Four Inch Electrical Conduit Dimensions

Dimensions of Various Types of Four Inch Electrical Conduit

Dear Mr. Electrician:  What are the actual four inch electrical conduit dimensions?

Answer:  The dimensions for various types of 4″ electrical conduits are below.  Four Inch (4″) is the trade size, not the actual dimension of the electrical conduit.  One hundred and three (103) is the metric designator, not the exact dimension in millimeters.

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The information was derived from several sources and should not be considered precise.  Dimensions may vary slightly between manufacturers.

Use a 4 1/2″ (114mm) hole saw for four-inch conduit fittings.

Table of Contents:

Click here for my article with more detailed descriptions of various types of electrical conduit and their code references without dimensions.

METAL ELECTRICAL CONDUIT


4″ Electrical Metallic Tubing (EMT or Thinwall) is a smooth, lightweight galvanized metal conduit with 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.

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4″ 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.

Four-inch RMC 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.  A 4″ Rigid conduit requires a 4.5″ hole for the conduit and fittings.  A tap needs a 4.25″ hole.

4″ 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.

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4″ 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.

Four-inch 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″ Liquidtight Flexible Metal Conduit (LFMC or Sealtight) is a flexible metal conduit with a non-metallic, non-conductive outer jacket that makes it suitable for use in wet locations.  100 feet of 4″ Sealtight weighs 349 pounds or 158.303608 kilograms.

Four Inch LFMC has an inside minimum diameter of 4.000″ or 101.6mm and a maximum inside diameter of 4.040″ or mm.  It has a minimum outside diameter of 4.460″ or 113.284mm and a maximum outside diameter of 4.500″ or 114.3mm.  The minimum bending radius is 24 inches (609.6mm).  Fittings require a 4.5″ hole.  A tap needs a 4.25″ hole.  Threads per inch for the fittings is 8 NPT.

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FOUR-INCH NON-METALLIC ELECTRICAL CONDUIT


4″ 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.

Four-inch PVC 40 has an inside diameter of 4.026″ or 102.2604mm and an outside diameter of 4.500″ or 114.3mm.  The wall thickness is .237″ or 6.0198mm.  4″ Schedule 40 weighs 232 pounds per 100 feet (105.233344 kilograms).

4″ PVC 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″ Rigid Polyvinyl Chloride Conduit (PVC) schedule 80 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors or underground.  It has minimal flexibility.

Four Inch Schedule 80 PVC has an inside diameter of 3.826″ or 97.1804mm.  It has an outside diameter of 4.500″ or 114.3mm.  The wall thickness is .337″ or 8.5598mm.

4″ PVC 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.  100′ of PVC 80 weighs approximately 308 pounds.

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4″ Reinforced Thermosetting Resin Conduit (RTRC or Fiberglass) is a nonmetallic conduit that is suitable for many conditions.  It has an inside diameter of 4.320″ or 109.728mm.  The outside diameter is 4.460″ or 113.284mm.  The conduit wall thickness is .070″ or 1.778mm.

100 feet of four-inch SW RTRC weighs 72 pounds or 32.658624 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″ High-Density Polyethylene (HDPE) is a non-metallic flexible conduit available in long reel lengths to reduce joints and installation time.  It has an outside diameter of 4.500″ or 114.3mm.

Four-inch HDPE Type SDR-9 has an inside diameter of 3.440″ or 87.376mm.  100 feet of 4″ HDPE weighs 272 pounds or 123.377024 kilograms.  The wall thickness is 0.500″ or 12.7mm.

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All four-inch conduit and fittings require a four-and-a-half-inch (4 1/2″ or 114mm) opening into an electrical box.  The hole can be made with a hole saw or a knockout punch.

A tap for a four-inch (4″) (103) conduit or conduit fittings requires a 4 1/4″ hole.  The threads per inch is 8 National Pipe Thread (NPT).

The standard length for most conduits is ten feet (10′) or 3.048 meters.  Twenty-foot (20′) (6.096 meters) lengths of metal conduit are available but not always in stock.  PVC conduit is available in ten-foot (10′) and, in some sizes, twenty-foot (20′) lengths.

RTRC mostly comes in twenty-foot (20′) lengths.  The flexible conduits come in various length coils and reels depending on the trade size.  Some electrical supply companies will cut flexible conduits to length.

Click here for my chart of all hole saw sizes for electrical conduit.

Emergency disconnect, service disconnect sticker label as required by the National Electrical Code. Click on the image to see more Emergency Disconnect Stickers in my Redbubble Store.
Emergency disconnect, service disconnect sticker label as required by the National Electrical Code. Click on the image to see more Emergency Disconnect Stickers in my Redbubble Store.

OTHER ELECTRICAL CONDUIT DIMENSIONS

1/2″ (16)       3/4″ (21)        1″(27)

1 1/4″ (35)       1 1/2″ (41)        2″ (53)

2 1/2″ (63)       3″ (78)        3 1/2″ (91)

5″ (129)       6″ (155)

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For more conduit code details and conduit fill, see Chapter 9, Tables 1, 4, 5, and 5A.
See the tables in Informative Annex C in the back of the National Electrical Code (NFPA 70) for the allowable number of wires in each size conduit.

LINKS TO CONDUIT MANUFACTURERS

Aluminum and Steel Conduit Products – https://www.westerntube.com/

Fiberglass Conduit Products – https://championfiberglass.com/

PVC Conduit products – https://www.cantexinc.com/

Steel Conduit Products – https://www.alliedeg.us/

Visit my Link Tree for my social media connections and links to merchandise in my Redbubble Shop.

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