How Many 8 AWG THHN Fit in 3/4-Inch EMT?
5 conductors of 8 AWG THHN fit in 3/4-inch EMT at the NEC fill limit — 34.3% of the conduit's 0.533 in² interior.
5 conductors of 8 AWG THHN fit in a 3/4-inch EMT at the NEC fill limit. Maximum fill is 34.3%, well under the 40% allowed for three or more conductors per NEC Chapter 9, Table 1.
The math
| Variable | Value | Source |
|---|---|---|
| 8 AWG THHN area | 0.0366 in² | NEC Table 5 |
| 3/4" EMT interior | 0.533 in² | NEC Table 4 |
| 40% fill allowance | 0.2132 in² | NEC Table 1 |
| Max conductors | floor(0.2132 / 0.0366) = 5 | calc |
Practical configurations
- One 40A 240V circuit (range, dryer, EV): 2 hots + 1 EGC = 3 conductors → fits with margin
- One 40A 240V with neutral (range with neutral): 2 hots + 1 neutral + 1 EGC = 4 conductors → fits
- Two 40A circuits sharing EGC: 4 hots + 1 EGC = 5 conductors → at the limit
Next size up
- 1-inch EMT fits 9 of 8 AWG THHN (32.9% fill)
- 1-1/4 EMT fits 16 at 33.7% fill
Use the conduit fill calculator for mixed-gauge runs (typical: 8 AWG phase + 10 AWG EGC).
Ampacity adjustment
8 AWG THHN: 55A at 90°C, 50A at 75°C, 40A at 60°C terminals. With 4 CCCs in the raceway, derate by 0.80: 55 × 0.80 = 44A. Still acceptable for a 40A breaker.
Push to 5 CCCs and 6 CCCs and the math tightens — verify with the wire ampacity calculator.
Insulation alternatives
- THHN / THWN-2 / XHHW: 0.0366 in² → 5 fit
- RHH / RHW-2: 0.0556 in² → 3 fit
- TW: 0.0437 in² → 4 fit
FAQ
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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).