4" EMT Conduit Fill: How Many Wires Fit?
Verified against NEC 2023, checked against the 2026 edition · Last checked August 19, 2026
4" EMT holds 443 × 12 AWG, 279 × 10 AWG or 161 × 8 AWG THHN conductors at the 40% fill of Chapter 9 Table 1. A nipple not over 24 inches may be filled to 60% · Chapter 9 Notes, Note 4. Counts assume all conductors are the same size and insulation.
| Wire size | Max conductors | In a nipple (60%) |
|---|---|---|
| 14 AWG | 608 | 912 |
| 12 AWG | 443 | 665 |
| 10 AWG | 279 | 419 |
| 8 AWG | 161 | 242 |
| 6 AWG | 116 | 174 |
| 4 AWG | 71 | 107 |
| 3 AWG | 60 | 91 |
| 2 AWG | 51 | 76 |
| 1 AWG | 37 | 56 |
| 1/0 AWG | 32 | 47 |
| 2/0 AWG | 26 | 40 |
| 3/0 AWG | 22 | 33 |
| 4/0 AWG | 18 | 27 |
| 250 kcmil | 15 | 22 |
| 300 kcmil | 13 | 19 |
| 350 kcmil | 11 | 17 |
| 400 kcmil | 10 | 15 |
| 500 kcmil | 8 | 12 |
Counts follow the per-count fill tiers of Chapter 9 Table 1 (53% for one conductor, 31% for two, 40% for three or more) with the rounding rule of Note 7. Nipple counts also respect what round conductors physically pack into a round raceway, which is stricter than 60% on the largest sizes. Mixed sizes or insulations must be calculated from Tables 4 and 5; the calculator on this page does it.
Worth knowing before the pull
Jam ratio · Ch. 9 Table 1, Informational Note No. 2
Pulling three conductors, jamming can happen when the conduit inside diameter is 2.8 to 3.2 times the conductor diameter. The calculator flags that band.
Ampacity is separate · 310.15(C)(1)
Room in the pipe does not mean full ampacity. Four or more current-carrying conductors derate each other. An equipment grounding conductor counts toward fill but not toward that count · 310.15(E).
Nipples · Ch. 9 Notes, Note 4
A conduit or tubing nipple not over 24 inches between enclosures may be filled to 60%, and the ampacity adjustment factors do not apply to it.
Check a mixed pull
Different sizes or insulations in one EMT run? The calculator reads Chapter 9 Tables 4 and 5 directly and checks the fill for any combination.
Fill checked in seconds, offline.
The JobVolt app sizes raceways across seven types with the table row cited, flags jam ratio and nipples, and exports inspector-ready PDF submittals.
Common questions
- How many #12 THHN fit in 4 EMT?
- 443 conductors at the 40% fill limit, or 665 in a nipple not over 24 inches at 60% · Chapter 9 Tables 1, 4, 5 and Note 4.
- How many #10 THHN fit in 4 EMT?
- 279 conductors at the 40% fill limit, or 419 in a nipple not over 24 inches at 60% · Chapter 9 Tables 1, 4, 5 and Note 4.
- How many #8 THHN fit in 4 EMT?
- 161 conductors at the 40% fill limit, or 242 in a nipple not over 24 inches at 60% · Chapter 9 Tables 1, 4, 5 and Note 4.
- Does the ground wire count toward conduit fill?
- Yes. Equipment grounding and bonding conductors count toward the fill area · Chapter 9 Notes, Note 3. A bare conductor uses its Chapter 9 Table 8 dimensions, which are smaller than the insulated areas of Table 5 · Note 8.
- Can I use these counts for THW or XHHW in 4 EMT?
- THW is thicker than THHN, so its counts drop. XHHW depends on the size: bigger than THHN at 14 through 6 AWG, slightly smaller from 4 AWG up. Run the calculator on this page with your insulation type; it reads the exact areas from Chapter 9 Table 5.
- Does filling the conduit change the wire ampacity?
- Fill and ampacity are separate rules. Four or more current-carrying conductors in one raceway derate the ampacity of those conductors · 310.15(C)(1), however much room is left. Nipples are the exception · Chapter 9 Notes, Note 4.