Electrical Conduit Dimensions


Electrical Pipe and Conduit Dimensions From 1/2″ to 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

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

 

 

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

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

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

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.