Conduit Fill Chart
The Conduit Fill Chart is a electrical reference tool covering conduit fill chart, conduit fill calculator, nec conduit fill chart, conduit fill percentage. Use the chart below to look up values instantly. Printable and downloadable versions are available on this page.
Conduit Fill Chart — NEC Requirements
NEC Article 40 specifies the maximum percentage of a conduit's internal cross-sectional area that can be filled with conductors — these limits ensure adequate heat dissipation and allow conductors to be pulled through without damage.
| Number of Conductors | Maximum Fill Percentage | Notes |
|---|---|---|
| 1 conductor | 53% | Single conductor in a conduit or raceway |
| 2 conductors | 31% | Two conductors |
| 3 or more conductors | 40% | Standard for most installations |
Source: National Electrical Code (NEC) Article 40 — NFPA 70
EMT Conduit Fill Chart — Number of Conductors by Wire Size
| Wire Size (AWG or kcmil) | 1/2" EMT | 3/4" EMT | 1" EMT | 1-1/4" EMT | 1-1/2" EMT | 2" EMT | 2-1/2" EMT |
|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 22 | 35 | 61 | 84 | 138 | 171 |
| 12 AWG | 9 | 16 | 26 | 45 | 61 | 101 | 126 |
| 10 AWG | 5 | 10 | 16 | 28 | 38 | 63 | 78 |
| 8 AWG | 3 | 5 | 8 | 14 | 19 | 31 | 39 |
| 6 AWG | 1 | 4 | 7 | 12 | 16 | 26 | 33 |
| 4 AWG | 1 | 2 | 4 | 7 | 10 | 16 | 20 |
| 3 AWG | 1 | 1 | 4 | 6 | 9 | 14 | 18 |
| 2 AWG | 1 | 1 | 3 | 5 | 7 | 12 | 15 |
| 1 AWG | 1 | 1 | 1 | 4 | 5 | 9 | 11 |
| 1/0 AWG | 1 | 1 | 1 | 3 | 4 | 7 | 9 |
| 2/0 AWG | — | 1 | 1 | 2 | 3 | 6 | 7 |
| 3/0 AWG | — | 1 | 1 | 1 | 3 | 5 | 6 |
| 4/0 AWG | — | — | 1 | 1 | 2 | 4 | 5 |
| 250 kcmil | — | — | 1 | 1 | 1 | 3 | 4 |
Source: NEC 2023 Annex C — Conduit and Tubing Fill Tables for Conductors and Fixture Wires
Conduit Types Reference
| Conduit Type | Material | Best Applications | Key Properties |
|---|---|---|---|
| EMT Electrical Metallic Tubing | Thin-wall steel | Commercial interiors, offices, exposed runs in dry locations | Lightest steel conduit. Not suitable for direct burial or wet locations without fittings. Most common in commercial construction. |
| IMC Intermediate Metal Conduit | Galvanised steel | Indoor and outdoor above-ground applications | Heavier than EMT but lighter than rigid. Suitable for some wet locations. |
| RMC Rigid Metal Conduit | Galvanised steel or aluminium | Outdoor, wet locations, direct burial, corrosive environments | Heaviest and most durable metal conduit. Full 10-foot sticks with threads. |
| PVC Rigid Non-Metallic Conduit | Schedule 40 or 80 PVC | Direct burial, underground, concrete encasement, wet locations | Corrosion-resistant. Cannot be used in exposed locations where mechanical damage risk exists unless Schedule 80. |
| ENT Electrical Non-Metallic Tubing | Corrugated PVC | In-wall and in-concrete residential applications | Flexible for bending — not for exposed locations. Blue or orange corrugated appearance. |
| FMC Flexible Metal Conduit | Steel spiral | Final connection to equipment subject to vibration, motors, HVAC | Not suitable for long runs. Used for equipment connections requiring movement or vibration isolation. |
Conduit Fill Calculator
Select your conduit type and size, add wire types and quantities, then calculate total fill percentage. The calculator flags NEC compliance and suggests the next conduit size up if you are over the fill limit.
Frequently Asked Questions
What is conduit fill?
Conduit fill refers to the percentage of a conduit's internal cross-sectional area that is occupied by conductors. The NEC limits fill to 40 percent for three or more conductors to prevent heat buildup and allow the conductors to be pulled through without damage.
How many 12 AWG wires can fit in 1/2-inch EMT?
According to NEC conduit fill tables for THHN/THWN conductors a 1/2-inch EMT conduit can hold up to 9 conductors of 12 AWG wire at the 40 percent fill limit for three or more conductors. Always verify against the full NEC Annex C table for your specific conductor insulation type.
What is the difference between EMT and PVC conduit?
EMT is a thin-wall steel conduit used primarily in commercial interiors — it provides good mechanical protection but is not rated for direct burial or wet locations without appropriate fittings. PVC conduit is non-metallic, corrosion-resistant, and suitable for direct burial and underground applications.
Do I need conduit for residential wiring?
Most residential wiring uses NM-B (Romex) cable in wood-framed construction where it is protected inside walls and does not require conduit. Conduit is required for exposed wiring runs in garages, workshops, basements, and exterior locations.
What size conduit do I need for a 100-amp service?
A 100-amp residential service typically uses 2 AWG copper conductors (or 1/0 AWG aluminium) which requires at minimum a 1-inch conduit for three conductors at 40 percent fill. Always confirm with your local electrical inspector as requirements vary.
How is conduit fill calculated?
Calculate the total cross-sectional area of all conductors (in square inches or mm²) and compare it to 40 percent of the conduit's interior cross-sectional area. The NEC provides pre-calculated Annex C tables for common conductor and conduit size combinations — use those tables rather than manual calculation in most situations.
What is the maximum conduit fill for 2 wires?
For exactly 2 conductors the NEC limits fill to 31 percent of the conduit's interior cross-sectional area. This is more restrictive than the 40 percent limit for 3 or more conductors.
What type of conduit is best for outdoor use?
RMC (Rigid Metal Conduit) and Schedule 80 PVC are both suitable for outdoor exposed locations. For underground or direct burial applications Schedule 40 PVC is most common and cost-effective — metallic conduits require coated or aluminium versions for direct burial to resist corrosion.