How Many 1/0 AWG THHN Fit in 1-1/2-Inch EMT?
4 conductors of 1/0 AWG THHN fit in 1-1/2-inch EMT at the NEC fill limit — 36.4% of the conduit's 2.036 in² interior.
4 conductors of 1/0 AWG THHN fit in a 1-1/2-inch EMT at the NEC fill limit. Maximum fill is 36.4%, under the 40% allowed for three or more conductors per NEC Chapter 9, Table 1.
The math
| Variable | Value | Source |
|---|---|---|
| 1/0 AWG THHN area | 0.1855 in² | NEC Table 5 |
| 1-1/2" EMT interior | 2.036 in² | NEC Table 4 |
| 40% allowance | 0.8144 in² | NEC Table 1 |
| Max conductors | floor(0.8144 / 0.1855) = 4 | calc |
Practical configurations
- 150A sub-panel feeder: 2 hots + 1 neutral + 1 EGC (sized per NEC 250.122) = 4 conductors → at the limit ✓
- 150A 240V dedicated load: 2 hots + 1 EGC = 3 conductors → 27.3% fill, lots of margin
- Parallel 1/0 phases for 300A service: 2 sets of phases + neutrals = 8+ conductors → won't fit, needs 2-1/2 EMT or larger
Next size up
- 2-inch EMT fits 7 of 1/0 THHN at 37.6% fill
- 2-1/2 EMT fits 12 at 38.0% fill
For real feeders (1/0 phase + smaller EGC), use the conduit fill calculator.
Ampacity
1/0 copper THHN: 170A at 90°C, 150A at 75°C, 125A at 60°C terminals. Standard breaker sizes: 150A, 175A. With 4 CCCs derate by 0.80: 170 × 0.80 = 136A — sufficient for 125A protection, marginal for 150A.
For 150A with derating, consider stepping to 2/0 (195A at 90°C × 0.80 = 156A).
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This page's figures are transcribed from NEC 2023 (NFPA 70) Chapter 9, Tables 1, 4 and 5, and checked by a version-controlled automated test suite — they are not signed off by a licensed professional. WireFillChart is an independent reference, not affiliated with or endorsed by NFPA. Always verify against the code edition adopted by your local authority having jurisdiction (AHJ).