DOC · ARTICLE
How Many 4/0 AWG THHN Fit in 2-Inch EMT?
4 conductors of 4/0 AWG THHN fit in 2-inch EMT at the NEC fill limit — 38.6% of the conduit's 3.356 in² interior.
·1 MIN READ·EDITORIAL
4 conductors of 4/0 AWG THHN fit in a 2-inch EMT at the NEC fill limit. Maximum fill is 38.6%, under the 40% allowed for three or more conductors per NEC Chapter 9, Table 1.
The math
| Variable | Value | Source |
|---|---|---|
| 4/0 AWG THHN area | 0.3237 in² | NEC Table 5 |
| 2" EMT interior | 3.356 in² | NEC Table 4 |
| 40% allowance | 1.3424 in² | NEC Table 1 |
| Max conductors | floor(1.3424 / 0.3237) = 4 | calc |
Practical configurations
- 200A service entrance (copper 4/0): 2 hots + 1 neutral = 3 conductors → 28.9% fill ✓
- 200A service with EGC pulled through (uncommon — usually GEC is separate): 4 conductors → at limit
- 400A parallel service via 4/0: 2 sets × 3 = 6 conductors of 4/0 → exceeds 40%, needs 3-inch RMC or larger
Next size up
- 2-1/2 EMT fits 6 of 4/0 THHN at 33.2% fill
- 3-inch EMT fits 10 at 36.2% fill
For the typical 200A residential install with mixed gauges (4/0 phase + 4 AWG EGC), use the conduit fill calculator.
Ampacity
4/0 copper THHN: 260A at 90°C, 230A at 75°C, 195A at 60°C terminals. With 4 CCCs derate by 0.80: 260 × 0.80 = 208A — sufficient for 200A protection.
For 4/0 aluminum (more common at this size): 205A at 90°C × 0.80 = 164A — derating drops below 200A. Most 200A aluminum services use 250 kcmil or 300 kcmil aluminum to clear the derate margin.
FIG. 99
FAQ
4 conductors of 4/0 AWG THHN fit in 2-inch EMT at the NEC 40% fill limit. Calculation: 4 × 0.3237 in² = 1.2948 in², or 38.58% of EMT's 3.356 in² interior.
FIG. 98