Dear Mr. Electrician: What are the dimensions of a three-quarter-inch (3/4″) electrical conduit?
Answer: Three-Quarter Inch Electrical Conduit Dimensions are below. Three-quarter inch (3/4″) is the trade size, not the actual dimension of the electrical conduit. Twenty-One (21) is the metric designator, not the actual dimension in millimeters.
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The three-quarter inch electrical conduit dimensions information was derived from several sources and should not be considered precise. Dimensions may vary slightly between manufacturers.
Use a 1 1/8″ (29mm) hole saw for three-quarter-inch electrical conduit fittings.
Table of Contents:
- EMT
- Rigid Metal Conduit
- Intermediate Metal Conduit
- Flexible Metal Conduit
- Sealtight
- PVC 40
- PVC 80
- Smurf
- LFNC
- Fiberglass
- HDPE
- Other Conduit Sizes
- Tap and Dies
- Links
Click here to see my chart with all sizes of hole saws for electrical conduit.
THREE-QUARTER-INCH METAL ELECTRICAL CONDUIT DIMENSIONS
3/4″ Electrical Metallic Tubing (EMT or Thinwall) is a smooth, lightweight galvanized metal conduit with an inside diameter of .824″ or 20.93mm. It has an outside diameter of 0.922″ or 23.4mm. The wall thickness of 3/4″ EMT is .049″ or 1.25mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ 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.
100′ of 3/4″ RMC weighs approximately 109 pounds or 49.4 kilograms. It has an inside diameter of 0.824″ or 20.93mm. It has an outside diameter of 1.050″ or 26.7mm. The wall thickness is .107″ or 2.70mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ 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. It also utilizes the same couplings and fittings as RMC.
3/4″ IMC has an inside diameter of 0.864″ or 21.9mm. It has an outside diameter of 1.029″ or 26.1mm. The wall thickness is .083″ or 2.1mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
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3/4″ Flexible Metal Conduit (FMC or Greenfield) is a galvanized finished flexible metal electrical conduit composed of a continuously formed interlocking metal strip. 3/4″ FMC has a minimum inside diameter of 0.812″ or 20.6248mm and a maximum inside diameter of 0.835″ or 21.209mm.
Three-quarter FMC has a minimum outside diameter of 1.045″ or 26.543mm and a maximum outside diameter of 1.105″ or 28.067mm. The minimum bending radius is 5 inches or 101.6mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ 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. It has an inside minimum diameter of .820″ or 20.828mm and a maximum inside diameter of .840″ or 21.336mm.
Three-quarter inch Sealtight has a minimum outside diameter of 1.030″ or 26.162mm and a maximum outside diameter of 1.050″ or 26.67mm. The minimum bending radius is 5 inches. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
NON-METALLIC ELECTRICAL CONDUIT
3/4″ 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 with an inside diameter of 0.824″ or 20.9296mm.
Schedule 40 has an outside diameter of 1.050″ or 26.67mm. The wall thickness is .113″ or 2.8702mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ 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 limited flexibility.
Schedule 80 has an inside diameter of 0.742″ or 18.8468mm. It has an outside diameter of 1.050″ or 26.67mm. The wall thickness is .154″ or 3.9116mm. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ Electrical Nonmetallic Tubing (ENT or Smurf) is a nonmetallic, non-conductive flexible conduit with an inside diameter of .76″ or 19.304mm. 3/4″ ENT has an outside diameter of 1.05″ or 26.67mm. The minimum bend radius is 6 inches. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ Liquidtight Flexible Nonmetallic Conduit (LFNC) is a nonmetallic conduit suitable for wet conditions. It has an inside minimum diameter of .820″ or 20.828mm and a maximum inside diameter of .840″ or 21.336mm.
Three-quarter inch LFNC has a minimum outside diameter of 1.030″ or 26.162mm and a maximum outside diameter of 1.050″ or 26.67mm. The minimum bending radius is 5 inches. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ Reinforced Thermosetting Resin Conduit (RTRC) is a nonmetallic conduit suitable for many conditions. It has an inside diameter of .910″ or 23.114mm. The outside diameter is 1.050″ or 26.67mm. The conduit wall thickness is .070 or 1.778mm.
100 feet of three-quarter inch SW RTRC weighs 17 pounds or 7.711064 kilograms. It requires a 1 1/8″″ hole for the conduit fittings. A tap needs a 59/64″ hole. Threads per inch for the fittings is 14 NPT.
3/4″ High-Density Polyethylene (HDPE) is a non-metallic flexible conduit in long reel lengths to reduce joints and installation time. It has an outside diameter of 1.050″ or 26.67mm.
Three-quarter HDPE Type SDR-9 has an inside diameter of .796″ or 20.2184mm. 100 feet of 3/4″ HDPE weighs 15 pounds or 6.80388. The wall thickness is .117″ or 2.9718mm.
TAP AND DIES
All three quarter 3/4″ (21) conduit and fittings require an inch and one-eighth (1 1/8″) opening into an electrical box. The hole can be made with a hole saw or a knockout punch.
A three-quarter (3/4″) conduit or fittings tap requires a 59/64″ hole. The threads per inch is 14 National Pipe Taper (NPT). The taper is 3/4″ per foot.
However, there are NPS (National Pipe Straight) threads in some cases, such as on some fittings. NPS threads require a 15/16″ hole for a three-quarter inch NPS conduit tap.
My rule of thumb for determining if a conduit or electrical fitting is NPS or NPT is to notice if the fitting came with a locknut. If it came with a locknut, it is not meant for threading into a pipe and is an NPS thread. If you tried to screw one of these into an NPT fitting, such as a threaded condulet, it would not thread all of the ways due to the condulet having a tapered thread (NPT).
The standard length for most three quarter inch electrical conduit dimensions 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.
See my post describing various electrical conduit types with electrical code references.
MORE ELECTRICAL CONDUIT DIMENSIONS
1 1/2″ (41) 2″ (53) 2 1/2″ (63)
For more three-quarter inch electrical conduit dimensions, 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.
ELECTRICAL 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/
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