PVC Conduit Fill Chart & Wire Sizing Guide (NEC)

IMPORTANT
Quick Summary: Under the National Electrical Code (NEC Article 352 and Annex C Table C.10), the maximum number of conductors permitted in Schedule 40 Rigid PVC Conduit depends on the cross-sectional area of the wire and the conduit trade size. When pulling three or more conductors of the same size and insulation type (THHN/THWN-2), the standard capacities are:
1/2″ Schedule 40 PVC: 11 wires of 14 AWG | 8 wires of 12 AWG | 5 wires of 10 AWG | 2 wires of 6 AWG
3/4″ Schedule 40 PVC: 22 wires of 14 AWG | 16 wires of 12 AWG | 10 wires of 10 AWG | 4 wires of 6 AWG
1″ Schedule 40 PVC: 35 wires of 14 AWG | 26 wires of 12 AWG | 16 wires of 10 AWG | 6 wires of 6 AWG
1-1/4″ Schedule 40 PVC: 61 wires of 14 AWG | 45 wires of 12 AWG | 28 wires of 10 AWG | 11 wires of 6 AWG

Key Takeaways

The 40 Percent Standard (NEC Chapter 9 Table 1): For runs containing three or more conductors, total wire cross-sectional area cannot exceed 40% of the Schedule 40 PVC conduit interior area.
One and Two Conductor Limits: Single-conductor pulls are permitted up to 53% fill, while two-conductor pulls are strictly limited to 31% fill to prevent conductors from wedging and binding during installation.
Underground Wet Location Mandate (NEC 300.5(B)): The interior of all underground PVC conduit is legally classified as a wet location. You must use wet-rated conductors such as THWN-2 or XHHW-2 (standard indoor NM-B Romex is strictly prohibited).
Schedule 40 vs. Schedule 80 Capacity: Schedule 40 PVC has thinner walls and a larger inside diameter than Schedule 80 PVC, allowing it to hold significantly more conductors per trade size.

Schedule 40 PVC Fill Limits At-A-Glance

NEC Chapter 9, Table 1 Allowable Cross-Sectional Fill Ratios

53%

1 Conductor

Single wire pulls

31%

2 Conductors

Prevents line jamming

40%

3+ Conductors

Standard run limit

60%

24″ Nipple

Short meter sleeves

Master Schedule 40 PVC Conduit Fill Chart (NEC Annex C Table C.10)

The table below provides the maximum allowable number of conductors for compact copper THHN/THWN-2 conductors inside Schedule 40 Rigid PVC Conduit from 1/2 inch to 4 inches based on NEC Chapter 9 Table 4 (40% fill limit for 3 or more wires).

Conductor Size (AWG/kcmil)	Wire Area (sq. in.)	1/2″ PVC (0.114 sq. in.)	3/4″ PVC (0.213 sq. in.)	1″ PVC (0.346 sq. in.)	1-1/4″ PVC (0.600 sq. in.)	1-1/2″ PVC (0.814 sq. in.)	2″ PVC (1.342 sq. in.)	2-1/2″ PVC (1.918 sq. in.)	3″ PVC (2.954 sq. in.)	3-1/2″ PVC (3.938 sq. in.)	4″ PVC (5.000 sq. in.)
14 AWG THHN	0.0097	11	22	35	61	84	138	197	304	406	515
12 AWG THHN	0.0133	8	16	26	45	61	101	144	222	296	376
10 AWG THHN	0.0211	5	10	16	28	38	63	90	140	186	237
8 AWG THHN	0.0366	3	5	9	16	22	36	52	80	107	136
6 AWG THHN	0.0507	2	4	6	11	16	26	37	58	77	98
4 AWG THHN	0.0824	1	2	4	7	9	16	23	35	47	60
3 AWG THHN	0.0973	1	2	3	6	8	13	19	30	40	51
2 AWG THHN	0.1159	0	1	2	5	7	11	16	25	33	43
1 AWG THHN	0.1339	0	1	2	4	6	10	14	22	29	37
1/0 AWG THHN	0.1562	0	1	2	3	5	8	12	18	25	32
2/0 AWG THHN	0.1863	0	0	1	3	4	7	10	15	21	26
3/0 AWG THHN	0.2223	0	0	1	2	3	6	8	13	17	22
4/0 AWG THHN	0.2679	0	0	0	2	3	5	7	11	14	18
250 kcmil (MCM)	0.3970	0	0	0	1	2	3	4	7	9	12
300 kcmil (MCM)	0.4608	0	0	0	0	1	2	4	6	8	10
350 kcmil (MCM)	0.5242	0	0	0	0	1	2	3	5	7	9
400 kcmil (MCM)	0.5863	0	0	0	0	1	2	3	5	6	8
500 kcmil (MCM)	0.7073	0	0	0	0	0	1	2	4	5	7

Underground electrical trench with gray Schedule 40 PVC conduit and color-coded THWN-2 copper wires

[!PRO TIP] Custom Multi-Gauge Trench Calculations: Mixing different wire gauges or pulling heavy aluminum feeders? Calculate exact multi-conductor trench requirements with our Interactive Conduit Fill Calculator.

Schedule 40 PVC Dimensions and Internal Area Reference (NEC Table 4)

Schedule 40 PVC features a standard wall thickness engineered for underground direct burial, concrete encasement, and general surface mounting. The table below outlines internal dimensions and legal fill limits.

PVC Trade Size	Internal Diameter (in.)	Total Internal Area (100%)	1 Wire (53% Fill Limit)	2 Wires (31% Fill Limit)	3+ Wires (40% Fill Limit)	24″ Nipple (60% Fill Limit)
1/2″	0.602 in.	0.286 sq. in.	0.152 sq. in.	0.089 sq. in.	0.114 sq. in.	0.172 sq. in.
3/4″	0.804 in.	0.533 sq. in.	0.283 sq. in.	0.165 sq. in.	0.213 sq. in.	0.320 sq. in.
1″	1.029 in.	0.864 sq. in.	0.458 sq. in.	0.268 sq. in.	0.346 sq. in.	0.518 sq. in.
1-1/4″	1.360 in.	1.500 sq. in.	0.795 sq. in.	0.465 sq. in.	0.600 sq. in.	0.900 sq. in.
1-1/2″	1.590 in.	2.036 sq. in.	1.079 sq. in.	0.631 sq. in.	0.814 sq. in.	1.222 sq. in.
2″	2.047 in.	3.356 sq. in.	1.779 sq. in.	1.040 sq. in.	1.342 sq. in.	2.014 sq. in.
2-1/2″	2.445 in.	4.795 sq. in.	2.541 sq. in.	1.486 sq. in.	1.918 sq. in.	2.877 sq. in.
3″	3.042 in.	7.385 sq. in.	3.914 sq. in.	2.289 sq. in.	2.954 sq. in.	4.431 sq. in.
3-1/2″	3.521 in.	9.845 sq. in.	5.218 sq. in.	3.052 sq. in.	3.938 sq. in.	5.907 sq. in.
4″	3.998 in.	12.500 sq. in.	6.625 sq. in.	3.875 sq. in.	5.000 sq. in.	7.500 sq. in.

Important NEC Installation Rules for Schedule 40 PVC

When designing and installing Schedule 40 PVC conduit systems, adhere to these critical code requirements:

Underground Minimum Burial Depths (NEC Table 300.5): Schedule 40 PVC requires a minimum burial depth of 18 inches under general dirt, lawns, and gardens (reduced to 12 inches for residential branch circuits protected by a 20A GFCI breaker). Under driveways and commercial parking lots, minimum depth is 24 inches.
Expansion Fittings for Thermal Movement (NEC 352.44): PVC expands and contracts significantly with temperature changes (approximately 4.1 inches per 100 feet for a 100°F temperature shift). Expansion fittings are mandatory on long outdoor runs to prevent buckled conduit.
Physical Damage Protection (Schedule 40 vs. Schedule 80): While Schedule 40 PVC is standard underground, NEC 352.10(F) mandates Schedule 80 PVC where conduit is exposed to severe physical damage (such as vehicle driveway risers or loading docks).
Bend Radius and Pull Points (NEC 352.26): Total bends between pull boxes cannot exceed 360 degrees. Review our 360-degree conduit bend limit guide to prevent damaged cable jackets.

NEC Table 300.5 Schedule 40 PVC Burial Depth Rules:

18 Inches

Standard general trench depth in earth or lawns.

12 Inches

Residential 120V circuits with 20A GFCI protection.

24 Inches

Under commercial streets, highways, and parking lots.

Frequently Asked Questions (FAQs)

How many 10 AWG wires can fit in 1/2 inch PVC conduit?

Under NEC Annex C Table C.10, you can install up to 5 conductors of 10 AWG THHN/THWN-2 in 1/2-inch Schedule 40 PVC conduit.

What size PVC conduit do I need for a 100 amp subpanel?

A standard 100-amp subpanel using three 2 AWG copper conductors plus one 8 AWG ground requires a minimum 1-1/4-inch Schedule 40 PVC conduit.

Can you run Romex (NM-B) in underground PVC conduit?

No. Under NEC Section 300.5(B), underground conduit is legally classified as a wet location. Standard indoor Romex has paper fillers and non-waterproof insulation. You must pull THWN-2, XHHW-2, or UF-B cable.

Does Schedule 40 PVC hold the same number of wires as Schedule 80 PVC?

No. Schedule 80 PVC has thicker walls and a smaller inside diameter, meaning it holds fewer conductors than Schedule 40 PVC.

Dedicated Schedule 40 PVC Wire Sizing Guides

Explore individual wire gauge fill capacities and specific trade size breakdown tables:

Small Branch Circuit Gauges:

View capacity limits for 14 AWG in Schedule 40 PVC for 15A underground landscape runs.
View capacity limits for 12 AWG in Schedule 40 PVC for 20A outdoor GFCI circuits.
View capacity limits for 10 AWG in Schedule 40 PVC for 30A water heater and AC trench feeds.

Medium Feeder & Subpanel Gauges:

View capacity limits for 8 AWG in Schedule 40 PVC for 40A range and heat pump circuits.
View capacity limits for 6 AWG in Schedule 40 PVC for 50A EV chargers and hot tubs.
View capacity limits for 4 AWG in Schedule 40 PVC for 70A and 80A garage subpanels.
View capacity limits for 3 AWG in Schedule 40 PVC for 100A subpanels.
View capacity limits for 2 AWG in Schedule 40 PVC for 100A and 115A feeders.
View capacity limits for 1 AWG in Schedule 40 PVC for 125A commercial feeds.

Heavy Service Entrance & Commercial Cables:

View capacity limits for 1/0 AWG in Schedule 40 PVC for 150A services.
View capacity limits for 2/0 AWG in Schedule 40 PVC for 175A feeders.
View capacity limits for 3/0 AWG in Schedule 40 PVC for 200A residential underground laterals.
View capacity limits for 4/0 AWG in Schedule 40 PVC for 225A services.
View capacity limits for 250 MCM in Schedule 40 PVC for commercial distribution runs.
View capacity limits for 300 MCM in Schedule 40 PVC for 300A distribution panels.
View capacity limits for 350 MCM in Schedule 40 PVC for parallel switchgear feeds.
View capacity limits for 400 MCM in Schedule 40 PVC for heavy commercial mains.
View capacity limits for 500 MCM in Schedule 40 PVC for utility transformer laterals.