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Photo of four inch PVC and EMT electrical conduit factory made elbows and EMT compression couplings

Four Inch (103mm) Electrical Conduit Dimensions

Dear Mr. Electrician:  What are the dimensions of 4" electrical conduit? Answer:  Four Inch (4″) is the trade size, not the actual dimension of electrical conduit.  One hundred and three (103) is the metric designator not the actual dimension in millimeters.  The dimensions for various types of 4″ electrical conduits are below.  The information was derived from several sources and should not be considered precise.  Dimensions may vary slightly between manufacturers. Four Inch Electrical Conduit Dimensions 4″ (103) Electrical Metallic Tubing (EMT or Thinwall) is a smooth lightweight galvanized metal conduit that has an inside diameter of 4.334" or 110.08mm.  The outside diameter is 4.500" or 114.3mm.  The wall thickness of 4″ EMT is .083" or 2.11mm.  100 feet of 4" EMT weighs approximately 393 pounds or 178.2 kilograms.  It requires a 4.5" hole for the conduit fittings.  A tap needs a 4.25" hole.  Threads per inch for the fittings is 8 NPT. 4″ (103) 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 4" RMC weighs approximately 1030 pounds or 467.1 kilograms.  It has an inside diameter of 4.026" or 102.26mm  It has an outside diameter of 4.500″ or 114.3mm.  The wall thickness is .225″ or 5.70mm.  4" Rigid requires a 4.5" hole for the conduit and fittings.  A tap needs a 4.25" hole. 4″ (103) 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 4" IMC weighs approximately  700 pounds or 317.5 kilograms.  4" IMC has an inside diameter of 4.166" or 1.5.4mm.  It has an outside diameter of 4.466″ or 113.4mm.  The wall thickness is .15″ or 3.81mm. 4″ (103) 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 4" Reduced Wall Steel Greenfield weighs approximately 270 pounds (122.47 kilograms).  Reduced Wall 4" Aluminum FMC weighs 76 pounds or 34.47 kilograms.  4" FMC has a minimum inside diameter of 4.000" or 101.6mm.  It has a minimum outside diameter of 4.360″ or 110.744mm and a maximum outside diameter of 4.560″ or 115.824mm.  The minimum bending radius is 24 inches or 609.6mm.  4" Flex requires a 4.5" hole for the conduit fittings.  A tap needs a 4.25" hole.  Threads per inch for the fittings is 8 NPT. 4″ (103) 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 4.026″ or 102.2604mm.  It has an outside diameter of 4.500″ or 114.3mm.  The wall thickness is .237″ or 6.0198mm.  4" Schedule 40 weighs 232 pounds...