NEC Chapter 9 Conduit Fill
How Many Wires Fit in 1/2" PVC?
The maximum THHN conductors per wire size in 1/2 inch PVC (Schedule 40 PVC) at the NEC 40% fill limit, with the math and the interactive calculator for any mix of wires.
Max THHN Conductors in 1/2" PVC (40% Fill)
Maximum number of same-size THHN/THWN-2 conductors in 1/2 inch PVC at the NEC Chapter 9 40% fill limit. Count the equipment ground as a conductor.
| Wire Size (THHN) | Max Conductors | Area Each (sq in) |
|---|---|---|
| #14 AWG | 11 | 0.0097 |
| #12 AWG | 8 | 0.0133 |
| #10 AWG | 5 | 0.0211 |
| #8 AWG | 3 | 0.0366 |
| #6 AWG | 2 | 0.0507 |
| #4 AWG | 1 | 0.0824 |
Based on 1/2 inch PVC internal area 0.285 sq in (NEC Chapter 9 Table 4). One conductor allows 53% fill, two allow 31%, three or more allow 40% (Table 1).
Mixed Wire Sizes? Calculate It
The chart is for one wire size at a time. For a real pull with mixed sizes, insulation types, or other conduit, enter your exact conductors for the precise fill percentage.
Frequently Asked Questions
How many wires fit in 1/2 inch PVC?
At the NEC 40% fill limit for three or more conductors, 1/2 inch PVC (internal area 0.285 sq in) holds 8 #12 THHN, 11 #14, 5 #10, or 3 #8 conductors. The math is the conduit area times 0.40 (0.285 × 0.40 = 0.114 sq in allowable), divided by the conductor's area from NEC Chapter 9 Table 5.
How many 12 AWG THHN wires fit in 1/2 inch PVC?
8 #12 THHN conductors fit in 1/2 inch PVC at the 40% fill limit. Each #12 THHN is 0.0133 sq in, so 0.114 sq in allowable ÷ 0.0133 rounds to 8 conductors (NEC Chapter 9 Note 7 rounds up when the decimal is 0.8 or more). The same count applies to THWN-2, which has the identical area.
How many #10 THHN wires fit in 1/2 inch PVC?
5 #10 THHN conductors fit in 1/2 inch PVC at the NEC 40% fill limit. Each #10 THHN is 0.0211 sq in, so 0.114 sq in allowable (0.285 × 0.40) ÷ 0.0211 rounds to 5 conductors (NEC Chapter 9 Note 7). THWN-2 has the identical area and gives the same count. Count the equipment ground as a conductor.
How many 14 AWG wires fit in 1/2 inch PVC?
11 #14 THHN conductors fit in 1/2 inch PVC at 40% fill. Each #14 THHN is 0.0097 sq in, so 0.114 sq in ÷ 0.0097 rounds to 11 (NEC Chapter 9 Note 7). Remember the ground counts as a conductor, and more than three current-carrying conductors trigger ampacity derating per NEC 310.15(C)(1).
What is the fill limit for 1/2 inch PVC?
The maximum fill depends on how many conductors are in the raceway (NEC Chapter 9, Table 1): 53% for one conductor, 31% for two, and 40% for three or more. For 1/2 inch PVC (internal area 0.285 sq in, Schedule 40 PVC) that is 0.151 sq in for one wire, 0.088 sq in for two, and 0.114 sq in for three or more. The 40% case is the common one.
Fill for Other PVC Sizes
Wires in 3/4" PVC
15 #12 THHN and the full count for 3/4 inch pipe.
Wires in 1" PVC
25 #12 THHN and the full count for 1 inch pipe.
Wires in 1-1/4" PVC
43 #12 THHN and the full count for 1-1/4 inch pipe.
Wires in 1-1/2" PVC
59 #12 THHN and the full count for 1-1/2 inch pipe.
Wires in 2" PVC
99 #12 THHN and the full count for 2 inch pipe.
Wires in 2-1/2" PVC
141 #12 THHN and the full count for 2-1/2 inch pipe.
Wires in 3" PVC
218 #12 THHN and the full count for 3 inch pipe.
Wires in 3-1/2" PVC
293 #12 THHN and the full count for 3-1/2 inch pipe.
Wires in 4" PVC
377 #12 THHN and the full count for 4 inch pipe.
1/2" in Other Conduit Types
The same 1/2 inch trade size holds a different number of wires depending on the conduit type, because each has a different internal area (NEC Chapter 9 Table 4).
1/2" EMT Fill
9 #12 THHN (EMT (electrical metallic tubing), 0.304 sq in).
1/2" RMC Fill
9 #12 THHN (RMC (rigid metal conduit), 0.314 sq in).
1/2" IMC Fill
10 #12 THHN (IMC (intermediate metal conduit), 0.342 sq in).
Conduit Fill Chart (all sizes)
Max THHN per conduit size from #14 to 500 kcmil in one table.
Fill checks out. Will the wire reach?
Getting the conductors in the pipe is one thing. Confirm the gauge holds up over distance with the voltage drop calculator before you pull.