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Electrical Pipe and Conduit Dimensions from  1/2" - 6"

Trade Size
USA
Trade Size
Metric
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
4" 103
5" 129
6" 155
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At the bottom of this page, pertinent references are made to the "National Electrical Code" concerning the use of the different types of pipe and electrical conduit for wiring.  Electrical conduit lengths are given below with the metric equivalent.  There is a hole saw chart down below for each size conduit.
The information below was derived from several sources and should not be considered precise.  Actual dimensions can vary slightly between manufacturers. This chart will be updated as more information becomes available. Not responsible for errors and omissions.
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches 
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
1/2" EMT 16 0.622" 15.80 0.706" 17.93       7/8"
(Fitting opening)
Tap for fittings same as rigid
1/2" IMC 16 0.660" 16.8 0.815"       14 7/8" 23/32" or 3/4"
1/2" RMC 16 0.622" 15.80 0.840" 21.34 27/32"   14 7/8" 23/32" or 3/4"
1/2" Flexible
FMC
16 0.625" 16.1 0.920         7/8"
(Fitting opening)
Tap for fittings same as rigid
1/2" PVC
40
16 0.622" 15.80 0.840" 21.34   .109"   7/8"
(Fitting opening)
Tap for fittings same as rigid
1/2" PVC
80
16 0.546" 13.87 0.840" 21.34   .147"   7/8"
(Fitting opening)
Tap for fittings same as rigid
1/2" ENT 16     0.840"         7/8"
(Fitting opening)
 
1/2" Liquid
Tight

Flexible Metal
Conduit
LFMC
16 .622"   0.840         7/8"
(Fitting opening)
Tap for fittings same as rigid
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
3/4" EMT 21 0.824" 20.93 0.922" 23.42       1 1/8"
(
Fitting opening)
Tap for fittings same as rigid
3/4" IMC 21 0.864" 21.9 1.029"       14 1 1/8" 59/64" or 7/8"
3/4" RMC 21 0.824" 20.93 1.050" 26.67 1 & 3/64"   14 1 1/8" 59/64" or 7/8"
3/4" Flexible
FMC
21 0.812" 20.9 1.105"         1 1/8"
(
Fitting opening)
Tap for fittings same as rigid
3/4" PVC
40
21 0.824" 20.93 1.050" 26.67   0.113"   1 1/8"
(
Fitting opening)
Tap for fittings same as rigid
3/4 " PVC
80
21 0.742" 18.85 1.050" 26.67   0.154"   1 1/8"
(
Fitting opening)
Tap for fittings same as rigid
3/4" ENT 21     1.050"         1 1/8"
(
Fitting opening)
 
3/4"
Liquid
Tight

Flexible Metal
Conduit
LFMC
21 0.820"   1.050"         1 1/8"
(
Fitting opening)
Tap for fittings same as rigid
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 Pipe Fitters Blue Book
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
 Threads per inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
1" EMT 27 1.049" 26.64 1.163" 29.54     1 3/8"
(
Fitting opening)
Tap for fittings same as rigid
1" IMC 27 1.120" 28.1 1.290"       11.5 1 3/8" 1-5/32"or 1 1/8"
1" RMC 27 1.049" 26.64 1.315" 33.4 1 & 5/16"   11.5 1 3/8" 1-5/32" or 1 1/8"
1" Flexible
FMC
27 1.020" 25.9           1 3/8"
(
Fitting opening)
Tap for fittings same as rigid
1" PVC
40
27 1.049" 26.64 1.315" 33.40   .133"   1 3/8"
(
Fitting opening)
Tap for fittings same as rigid
1" PVC
80
27 .957" 24.31 1.315" 33.40   .179"   1 3/8"
(
Fitting opening)
Tap for fittings same as rigid
1" ENT 27     1.315"         1 3/8"
(
Fitting opening)
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
1 1/4" EMT 35 1.380" 35.05 1.510" 38.35       1 3/4"
(
Fitting opening)
Tap for fittings same as rigid
1 1/4" IMC 35 1.468" 36.8 1.638"       11.5 1 3/4" 1-1/2"
1 1/4" RMC 35 1.380" 35.05 1.660" 42.16 1 & 21/32"   11.5 1 3/4" 1-1/2"
1 1/4" Flexible
FMC
35 1.275" 32.4           1 3/4"
(
Fitting opening)
Tap for fittings same as rigid
1 1/4" PVC
40
35 1.380" 35.05 1.660" 42.16   .140"   1 3/4"
(
Fitting opening)
Tap for fittings same as rigid
1 1/4" PVC
80
35 1.278" 32.46 1.660" 42.16   .191"   1 3/4"
(
Fitting opening)
Tap for fittings same as rigid
1 1/4" ENT 35     1.660"         1 3/4"
(
Fitting opening)
 
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
1 1/2" EMT 41 1.610" 40.89 1.740" 44.20       1 7/8"
(
Fitting opening)
Tap for fittings same as rigid
1 1/2" IMC 41 1.703" 42.7 1.883"       11.5 1 7/8" 1-47/64" or 1 3/4"
1 1/2" RMC 41 1.610" 40.89 1.900" 42.86 1 & 29/32"   11.5 1 7/8" 1-47/64" or 1 3/4"
1 1/2" Flexible
FMC
41 1.538" 39.1           1 7/8"
(
Fitting opening)
Tap for fittings same as rigid
1 1/2" PVC
40
41 1.610" 40.89 1.900" 48.26   .145"   1 7/8"
(
Fitting opening)
Tap for fittings same as rigid
1 1/2" PVC
80
41 1.50" 38.10 1.900" 48.26   .200"   1 7/8"
(
Fitting opening)
Tap for fittings same as rigid
1 1/2" ENT 41     1.990"         1 7/8"
(
Fitting opening)
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
2" EMT 53 2.067" 52.50 2.197" 55.80       2 1/2"
(
Fitting opening)
Tap for fittings same as rigid
2" IMC 53 2.170" 54.6 2.360"       11.5 2 1/2" 2-7/32" or 2 1/4"
2" RMC 53 2.067 52.50 2.375" 60.33 2 & 3/8"   11.5 2 1/2" 2-7/32" or 2 1/4"
2" Flexible
FMC
53 2.040" 51.8           2 1/2"
(
Fitting opening)
Tap for fittings same as rigid
2" PVC
40
53 2.067" 52.50 2.375" 60.33   .154"   2 1/2"
(
Fitting opening)
Tap for fittings same as rigid
2" PVC
80
53 1.939" 49.25 2.375" 60.33   .218"   2 1/2"
(
Fitting opening)
Tap for fittings same as rigid
2" ENT 53     2.375"         2 1/2"
(
Fitting opening)
 
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
2 1/2" EMT 63 2.731" 69.4 2.875"         3"
(
Fitting opening)
Tap for fittings same as rigid
2 1/2" IMC 63 2.597" 64.9 2.857"       8 3" 2-5/8"
2 1/2" RMC 63 2.469" 62.71 2.875" 73.03 2 & 7/8"   8 3" 2-5/8"
2 1/2" Flexible
FMC
63 2.500" 63.5           3"
(
Fitting opening)
Tap for fittings same as rigid
2 1/2" PVC
40
63 2.469" 62.71 2.875" 73.03   .203"   3"
(
Fitting opening)
Tap for fittings same as rigid
2 1/2" PVC
80
63 2.323" 59.00 2.875" 73.03   .276"   3"
(
Fitting opening)
Tap for fittings same as rigid
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
3" EMT 78 3.356" 85.24 3.500" 88.90       3 5/8"
(
Fitting opening)
Tap for fittings same as rigid
3"
IMC
78 3.216" 80.7 3.476"       8 3 5/8" 3-1/4"
3"
RMC
78 3.068" 77.93 3.500" 88.90 3 & 1/2"   8 3 5/8" 3-1/4"
3" Flexible
FMC
78 3.000" 76.2           3 5/8"
(
Fitting opening)
Tap for fittings same as rigid
3" PVC
40
78 3.068" 77.93 3.500" 88.90   .216"   3 5/8"
(
Fitting opening)
Tap for fittings same as rigid
3" PVC
80
78 2.900" 73.66 3.500" 88.90   .300"   3 5/8"
(
Fitting opening)
Tap for fittings same as rigid
 
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
3 1/2" EMT 91 3.834" 97.4 4.00"         4 1/8"
(
Fitting opening)
Tap for fittings same as rigid
31/2" IMC 91 3.671" 93.2         8 4 1/8" 3-3/4"
3 1/2" RMC 91 3.548" 90.12 4.00" 101.6 4"   8 4 1/8" 3-3/4"
3 1/2" Flexible
FMC
91 3.500" 88.9           4 1/8"
(
Fitting opening)
Tap for fittings same as rigid
3 1/2" PVC
40
91 3.548" 90.12 4.000" 101.60   .226"   4 1/8"
(
Fitting opening)
Tap for fittings same as rigid
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
 
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
4" EMT 103 4.334" 110.08 4.500" 114.30       4 1/2"
(
Fitting opening)
Tap for fittings same as rigid
4" IMC 103 4.166" 105.4     4 & 1/2"   8 4 1/2" 4-1/4"
4"RMC 103 4.026" 102.26 4.500" 114.30     8 4 1/2" 4-1/4"
4" Flexible FMT 103 4.000" 101.6           4 1/2"
(
Fitting opening)
Tap for fittings same as rigid
4" PVC
40
103 4.026" 102.26 4.500" 114.30   .237"   4 1/2"
(
Fitting opening)
Tap for fittings same as rigid
4" PVC
80
103 3.826" 97.18 4.500" 114.30   .337"   4 1/2"
(
Fitting opening)
Tap for fittings same as rigid
 
Click Pipe Size 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 3 1/2" 4" 5" 6"
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
NPT
Size Opening Needed Into Box Drill for Tap
NPT
5"PVC
40
129 5.047" 128.19 5.563" 141.30   .258"   5 5/8"  
5"PVC
80
129 4.813" 122.25 5.563" 141.30   .375"   5 5/8"  
Trade Size
USA
Trade Size
Metric
Inside Diameter
Inches
Inside Diameter
MM
Outside Diameter
Inches
Outside Diameter
MM
Fractional Outside Diameter Inches Wall
Thickness 
Threads per Inch
(NPT)
Size Opening Needed Into Box Drill for Tap
(NPT)
6"PVC
40
155 6.065" 154.05 6.625" 168.28   .280"   6 3/8"  
6"PVC
80
155 5.761" 146.33 6.625" 168.28   .432"   6 3/8"  
 
 
National Electrical Code Sections for Electrical Conduit
EMT (Electrical Metallic Tubing AKA Thinwall) - Article 358
Intermediate Metal Conduit (IMC) - Article 342
Rigid Metal Conduit (RMC) - Article 344
Flexible Metal Conduit (FMC) - Article 348
PVC Conduit - Article 352
Liquidtight Flexible Nonmetallic Conduit - Article 356
Liquidtight Flexible Metal Conduit (LFMC) - Article 350
ENT (Electrical Nonmetallic Tubing) - Article 362
Also see Chapter 9, Table 4 for more details.
See Informative Annex C in the back of the NEC for the allowable number of wires in each size conduit.
 
The standard length for electrical conduit is ten feet (10').  Some sizes of PVC and EMT also come in twenty foot lengths (20'), however they may be difficult to find in stock.  Start by calling local electrical supply companies in your area.  Flexible conduit comes in varying lengths depending on the size.  Smaller sizes can be up to 100' while the larger sizes may only be available in lengths as short as 25'.  Many supply houses will cut flexible conduit to order so there is no need to buy a full coil.
10' (Ten feet) of conduit =  120" (Inches)
10' (Ten feet) of conduit = 3.333333333 Yards
10' (Ten feet) of conduit = 3048 Millimeters
10' (Ten feet) of conduit = 304.8 Centimeters
10' (Ten feet) of conduit = 30.48 Decimeters
10' (Ten feet) of conduit = 3.048 Meters
For 1/2" conduit, drill using a 7/8" hole saw  
For 3/4" conduit, drill using a 1 1/8" hole saw 
For 1" conduit, drill using a 1 3/8" hole saw  
For 1 1/4" conduit, drill using a 1 3/4" hole saw  
For 1 1/2" conduit, drill using a 1 7/8" hole saw  
For 2" conduit, drill using a 2 1/2" hole saw  
 
 
For 2 1/2" conduit, drill using a 3" hole saw  
For 3" conduit, drill using a 3 5/8" hole saw  
For 3 1/2" conduit, drill using a 4 1/8" hole saw  
For 4" conduit, drill using a 4 1/2" hole saw  
For 5" conduit, use a 5 5/8" Knockout Punch
For 6" conduit, use a 6 3/8" Knockout Punch
 
 
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Updated December 13, 2015

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