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Three Inch (78) Electrical Conduit Dimensions

Dear Mr. Electrician:  What are the dimensions of 3" electrical conduit? Answer:  Three Inch (3″) is the trade size, not the actual dimension of electrical conduit.  Seventy eight (78) is the metric designator not the actual dimension in millimeters.  The dimensions for various types of 3″ electrical conduits are below.  The information was derived from several sources and should not be considered precise.  Dimensions may vary slightly between manufacturers. Three Inch Electrical Conduit Dimensions 3″ (78) Electrical Metallic Tubing (EMT or Thinwall) is a smooth lightweight galvanized metal conduit that has an inside diameter of 3.356" or 85.24mm.  The outside diameter is 3.500" or 88.9mm.  The wall thickness of 3″ EMT is .072" or 1.83mm.  100 feet of 3" EMT weighs approximately 263 pounds or 119.3 kilograms.  It requires a 3 5/8" hole for the conduit fittings.  A tap needs a 3 1/4" hole.  Threads per inch for the fittings is 8 NPT. 3″ (78) Rigid Metal Conduit (RMC) is a heavy weight conduit with a galvanized finish throughout.  It has factory threads with a 3/4″ per foot taper, 8 threads per inch NPT.  100′ of 3" RMC weighs approximately 727 pounds or 329.7 kilograms.  It has an inside diameter of 3.068" or 77.93mm and an outside diameter of 3.500″ or 88.9mm.  The wall thickness is .205″ or 5.20mm.  3" Rigid requires a 3 5/8" hole for the conduit and fittings.  A tap needs a 3 1/4" hole. 3″ (78) Intermediate Metal Conduit (IMC) is a lighter weight version of RMC.  It has a galvanized finish inside and out and can be used in many of the same environments as RMC.  It has factory threads with a 3/4″ per foot taper, and 8 threads per inch NPT.  It also utilizes the same couplings and fittings as RMC.  100 feet of 3" IMC weighs approximately 543 pounds or 246.3 kilograms.  3" IMC has an inside diameter of 3.216" or 80.7mm.  It has an outside diameter of 3.476″ or 88.3mm.  The wall thickness is .15″ or 3.81mm. 3″ (78) Flexible Metal Conduit (FMC or Greenfield) is a galvanized finished flexible metal electrical conduit composed of a continuously formed interlocking metal strip.  100 feet of 3" Reduced Wall Steel Greenfield weighs approximately 190 pounds (86.18248 kilograms).  Reduced Wall 3" Aluminum FMC weighs 77 pounds or 34.926584 kilograms.   3" FMC has a minimum inside diameter of 3.000" or 76.2mm.  It has a minimum outside diameter of 3.360″ or 85.344mm and a maximum outside diameter of 3.560″ or 90.424mm.  The minimum bending radius is 18 inches or 457.2mm.  3" Flex requires a 3 5/8" hole for the conduit fittings.  A tap needs a 3 1/4" hole.  Threads per inch for the fittings is 8 NPT. 3″ (78) Rigid Polyvinyl Chloride Conduit (PVC) schedule 40 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors, or underground.  It has some flexibility with an inside diameter of 3.068″ or 77.9272mm.  It has an outside diameter of 3.500″ or 88.9mm.  The wall thickness is .216″ or 5.4864mm.  3" Schedule 40...