How Many 10 AWG THHN Fit in 3/4-Inch EMT?
10 conductors of 10 AWG THHN fit in 3/4-inch EMT at the NEC 40% fill limit — 39.6% of the conduit's 0.533 in² interior.
10 conductors of 10 AWG THHN fit in a 3/4-inch EMT at the NEC fill limit. At the maximum count, fill is 39.6% — just under the 40% allowed for three or more conductors per NEC Chapter 9, Table 1.
The math
| Variable | Value | Source |
|---|---|---|
| Conductor area (10 AWG THHN) | 0.0211 in² | NEC 2023 Ch. 9 Table 5 |
| Conduit interior (3/4" EMT) | 0.533 in² | NEC 2023 Ch. 9 Table 4 |
| Allowed fill (3+ conductors) | 40% | NEC 2023 Ch. 9 Table 1 |
Allowable conductor area: 0.533 × 0.40 = 0.2132 in²
Maximum conductors: 0.2132 ÷ 0.0211 = 10.10 → floor 10 conductors.
Common 10 AWG THHN applications
10 AWG is the workhorse of 30-amp branch circuits. Typical applications:
- Electric water heater (30A 240V): 2 hots + 1 EGC = 3 conductors
- Electric clothes dryer (30A 240V): 2 hots + 1 neutral + 1 EGC = 4 conductors
- Baseboard heat (30A): 2 hots + 1 EGC = 3 conductors
- Mini-split heat pump (30A 240V): 2 hots + 1 EGC = 3 conductors
- EV charger (30A): 2 hots + 1 EGC = 3 conductors
You can fit three 30-amp dryers (12 conductors) in a 3/4-inch EMT? No — 12 conductors of 10 AWG = 47% fill, over the limit. Two dryers (8 conductors) fits at 31.7%.
Ampacity adjustment
10 AWG THHN has a 90°C ampacity of 40A. The 60°C terminal rating limits it to 30A — the practical NEC 240.4(D) cap for 10 AWG.
With 4–6 CCCs in the raceway, apply 0.80 derate to the 90°C value: 40 × 0.80 = 32A. Still ≥ 30A breaker rating — compliant.
Push to 7–9 CCCs: 40 × 0.70 = 28A. Now you've dropped below the 30A breaker rating — derate makes the 10 AWG insufficient. Either reduce the count, run more conduit, or upsize to 8 AWG.
What if I need more than 10?
Next sizes up for 10 AWG THHN:
- 1-inch EMT: fits 16 at 39.0% fill
- 1-1/4 EMT: fits 28 at 39.5% fill
For mixed-gauge runs (say 4 × 10 AWG + 2 × 6 AWG), use the conduit fill calculator.
Other insulations at 10 AWG
- THHN / THWN-2 / XHHW / XHHW-2: 0.0211 in² → 10 fit in 3/4" EMT
- RHH / RHW / RHW-2: 0.0333 in² → 6 fit in 3/4" EMT
- TW: 0.0243 in² → 8 fit in 3/4" EMT
Where to verify your specific job
The numbers above assume identical conductors. Real jobs often mix:
- Phase conductors at one gauge, neutral at another
- EGC upsized for parallel runs (NEC 250.122 / 250.166)
- Multiple insulation types (THHN switchleg + RHW feeder)
Plug your exact conductor list into the conduit fill calculator — it accepts up to 10 conductor rows and reports fill %, NEC status, jam probability, and the next-size-up conduit if you're over.
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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).