Cable conductor resistance chart
The maximum DC resistance a class 2 stranded conductor may have at 20 °C, for copper and aluminium, with the values corrected to PVC (70 °C) and XLPE (90 °C) operating temperatures. Pick any size and temperature to calculate.
Basis
IEC 60228 / IS 8130, class 2 conductors; temperature coefficient 0.00393 /°C copper, 0.00403 /°C aluminium.
Reference values for planning and comparison. Confirm against the current standard, the purchaser’s specification and the manufacturer’s datasheet before ordering.
Conductor resistance chart (Ω/km, maximum DC)
| Size | Cu Ω/km 20 °C | Cu 70 °C | Cu 90 °C | Al Ω/km 20 °C | Al 90 °C |
|---|---|---|---|---|---|
| 1.5 mm² | 12.1 | 14.4776 | 15.4287 | — | — |
| 2.5 mm² | 7.41 | 8.8661 | 9.4485 | — | — |
| 4 mm² | 4.61 | 5.5159 | 5.8782 | — | — |
| 6 mm² | 3.08 | 3.6852 | 3.9273 | — | — |
| 10 mm² | 1.83 | 2.1896 | 2.3334 | 3.08 | 3.9489 |
| 16 mm² | 1.15 | 1.376 | 1.4664 | 1.91 | 2.4488 |
| 25 mm² | 0.727 | 0.8699 | 0.927 | 1.2 | 1.5385 |
| 35 mm² | 0.524 | 0.627 | 0.6682 | 0.868 | 1.1129 |
| 50 mm² | 0.387 | 0.463 | 0.4935 | 0.641 | 0.8218 |
| 70 mm² | 0.268 | 0.3207 | 0.3417 | 0.443 | 0.568 |
| 95 mm² | 0.193 | 0.2309 | 0.2461 | 0.32 | 0.4103 |
| 120 mm² | 0.153 | 0.1831 | 0.1951 | 0.253 | 0.3244 |
| 150 mm² | 0.124 | 0.1484 | 0.1581 | 0.206 | 0.2641 |
| 185 mm² | 0.0991 | 0.1186 | 0.1264 | 0.164 | 0.2103 |
| 240 mm² | 0.0754 | 0.0902 | 0.0961 | 0.125 | 0.1603 |
| 300 mm² | 0.0601 | 0.0719 | 0.0766 | 0.1 | 0.1282 |
| 400 mm² | 0.047 | 0.0562 | 0.0599 | 0.0778 | 0.0997 |
| 500 mm² | 0.0366 | 0.0438 | 0.0467 | 0.0605 | 0.0776 |
| 630 mm² | 0.0283 | 0.0339 | 0.0361 | 0.0469 | 0.0601 |
Worked example: 240 mm² aluminium at 90 °C
- R20 = 0.125 Ω/km (IEC 60228 maximum).
- R90 = 0.125 × (1 + 0.00403 × 70) = 0.1603 Ω/km.
- Over a 300 m run: 0.0481 Ω per conductor.
What is the resistance of 95 mm² copper cable?
0.193 Ω/km maximum DC at 20 °C (IEC 60228 class 2), about 0.246 Ω/km at 90 °C.
What is the resistance of 240 mm² aluminium cable?
0.125 Ω/km maximum DC at 20 °C, about 0.160 Ω/km at 90 °C.
Is AC resistance higher than DC resistance?
Yes, slightly, because of skin and proximity effects. The difference is small below about 150 mm² and grows for large conductors.