How Many 4 AWG THHN Fit in 1-Inch EMT?
4 conductors of 4 AWG THHN fit in 1-inch EMT at the NEC fill limit — 38.1% of the conduit's 0.864 in² interior.
4 conductors of 4 AWG THHN fit in a 1-inch EMT at the NEC fill limit. Maximum fill is 38.1%, just under the 40% allowed for three or more conductors per NEC Chapter 9, Table 1.
The math
| Variable | Value | Source |
|---|---|---|
| 4 AWG THHN area | 0.0824 in² | NEC Table 5 |
| 1" EMT interior | 0.864 in² | NEC Table 4 |
| 40% allowance | 0.3456 in² | NEC Table 1 |
| Max conductors | floor(0.3456 / 0.0824) = 4 | calc |
Practical configurations
- Small sub-panel feeder, 70A: 2 hots + 1 neutral + 1 EGC = 4 conductors → at the limit ✓
- Two 3-wire 240V branches sharing EGC: 4 hots + 1 neutral + 1 EGC = 6 conductors → won't fit, needs 1-1/4
Next size up
- 1-1/4 EMT fits 7 of 4 AWG THHN at 38.6% fill
- 1-1/2 EMT fits 9 at 36.4% fill
For mixed feeders (4 AWG phase + 8 AWG EGC per NEC 250.122), check the actual mix in the conduit fill calculator.
Ampacity
4 AWG THHN: 95A at 90°C, 85A at 75°C, 70A at 60°C terminals. Common breaker sizes: 70A, 80A, 90A. With 4 CCCs derate by 0.80: 95 × 0.80 = 76A — sufficient for 70A protection.
For copper feeders sized to 100A, jump to 3 AWG (0.0973 in² — fits 3 in 1" EMT at 33.8% fill).
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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).