Electrical Conduit Dimensions

Electrical Conduit Dimensions Chart

This page has been updated here: Electrical Conduit Types and Dimensions

Electrical Pipe and Conduit Dimensions From 1/2″ to 6″.  This page is best viewed horizontally.

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

 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
16 .622″ 0.840 7/8″

(Fitting
opening)
Tap
for fittings same as rigid

 

 

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
21 0.820″ 1.050″ 1
1/8″
(
Fitting
opening)
Tap
for fittings same as rigid

 

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)

 



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
31/2″ 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
31/2″ 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

See my post about the different types of electrical conduits in use in North America.