequently Asked Questions
Is 10mm² enough for 50 amps?▼
Yes. 10mm² PVC copper cable clipped direct is rated at 57A under BS 7671, providing adequate margin. In conduit (Method B) the rating drops to 48A — in that case, use 16mm² for 50A circuits installed in conduit.
Can I use 6mm² for a 50 amp circuit?▼
No. 6mm² cable is rated at only 47A clipped direct — insufficient for a 50A circuit. The minimum size is 10mm² for PVC insulation. With XLPE insulation, 6mm² is rated at 57A which is technically sufficient.
What is 6 AWG in mm²?▼
6 AWG has a cross-sectional area of 13.3mm², which falls between 10mm² and 16mm² in metric sizing. Its NEC ampacity at 75°C is 65A per Table 310.16, comfortably above 50A.
What size SWA cable for a 50 amp sub-main?▼
Use 10mm² 3-core SWA for a single-phase 50A sub-main, or 16mm² if the run exceeds 30m. For three-phase, 10mm² 4-core SWA is appropriate for most run lengths.
How far can I run 10mm² at 50 amps?▼
At 230V with a 5% voltage drop limit, 10mm² cable can run approximately 16m at 50A. For 16mm², the maximum extends to about 26m. Longer sub-main runs may require 25mm² to keep within voltage drop limits.
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