EMT vs Rigid vs IMC Conduit: Types, Differences & When to Use

Pick the wrong conduit type and you'll fail inspection, blow the budget, or both. Every electrical conduit type has a specific NEC article, a set of permitted locations, and real trade-offs in weight, cost, and bending difficulty. This reference covers the six conduit types you'll encounter most often: EMT, rigid (RMC), IMC, PVC, ENT, and flexible metallic conduit (FMC/LFMC).

Whether you're pulling wire in a commercial build-out or stubbing up conduit from an underground trench, knowing which raceway to spec saves time and keeps you code-compliant. The Conduit Bending app's bender library covers EMT, IMC, and rigid in sizes from 1/2" to 4", so you can calculate bends for whichever type the job calls for.

Conduit Types at a Glance

This table compares the six most common types of electrical conduit side by side. Use it as a quick reference when specifying conduit for a project or studying for the journeyman exam.

EMT Conduit (Electrical Metallic Tubing)

EMT is the workhorse of commercial and residential electrical work. It's the conduit you'll bend most often on the job, and the one most apprentices learn first. Covered by NEC Article 358, EMT is a thin-walled steel or aluminum raceway that doesn't use threads. Instead, it connects to boxes and fittings with set-screw or compression connectors.

Specifications

• Trade sizes: 1/2" through 4"
• Standard length: 10 feet
• Material: Galvanized steel (most common) or aluminum
• Fittings: Set-screw (dry locations) or compression (wet/damp locations)
• Support interval: Every 10 feet, within 3 feet of boxes
• Max bends between pull points: 360 degrees (four quarter bends)

Where EMT Is Permitted

EMT works in most indoor and outdoor locations. You can run it exposed on walls, above ceilings, and in concrete slabs. For outdoor use, you need compression fittings rated for wet locations. EMT is also permitted as an equipment grounding conductor per NEC 250.118, which means you don't need to pull a separate ground wire inside the raceway if the connections are made up tight with listed fittings.

Where EMT Is Not Permitted

Don't use EMT where it will take serious physical abuse. NEC 358.12 specifically prohibits EMT in locations "subject to severe physical damage." That means loading docks, parking garages at vehicle height, and similar areas call for rigid or IMC. EMT also can't be directly buried in the earth, and it's not allowed in hazardous (classified) locations unless the specific article for that location permits it.

Bending EMT

EMT is the easiest conduit type to bend. A hand bender handles 1/2" through 1-1/4" EMT without any power tools. Larger sizes (1-1/2" through 4") need a mechanical or hydraulic bender. The thin wall makes it forgiving, but it also means you can kink it if you overbend. Check the conduit bending formulas reference for deduct values and multipliers specific to each EMT size.

Rigid Metal Conduit (RMC)

Rigid conduit, formally called RMC, is the heavy-duty option. NEC Article 344 covers it. RMC has the thickest wall of any metallic conduit and uses threaded connections, which gives it the strongest mechanical joints and the best physical protection.

Specifications

• Trade sizes: 1/2" through 6"
• Standard length: 10 feet (with one coupling attached)
• Material: Galvanized steel, stainless steel, red brass, or aluminum
• Fittings: Threaded couplings and connectors
• Support interval: Every 10 feet, within 3 feet of boxes
• Max bends between pull points: 360 degrees

Where Rigid Is Permitted

RMC is permitted in all atmospheric conditions and occupancies. That includes locations subject to severe physical damage, direct burial, concrete encasement, and hazardous (classified) locations. If you're ever unsure whether the job needs heavy-duty protection, rigid is the safe bet. It also serves as an equipment grounding conductor with no additional requirements.

When to Use Rigid

Spec rigid for industrial plants, outdoor exposed runs, service entrance masts, underground feeders, and anywhere the AHJ (authority having jurisdiction) requires maximum protection. The threaded connections also make rigid the standard for areas with corrosive conditions when using red brass or stainless steel variants.

Bending Rigid

You won't bend rigid with a hand bender. Even 1/2" rigid requires a mechanical or hydraulic bender due to the thick wall. The heavier material means more effort and more setup time per bend. On the plus side, rigid holds its shape well and rarely springs back. If you're running 3-point saddle bends in rigid, you'll need accurate shrink and deduct values since mistakes cost more to fix.

IMC (Intermediate Metal Conduit)

IMC splits the difference between EMT and rigid. Covered by NEC Article 342, it has the same outside diameter as RMC but a thinner wall. That makes it about 33% lighter while being approved for all the same applications.

Specifications

• Trade sizes: 1/2" through 4"
• Standard length: 10 feet (with one coupling attached)
• Material: Steel
• Fittings: Threaded couplings and connectors (same threads as RMC)
• Support interval: Every 10 feet, within 3 feet of boxes
• Max bends between pull points: 360 degrees

EMT vs IMC: Key Differences

IMC uses threaded connections like rigid, while EMT uses set-screw or compression fittings. That threaded joint gives IMC a stronger mechanical connection. IMC is also permitted where subject to severe physical damage, something EMT can't do. But IMC costs more, weighs more, and is harder to bend than EMT. If the job spec doesn't require threaded connections or damage protection, EMT is the faster and cheaper choice.

Bending IMC

IMC requires a mechanical or hydraulic bender for most sizes. Because the wall is thinner than rigid but thicker than EMT, it falls somewhere in between for bending effort. The thinner wall (compared to RMC) also means slightly more internal area for the same trade size, so you get a small advantage on conduit fill calculations.

PVC Conduit (Rigid Polyvinyl Chloride)

PVC conduit is the go-to for underground runs and corrosive environments. NEC Article 352 covers it. Since it's plastic, it won't rust, doesn't conduct electricity, and costs less than any metallic option. That said, it has real limitations that make it wrong for many above-ground applications.

Specifications

• Trade sizes: 1/2" through 6"
• Standard length: 10 feet
• Material: Polyvinyl chloride (Schedule 40 or Schedule 80)
• Fittings: Solvent-welded (glued) or slip-fit
• Support interval: Varies by size (typically every 3 to 8 feet for exposed runs)

Schedule 40 vs Schedule 80

Where PVC Is Permitted

PVC shines underground. Direct burial, concrete encasement, and below-slab runs are its bread and butter. It's also permitted for exposed and concealed above-ground work where the temperature won't exceed its rated limits. For corrosive environments like chemical plants, wastewater facilities, and coastal installations, PVC avoids the rust problems that affect steel conduit.

Where PVC Falls Short

PVC can't serve as an equipment grounding conductor, so you always need a ground wire inside the raceway. It expands and contracts with temperature changes more than metal conduit, so long exposed runs need expansion fittings per NEC 352.44. PVC also softens at high temperatures and becomes brittle in extreme cold, limiting its use in certain environments.

Bending PVC

You don't field-bend PVC with a standard bender. Instead, you heat it with a PVC heater blanket until it softens, then form it by hand or over a form. Pre-made elbows and sweeps are available for standard angles. It's a slower process than bending EMT, but it works well for underground stub-ups and turns.

ENT (Electrical Nonmetallic Tubing)

ENT is the blue (or orange) corrugated plastic tubing you see in concrete slab work and residential rough-ins. NEC Article 362 covers it. It's flexible right out of the box, which makes it fast to install in poured slabs and through wood framing.

Specifications

• Trade sizes: 1/2" through 2"
• Material: Corrugated polyvinyl chloride
• Fittings: Snap-in or glue-on
• Flexibility: Ships in coils; bends by hand

Where ENT Is Permitted

In buildings three stories or fewer, ENT can run both exposed and concealed. In buildings above three stories, it's allowed only in concealed locations within walls, floors, and ceilings that meet fire-rating requirements, or in fully sprinklered buildings. It's commonly used in residential slab-on-grade construction, where the corrugated tube is laid out in the slab before the concrete pour.

Limitations

ENT can't be buried directly in the earth. It can't serve as an equipment grounding conductor. It's not permitted where subject to physical damage. And it's limited to 2" trade size, so it won't work for larger feeders. Think of ENT as a residential and light commercial product.

FMC and LFMC (Flexible Metal Conduit)

Flexible metal conduit (FMC, NEC Article 348) and liquidtight flexible metal conduit (LFMC, NEC Article 350) are spirally wound metal raceways designed for situations where rigid conduit can't make the connection. Motor terminations, equipment subject to vibration, and tight spaces are the classic use cases.

FMC vs LFMC

When to Use Flexible Conduit

Use FMC or LFMC for the final connection to motors, transformers, and other equipment that vibrates. Most specs limit flex conduit to 6 feet maximum for equipment grounding purposes. For longer runs, pull an equipment grounding conductor inside. Choose LFMC over FMC whenever the connection is in a wet location, outdoors, or exposed to oil or other liquids.

NEC Article Reference Summary

Each conduit type has its own article in the NEC. The structure of each article follows the same pattern: definition, permitted uses, prohibited uses, installation rules, and construction specs. Here's the quick-reference map.

For the full text of each article, refer to NFPA 70 (the National Electrical Code) or access the code through your local jurisdiction's adoption.

How to Choose the Right Conduit Type

Conduit selection starts with the environment and works backward to budget. Here's the decision process most electricians follow.

Step 1: Check for Special Requirements

Does the location have hazardous (classified) atmospheres? Is the conduit subject to severe physical damage? Will it be buried in the earth or encased in concrete? These questions eliminate most options immediately. Hazardous locations usually require rigid or IMC. Severe damage rules out EMT, ENT, PVC (Schedule 40), and flex. Direct burial limits you to RMC, IMC, PVC, or listed LFMC.

Step 2: Determine Grounding Needs

If you want the raceway itself to serve as the equipment grounding conductor (no separate green wire), you need metallic conduit: EMT, IMC, or RMC. PVC, ENT, and nonmetallic types always require a separate EGC inside.

Step 3: Consider Bending and Labor

EMT bends fast with a hand bender. Rigid and IMC need mechanical or hydraulic benders, which slows the crew down. PVC requires a heat source. For runs with multiple bends, EMT saves the most labor time. The Conduit Bending app covers deduct, gain, and multiplier values for EMT, IMC, and rigid so you can calculate any bend type regardless of which conduit you're working with. Try the free online offset bend calculator, 90-degree bend calculator, or conduit fill calculator to see how the math changes between conduit types.

Step 4: Factor in Cost

EMT and PVC are the cheapest materials. Rigid is the most expensive, with IMC falling in between. But material cost isn't the whole picture. Rigid takes more labor to cut, thread, and install. EMT's lighter weight and faster fittings often make it the lowest total installed cost for above-ground runs.

Conduit Fill by Type

Different conduit types have different internal areas even at the same trade size, because wall thickness varies. That means the number of wires you can pull through 3/4" EMT is different from 3/4" rigid. The NEC accounts for this in Chapter 9, Table 4, which lists internal areas by conduit type.

For example, 3/4" EMT (Table 4, Article 358) has an internal area of 0.556 square inches at 40% fill. The same trade size in rigid (Table 4, Article 344) has 0.526 square inches at 40% fill. IMC falls between the two. These differences matter when you're right on the edge of the fill limit.

Use our conduit fill chart for the complete NEC Chapter 9 wire count tables broken out by conduit type and wire gauge.

Conduit Bending App 16 bend types, bender library, fraction calculator. Free on iOS.