The question of which is bigger – 4/0 AWG wire vs 250 MCM wire – is quite an obvious one. In the US, we have two types of wires: smaller AWG wires and bigger MCM (or kcmil) wires. Here is where the dilemma comes from:
- 4/0 AWG is the biggest wire gauge among the smaller wires (AWG wires).
- 250 MCM is the smallest wire gauge among the bigger wires (MCM or kcmil wires).
Note: 4/0 AWG wire can also be denoted as 0000 AWG wire. 250 MCM wire can also be denoted as 250 kcmil wire; these are exactly the same wires.
To fully and easily answer the question of what is bigger 4/0 AWG or 250 MCM wire, let’s compare the specs of both of these wires:
4/0 AWG VS 250 MCM Wire Specifications
Here we can easily see which wire is bigger:
| Specification: | 4/0 AWG Wire: | 250 MCM Wire: |
| Diameter (mm): | 11.68 mm | 12.70 mm |
| Cross-section (mm2): | 107 mm2 | 126.7 mm2 |
| Ampacity At (75°C (167°F)): | 230 Amps | 255 Amps |
| Max. Allowable Amps (80% NEC Rule): | 184 Amps | 204 Amps |
As you can see, 250 MCM wire is bigger than 4/0 AWG wire.
250 MCM wire has:
- 8.7% bigger diameter than 4/0 AWG wire.
- 18.4% bigger cross-section than 4/0 AWG wire.
- 10.9% higher ampacity than 4/0 AWG wire.
- 10.9% higher maximal allowable amps than 4/0 AWG wire.
All in all, the 250 MCM can carry about 20 amps more than 0000 AWG wire. It is definitely the bigger wire. In fact, all MCM wires are bigger than the AWG wires. Hope this helps.