What Size Cable Do You Need for a 63 Amp Circuit?
For a 63 amp circuit, use 16mm² copper cable (BS 7671, IEC, AS/NZS) or 6 AWG (NEC). This is typical for sub-main distribution boards and three-phase motor feeds. XLPE insulation allows smaller sizes — 10mm² XLPE is rated at 68A clipped direct.
Quick Reference: Cable Size for 63 Amp Circuit by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 16mm² | Method C or E, PVC or XLPE | Table 4D1A/4E1A |
| NEC | 6 AWG or 4 AWG | THWN-2, 75°C column | Table 310.16 |
| AS/NZS 3008 | 16mm² | Clipped direct or in tray | Table 13/14 |
| IEC 60364 | 16mm² | Reference method C or E | Table B.52.4/B.52.6 |
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 63 Amp Circuit
- Sub-main distribution
- Large commercial load
- Three-phase motor feed
- EV fast charger
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
Can I use 10mm² for 63 amps?▼
Only with XLPE (90°C) insulation clipped direct (Method C), which gives 68A — just above 63A. PVC 10mm² is rated at only 57A, which is insufficient. Always check derating factors.
What size SWA cable for 63 amps?▼
For steel wire armoured (SWA) cable at 63A, use 16mm² PVC/SWA or 10mm² XLPE/SWA. SWA is common for underground and external runs where mechanical protection is needed.
What size cable for a three-phase 63 amp supply?▼
For three-phase 63A, use 16mm² 4-core SWA cable (PVC) or 10mm² 4-core XLPE. The three-phase rating per conductor is slightly lower than single-phase due to mutual heating.
How much does 16mm² cable cost per metre?▼
16mm² twin and earth costs approximately £4-6 per metre, while 16mm² 4-core SWA costs £8-12 per metre. Prices vary by supplier and market conditions.
What size earth conductor for a 63 amp circuit?▼
Under BS 7671 Table 54.7, the minimum CPC for a 16mm² phase conductor is 16mm². If the CPC is a separate conductor (not in the cable), it may need to be 10mm² minimum depending on the adiabatic calculation.
Related Cable Sizing Guides
Need a different calculation?
Browse all 27 free calculators →