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Close shot of an inch and one quarter EMT conduit bender

Inch and a Quarter (35mm) Electrical Conduit Dimensions

Dear Mr. Electrician:  What are the dimensions of 1 1/4" electrical conduit? Answer:  One Inch and a Quarter (1 1/4″) is the trade size, not the actual dimension of electrical conduit.  Thirty Five (35) is the metric designator not the actual dimension in millimeters.  The dimensions for various types of 1 1/4″ electrical conduits are below.  The information was derived from several sources and should not be considered precise.  Dimensions may vary slightly between manufacturers.  NOTE: Text links below go to applicable products on Amazon.com One Inch & One Quarter Conduit Dimensions 1 1/4″ (35) Electrical Metallic Tubing (EMT or Thinwall) is a smooth lightweight galvanized metal conduit that has an inside diameter of 1.380" or 35.05mm.  The outside diameter is 1.510" or 38.35mm.  The wall thickness of 1 1/4″ EMT is 0.065" or 1.65mm.  100 feet of 1 1/4" EMT weighs approximately 101 pounds or 45.8 kilograms.  It requires a 1 3/4" hole for the conduit fittings.  A tap needs a 1 1/2" hole.  Threads per inch for the fittings is 11.5 NPT. 1 1/4″ (35) Rigid Metal Conduit (RMC) is a heavy weight conduit with a galvanized finish throughout.  It has factory threads 11.5 NPT with a 3/4″ per foot taper.  100′ of 1 1/4" RMC weighs approximately 218 pounds or 98.9 kilograms.  It has an inside diameter of 1.380" or 35.05mm.  It has an outside diameter of 1.660″ or 42.2mm.  The wall thickness is .133″ or 3.40mm.  1 1/4" Rigid requires a 1 3/4" hole for the conduit and fittings.  A tap needs a 1 1/2" hole. 1 1/4″ (35) 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 11.5 threads per inch NPT.  It also utilizes the same couplings and fittings as RMC.  100 feet of 1 1/4" IMC weighs approximately 158 pounds or 71.7 kilograms.  1 1/4" IMC has an inside diameter of 1.468" or 36.8mm.  It has an outside diameter of 1.638″ or 41.6mm.  The wall thickness is .095″ or 2.41mm. The 1 1/4" bender above can also be used for one inch rigid and 1" aluminum electrical conduit.  There are formulas that electricians use to calculate the degree angle and length for elbows, offsets, and saddle bends.  The electrical conduit bender has a long handle that is not shown in this photo. 1 1/4″ (35) 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 1 1/4" Reduced Wall Steel Greenfield weighs approximately 65 pounds (29.48 kilograms).  Reduced Wall 1 1/4" Aluminum FMC weighs 24 pounds or 10.88 kilograms.  1 1/4" FMC has a minimum inside diameter of 1.250" or 31.75mm and a maximum inside diameter of 1.300″ or 33.02mm.  It has a minimum outside diameter of 1.550″ or 39.37mm and a maximum outside diameter of 1.630″ or 41.40mm.  The minimum...