10 mm² copper is rated about 64 A installed per Method C (clipped direct, 70 °C thermoplastic) and drops 4.5 mV/A/m (single-phase figure, matching BS 7671 Appendix 4 within rounding). The chart shows how far it runs before the drop exceeds the limits.
| Load | 230 V @ 3% | 230 V @ 5% | 400 V 3Ø @ 5% |
|---|---|---|---|
| 6 A | 256 m | 426 m | 855 m |
| 10 A | 153 m | 256 m | 513 m |
| 16 A | 96 m | 160 m | 321 m |
| 20 A | 77 m | 128 m | 257 m |
| 32 A | 48 m | 80 m | 160 m |
| 40 A | 38 m | 64 m | 128 m |
| 63 A | 24 m | 41 m | 81 m |
Computed with ρ ≈ 0.0225 Ω·mm²/m (copper at operating temperature), matching BS 7671 Appendix 4 mV/A/m values within rounding. Grouping, insulation type and installation method change the amp rating — treat 64 A as the Method C reference figure.
The nearest equal-or-larger AWG size is 6 AWG — see the gauge converter for exact areas.
About 64 A for copper clipped direct (Method C). Enclosed in conduit in insulation it derates substantially — always check the installation method column in BS 7671 Appendix 4.