PVC Schedule 40 Fill Chart
Common pulls for PVC Sch 40
These are the most frequent conduit fill scenarios electricians encounter on residential and light commercial jobs:
| Scenario | Conductors | Min. conduit |
|---|---|---|
| 20A 120V circuit (12 AWG) | 3 THHN (hot + neutral + ground) | 1/2" PVC Sch 40 |
| 20A 240V circuit (12 AWG) | 4 THHN (2 hot + neutral + ground) | 1/2" PVC Sch 40 |
| 30A 240V dryer (10 AWG) | 4 THHN (2 hot + neutral + ground) | 3/4" PVC Sch 40 |
| 50A 240V range (6 AWG) | 4 THHN (2 hot + neutral + ground) | 1" PVC Sch 40 |
| 200A feeder (4/0 AWG Al) | 4 (2 hot + neutral + ground) | 2" PVC Sch 40 |
Ground wire sizes per NEC Table 250.122. Actual ground wire size depends on breaker size, not conductor size.
Maximum number of same-size THHN/THWN-2 conductors permitted in PVC Sch 40 per NEC 2023 Annex C. These counts apply to conductors of the same size. Mixed sizes require area-based calculation.
| Trade Size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 11 | 8 | 5 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | - | - | - |
| 3/4" | 21 | 15 | 9 | 5 | 4 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 34 | 25 | 15 | 9 | 6 | 4 | 3 | 3 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4" | 60 | 43 | 27 | 16 | 11 | 7 | 6 | 5 | 3 | 3 | 2 | 1 | 1 |
| 1-1/2" | 82 | 59 | 37 | 21 | 15 | 9 | 8 | 7 | 5 | 4 | 3 | 3 | 2 |
| 2" | 135 | 99 | 62 | 36 | 26 | 16 | 13 | 11 | 8 | 7 | 6 | 5 | 4 |
| 2-1/2" | 193 | 141 | 89 | 51 | 37 | 22 | 19 | 16 | 12 | 10 | 8 | 7 | 6 |
| 3" | 299 | 218 | 137 | 79 | 57 | 35 | 30 | 25 | 18 | 15 | 13 | 11 | 9 |
| 3-1/2" | 401 | 293 | 184 | 106 | 77 | 47 | 40 | 33 | 25 | 21 | 17 | 14 | 12 |
| 4" | 517 | 377 | 238 | 137 | 99 | 61 | 51 | 43 | 32 | 27 | 22 | 18 | 15 |
Values are for THHN/THWN-2 conductors of the same size. NEC Annex C. For mixed conductor sizes, use the 40% fill area method per NEC Chapter 9, Table 1.
Fill rules
NEC Chapter 9 limits conduit fill to prevent overheating and allow conductor pulling:
| Conductors | Max fill |
|---|---|
| 1 conductor | 53% of conduit area |
| 2 conductors | 31% of conduit area |
| 3+ conductors | 40% of conduit area |
What to do when you're over fill
If your conductor count exceeds the Annex C value for your conduit size, you have three options:
- Upsize the conduit - go to the next trade size of PVC Sch 40. This is the simplest solution and usually the cheapest when you are close to the fill limit.
- Use a smaller-OD wire type - XHHW has a smaller diameter than THHN for the same gauge, which can save you from upsizing. This matters most at 6 AWG and larger.
- Split into two conduit runs - for long, complex pulls with many conductors, two smaller conduits may be easier to install and cheaper than one large conduit.
Real-world pull tips
PVC conduit gets slippery with lubricant, which is both an advantage and a challenge. Wire pulls through PVC Schedule 40 are generally easier than metallic conduit because there are no burrs. However, PVC expands in heat - a 100-foot run of PVC in direct sun can grow over an inch. Use expansion fittings on long runs. Glue joints must cure fully (usually 2 hours in warm weather, longer in cold) before pulling wire, or the solvent can soften and the joint can separate under tension. In cold weather below 40°F, PVC becomes brittle - don't try to bend it.
Frequently asked questions
What size PVC Sch 40 do I need for three 12 AWG THHN?
Three 12 AWG THHN conductors fit in 1/2" PVC Sch 40. This is the most common residential conduit scenario - two hots and a neutral for a 120V circuit, or hot + neutral + ground. Remember to count the equipment grounding conductor in your total.
Do ground wires count for conduit fill?
Yes. Equipment grounding conductors (EGC) must be counted when calculating conduit fill. The Annex C tables include all conductors. If you have 3 circuit conductors plus 1 ground, your count is 4 total. Some electricians mistakenly exclude the ground - this is incorrect per NEC.
When do I need to upsize the conduit?
Upsize when the conductor count exceeds the Annex C table value. Also consider upsizing for long pulls (over 100 feet), multiple bends (more than 360° total between pull points per NEC 344.26/358.26), or when pulling large conductors that could damage insulation during installation.
Can I mix different wire sizes in the same conduit?
Yes. When mixing different wire sizes, you cannot use the Annex C tables directly. Instead, use the area-based method: look up the cross-sectional area of each conductor in NEC Chapter 9 Table 5, add them up, and verify the total is under 40% of the conduit internal area (Table 4). This applies to all installations with mixed conductor sizes.
Does derating apply when I fill a conduit?
Yes. When more than 3 current-carrying conductors are in a conduit, NEC Table 310.15(C)(1) requires derating (ampacity adjustment). For 4-6 conductors, derate to 80%. For 7-9, derate to 70%. Ground wires and neutral conductors that carry only unbalanced current do not count for derating (but do count for fill). See our ampacity tables for derated values.
External resources
- NFPA 70 (NEC) - Annex C fill tables
- Southwire Conduit Fill Calculator - free online tool for mixed conductor sizes
- OSHA Electrical Safety Standards
- Mike Holt - NEC training and interpretation