FIG. 01 — DIRECT ANSWER
How Many #10 THHN Fit in 1-1/4" EMT?
Maximum #10 THHN conductor count for 1-1/4" EMT at the NEC 2023 40% fill cap (3 or more conductors).
FIG. 02
THE MATH IN ONE PASS
CONDUIT
1-1/4" EMT (Article 358)
A = 1.4960 in²
NEC Ch.9 Table 4 — 100% interior area
40% allowable = 0.5984 in²
CONDUCTOR
#10 THHN
A₁ = 0.0211 in²
NEC Ch.9 Table 5 — single-conductor cross-section
0.5984 ÷ 0.0211 = 28 max
FIG. 03
STEP UP OR STEP DOWN A SIZE
| Trade size | Area (in²) | 40% allowed (in²) | Max #10 THHN |
|---|---|---|---|
| 1" EMT (smaller) | 0.8640 | 0.3456 | 16 |
| 1-1/4" EMT ← | 1.4960 | 0.5984 | 28 |
| 1-1/2" EMT (larger) | 2.0360 | 0.8144 | 38 |
All values per NEC 2023 · Chapter 9 · Tables 1, 4 and 5. THHN/THWN-2/XHHW share identical conductor area.
FIG. 04
FREQUENTLY ASKED QUESTIONS
28 conductors, applying the NEC 2023 40% fill rule for 3+ conductors. The conduit's interior area is 1.4960 in² and the allowable conductor area is 0.5984 in² (NEC Ch.9 Table 4, Article 358).