EMT vs PVC vs RMC vs IMC: Which Conduit Should You Use?

EMT (electrical metallic tubing) is thin-wall steel used for exposed, dry, indoor and light commercial runs; it is bent with a hand bender and joined with set-screw or compression fittings, no threading. PVC is rigid non-metallic conduit used where moisture, corrosion, or direct burial rule out steel: wet locations, underground, and corrosive environments. PVC is non-conductive, so it needs an equipment grounding conductor pulled inside, while EMT's steel can serve as the ground path when properly assembled. PVC also has a larger internal area than EMT of the same trade size, so it holds slightly more or fewer conductors depending on the schedule.

Both are threaded rigid steel conduit that provide the strongest physical protection and are allowed in hazardous locations. IMC (intermediate metal conduit) has a thinner wall than RMC (rigid metal conduit), so it is lighter and cheaper and has a larger internal area for the same trade size, which means it holds more conductors. RMC is heavier and more robust, preferred where maximum mechanical protection or specific listings are required. For most applications where rigid metal is needed, IMC does the job at lower weight and cost; RMC is chosen when the job or engineer specifically calls for it.

PVC (Schedule 40 for most direct burial, Schedule 80 where physical damage is a concern such as exposed risers) is the most common underground conduit because it does not corrode. RMC and IMC are also permitted underground and are used where extra strength is needed, often with supplementary corrosion protection. EMT is not suitable for direct burial. Always follow the NEC burial-depth requirements in Table 300.5 for the wiring method you choose.

Yes. Fill is 40% of the conduit's internal area (NEC Chapter 9), and each type has a different internal area for the same trade size (Table 4). For example, 3/4 inch conduit holds 16 #12 THHN in EMT, 16 in RMC, 15 in Schedule 40 PVC, and 17 in IMC, because IMC has the largest internal area and PVC the smallest of this group at that size. Use the per-type calculators below for any size.

Yes, EMT is permitted outdoors and in wet locations when used with fittings listed as raintight or concrete-tight and assembled correctly (NEC 358.10). What EMT cannot do is direct burial or areas subject to severe physical damage, where rigid metal (RMC/IMC) or PVC is required instead. In corrosive environments, steel EMT needs supplementary protection or a switch to PVC.