BS7671:2018+A2 · Appendix 4BS7671 Cable Current Rating Tables
Tabulated current-carrying capacities for PVC and XLPE copper cables, plus the ambient temperature and grouping correction factors, straight from BS7671:2018 Amendment 2 Appendix 4.
Every cable size shown by this calculator traces back to one of these tables. The tabulated rating It is the maximum current a cable can carry continuously at a 30°C ambient, installed alone, with no thermal insulation contact. Real installations rarely match those exact conditions, so It gets corrected down (or occasionally up) before it can be compared against a protective device rating — see the correction factors section below.
Table 4D1A — Multicore PVC, 70°C, copper
2 or 3 loaded conductors, e.g. twin-and-earth, PVC/PVC multicore, PVC/SWA/PVC — current-carrying capacity in amps| CSA mm² | A1 | A2 | B1 | B2 | C |
|---|
| 1 | 11 | 10.5 | 13 | 12.5 | 15 |
| 1.5 | 14.5 | 13.5 | 16.5 | 15.5 | 19.5 |
| 2.5 | 19.5 | 18.5 | 23 | 21 | 27 |
| 4 | 26 | 25 | 30 | 28 | 36 |
| 6 | 34 | 32 | 38 | 35 | 46 |
| 10 | 46 | 43 | 52 | 48 | 63 |
| 16 | 61 | 57 | 69 | 64 | 85 |
| 25 | 80 | 75 | 90 | 84 | 110 |
| 35 | 99 | 92 | 111 | 103 | 133 |
| 50 | 119 | 110 | 133 | 124 | 159 |
| 70 | 151 | 139 | 168 | 156 | 200 |
| 95 | 182 | 167 | 201 | 188 | 241 |
| 120 | 210 | 192 | 232 | 216 | 278 |
| 150 | 240 | 219 | 258 | 245 | 318 |
| 185 | 273 | 248 | 294 | 278 | 362 |
| 240 | 321 | 291 | 344 | 325 | 424 |
| 300 | 367 | 334 | 394 | 371 | 486 |
Table 4D2A — Single-core PVC, 70°C, copper
In free air, reference methods E and F — current-carrying capacity in amps| CSA mm² | E | F |
|---|
| 1 | 15 | 15 |
| 1.5 | 19.5 | 19.5 |
| 2.5 | 27 | 27 |
| 4 | 36 | 36 |
| 6 | 46 | 46 |
| 10 | 63 | 63 |
| 16 | 85 | 85 |
| 25 | 110 | 114 |
| 35 | 133 | 141 |
| 50 | 159 | 170 |
| 70 | 200 | 213 |
| 95 | 241 | 256 |
| 120 | 278 | 293 |
| 150 | 318 | 336 |
| 185 | 362 | 383 |
| 240 | 424 | 449 |
| 300 | 486 | 515 |
| 400 | 561 | 600 |
Table 4E1A — Multicore XLPE, 90°C, copper
2 or 3 loaded conductors, e.g. XLPE/SWA/PVC, XLPE/LSZH — current-carrying capacity in amps| CSA mm² | A1 | A2 | B1 | B2 | C |
|---|
| 1 | 13 | 12.5 | 15 | 14.5 | 17.5 |
| 1.5 | 17 | 16 | 19.5 | 18.5 | 23 |
| 2.5 | 23 | 22 | 27 | 25 | 31 |
| 4 | 31 | 30 | 36 | 34 | 42 |
| 6 | 40 | 38 | 46 | 43 | 54 |
| 10 | 54 | 51 | 63 | 59 | 73 |
| 16 | 73 | 68 | 85 | 79 | 98 |
| 25 | 95 | 89 | 112 | 104 | 129 |
| 35 | 117 | 110 | 138 | 129 | 158 |
| 50 | 141 | 132 | 168 | 154 | 191 |
| 70 | 179 | 167 | 213 | 194 | 246 |
| 95 | 216 | 202 | 258 | 233 | 298 |
| 120 | 249 | 233 | 299 | 268 | 346 |
| 150 | 285 | 265 | 344 | 300 | 395 |
| 185 | 324 | 300 | 392 | 341 | 450 |
| 240 | 380 | 351 | 461 | 400 | 530 |
| 300 | 435 | 402 | 530 | 460 | 610 |
Table 4E2A — Single-core XLPE, 90°C, copper
In free air, reference methods E and F — current-carrying capacity in amps| CSA mm² | E | F |
|---|
| 1 | 17.5 | 17.5 |
| 1.5 | 23 | 23 |
| 2.5 | 31 | 31 |
| 4 | 42 | 42 |
| 6 | 54 | 54 |
| 10 | 73 | 73 |
| 16 | 98 | 98 |
| 25 | 129 | 134 |
| 35 | 158 | 167 |
| 50 | 191 | 201 |
| 70 | 246 | 261 |
| 95 | 298 | 315 |
| 120 | 346 | 364 |
| 150 | 395 | 416 |
| 185 | 450 | 473 |
| 240 | 530 | 558 |
| 300 | 610 | 642 |
| 400 | 718 | 754 |
Correction factors
Apply the relevant factors to the tabulated rating: Iz = It × Ca × Cg × Ci × Cc. A cable is compliant when Iz is at least equal to the protective device rating In, and In is at least equal to the design current Ib.
Table 4B1 — Ambient temperature factor Ca
Correction applied when ambient temperature differs from the 30°C the tables assume| Ambient °C | PVC (70°C) | XLPE (90°C) |
|---|
| 10 | 1.22 | 1.15 |
| 15 | 1.17 | 1.12 |
| 20 | 1.12 | 1.08 |
| 25 | 1.06 | 1.04 |
| 30 | 1 | 1 |
| 35 | 0.94 | 0.96 |
| 40 | 0.87 | 0.91 |
| 45 | 0.79 | 0.87 |
| 50 | 0.71 | 0.82 |
| 55 | 0.61 | 0.76 |
| 60 | 0.5 | 0.71 |
| 65 | 0.35 | 0.65 |
| 70 | — | 0.58 |
| 75 | — | 0.5 |
| 80 | — | 0.41 |
| 85 | — | 0.29 |
Table 4C1 — Grouping factor Cg
Correction applied when multiple circuits are grouped together (bunched, in a duct, or on a tray)| Circuits in group | Cg |
|---|
| 1 | 1.00 |
| 2 | 0.80 |
| 3 | 0.70 |
| 4 | 0.65 |
| 5 | 0.60 |
| 6 | 0.57 |
| 7 | 0.54 |
| 8 | 0.52 |
| 9 | 0.50 |
| 10 | 0.48 |
| 12 | 0.45 |
| 14 | 0.43 |
| 16 | 0.41 |
| 20 | 0.38 |
Two further factors apply but aren't published as simple lookup tables here: Ci (thermal insulation contact — 1.00 with none, 0.75 touching on one side, 0.50 fully surrounded, per Regulation 523.9 / Table 52.2) and Cc (protective device — 1.00 for MCBs, MCCBs and RCDs, 0.725 for BS3036 semi-enclosed fuses).