thousand circular mils
Areaexact by definition
A kcmil is one thousand circular mils, about 5.067 × 10⁻⁷ m² or 0.5067 mm². It is the standard size designation for large electrical conductors in North America, taking over where American Wire Gauge runs out above 4/0: a 500 kcmil feeder is a common service conductor.
Watch out: A kcmil is a conductor cross section, not an ampacity. Two 500 kcmil cables in different insulations, temperatures and conduit fills carry very different currents, and the NEC tables exist precisely because the area alone does not answer the question.
| 1 kcmil | 5.0670748e-07 m² |
The older designation was MCM, using the Roman numeral M for a thousand. It means exactly the same thing, and the NEC switched to kcmil to stop people reading the M as the SI mega prefix. Both appear on cable reels.