Reference · NEC 2023 Chapter 9 · THHN
Conduit fill chart — how many wires fit
Maximum THHN conductors per trade size at the 40% limit for three or more wires — EMT and PVC Schedule 40, computed from NEC Tables 4 and 5 with the same math as our calculator. Mixed sizes or XHHW? Run the calculator instead.
EMT — branch sizes (14–6 AWG THHN)
| Trade size | 14 | 12 | 10 | 8 | 6 |
|---|---|---|---|---|---|
| 1/2″ | 12 | 9 | 5 | 3 | 1 |
| 3/4″ | 21 | 16 | 10 | 5 | 4 |
| 1″ | 35 | 25 | 16 | 9 | 6 |
| 1-1/4″ | 61 | 44 | 28 | 16 | 11 |
| 1-1/2″ | 83 | 61 | 38 | 22 | 16 |
| 2″ | 138 | 100 | 63 | 36 | 26 |
EMT — feeder sizes (4 AWG–4/0 THHN)
| Trade size | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|
| 1/2″ | 1 | 1 | 1 | 1 | — | — | — | — |
| 3/4″ | 2 | 1 | 1 | 1 | 1 | 1 | 1 | — |
| 1″ | 4 | 3 | 2 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4″ | 7 | 6 | 5 | 3 | 3 | 2 | 1 | 1 |
| 1-1/2″ | 9 | 8 | 7 | 5 | 4 | 3 | 3 | 1 |
| 2″ | 16 | 13 | 11 | 8 | 7 | 6 | 5 | 4 |
PVC Schedule 40 — branch sizes (14–6 AWG THHN)
| Trade size | 14 | 12 | 10 | 8 | 6 |
|---|---|---|---|---|---|
| 1/2″ | 11 | 8 | 5 | 3 | 1 |
| 3/4″ | 20 | 15 | 9 | 5 | 4 |
| 1″ | 34 | 25 | 15 | 9 | 6 |
| 1-1/4″ | 59 | 43 | 27 | 15 | 11 |
| 1-1/2″ | 81 | 59 | 37 | 21 | 15 |
| 2″ | 135 | 98 | 62 | 35 | 25 |
PVC Schedule 40 — feeder sizes (4 AWG–4/0 THHN)
| Trade size | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|
| 1/2″ | 1 | 1 | 1 | — | — | — | — | — |
| 3/4″ | 1 | 1 | 1 | 1 | 1 | 1 | 1 | — |
| 1″ | 4 | 3 | 2 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4″ | 7 | 5 | 5 | 3 | 3 | 2 | 1 | 1 |
| 1-1/2″ | 9 | 8 | 6 | 5 | 4 | 3 | 2 | 1 |
| 2″ | 15 | 13 | 11 | 8 | 7 | 5 | 4 | 4 |
The pulls you'll actually run
3/4″ EMT with #12 THHN → 16
0.533 in² × 40% = 0.213 in² ÷ 0.0133 per wire. The classic residential branch-circuit pull — four circuits with grounds still leave headroom.
1/2″ EMT with #12 THHN → 9
0.304 in² × 40% = 0.122 in² ÷ 0.0133. Half-inch runs out fast past #10 — three #8 is the practical ceiling.
1″ EMT service with #4/0 → 1 alone, 4 in 2″
One 4/0 needs 1″ minimum; a 200A pull of three 4/0 plus neutral lands at 2″ once every conductor is counted.
Only one #6 in 1/2″ — not two
Two conductors are held to 31%, not 40%. Two #6 in 1/2″ EMT hits ~33% and fails — the rule that catches everyone once.
Rules this chart assumes
Uniform THHN only
Every conductor the same AWG and THHN insulation. Mixed sizes, XHHW, or cable assemblies change the area math — use the calculator.
Ground counts for fill
Neutrals and equipment grounds each take a slot. A 4-wire circuit with ground is 5 conductors against this chart.
Nipples get 60%
Conduit 24″ or less between enclosures may fill to 60% per Note 4 — and skips bundling derating. Long runs stay at 40%.
Fill ≠ ampacity
A pull can pass fill and still fail derating: 4–6 conductors ×0.80, 7–9 ×0.70, 10–20 ×0.50. Check both with the wire size calculator.
Note: NEC Annex C prints one wire more in a few cells (e.g. 22× #14, 6× #8 in 3/4″ EMT) via Note 7 rounding. This chart uses strict Table 4 × Table 5 area math — identical to our calculator — so borderline cells read one conservative. When they disagree, follow your AHJ.
Conduit fill questions, answered
How many #12 THHN in 3/4″ EMT?
Sixteen — about 40% fill, the maximum for three or more conductors. Same raceway: twenty-one #14, ten #10, five #8.
How many wires in 1/2″ conduit?
EMT: twelve #14, nine #12, five #10, three #8. PVC Sch 40: eleven, eight, five, three — thicker walls cost one wire.
Does the ground count?
Yes for fill (Note 3), no for derating. The ground takes space but makes no heat — two rules, two answers.
What is the 40% rule?
Table 1: 1 wire 53% · 2 wires 31% · 3+ wires 40% of total internal area. Nipples ≤24″ get 60%.
What about mixed sizes?
Sum every Table 5 area ÷ Table 4 area, compare to the Table 1 limit for your count. The calculator does this in one tap.
Fill passed — am I done?
No. Check bundling derating (310.15) and voltage drop separately. A packed conduit often needs larger wire, not larger pipe.
Does PVC use the same 40% limit?
Yes — 53/31/40% applies to every raceway. PVC Sch 40 just has less room: fifteen #12 in 3/4″ PVC vs sixteen in EMT.