BWG (Birmingham Wire Gauge) and SWG (Standard Wire Gauge) were originally developed to measure wire diameters but are now widely used to specify tube wall thickness. The two systems use different scales and are predominant in different regions.
BWG vs. SWG Comparison
Property
BWG (Birmingham Wire Gauge)
SWG (Standard Wire Gauge)
Usage
Used in the United States; standard in tube and pipe manufacturing for boilers, heat exchangers, and other metal tubes.
Used in the United Kingdom and Commonwealth countries; applied in jewelry making, wire manufacturing, and tubing, particularly in the electrical field.
Characteristics
Defined set of thicknesses recognized in the tubing industry. Lower gauge number = thicker wall.
Lower gauge number = thicker wall. Actual thicknesses differ from BWG for the same gauge number.
Scale Variation
For a given gauge number, BWG and SWG define different thicknesses. Always clarify which gauge system is being referenced when specifying tube wall thickness.
Industry Preference
Standard for tube and pipe wall thickness in petrochemical, heating, and cooling systems.
More common in electrical wiring and in countries with historical ties to the British measurement system.
When specifying tube wall thickness, always state which gauge system applies to avoid ordering errors. The choice between BWG and SWG depends on regional practice, industry standards, and project requirements. Refer to the manufacturer’s data sheet or applicable standard for exact measurements.
Tubing & Instrumentation
Tubing is used extensively in instrumentation for oil and gas, chemical processing, power generation, and pharmaceutical plants. Instrumentation tubing connects instruments, valves, and other devices in systems that measure, monitor, and control process variables such as pressure, flow, temperature, and level.
Features of Instrumentation Tubing
Feature
Description
Precision and Reliability
Instrumentation tubing has tighter dimensional tolerances and smoother interior surfaces than standard tubing, reducing turbulence and flow resistance for accurate signal transmission and fluid transport.
Material Selection
Stainless steel (typically 316SS) is the most common material due to its corrosion resistance and broad fluid compatibility. Copper, alloy steel, and plastic are selected based on chemical compatibility, temperature range, and environment.
Size and Configuration
Typically small diameter, from 1/4 inch to 1 inch OD. Connected with compression or welded fittings. Size, wall thickness, and material selection directly affect system performance.
Pressure and Temperature Ratings
Must withstand operating pressures and temperatures without loss of integrity or measurement accuracy. Pressure ratings, temperature limits, and thermal expansion must be verified against service conditions.
Safety and Compliance
Must comply with applicable industry standards and safety regulations covering design, testing, and material composition.
Proper tubing selection and installation directly affect measurement accuracy and system reliability. Material, size, and wall thickness must be matched to the specific process conditions and applicable standards.
Tubing Dimension & Weight Charts
By “BWG” Wall Thickness (Birmingham Wire Gauge)
“BWG” Tubing Size Chart: steel tubing sizes by OD (inches/mm) and WT (BWG Gauges 22 to 10), with weight by OD/WT combination in Lbs/ft and Kg/m (according to ASTM A450 Specification)
BWG Gauge Wall Thickness Reference
Gauge
WT (inch)
WT (mm)
G. 22
0.028
0.711
G. 20
0.035
0.889
G. 18
0.049
1.244
G. 16
0.065
1.650
G. 14
0.083
2.108
G. 12
0.109
2.768
G. 11
0.120
3.047
G. 10
0.134
3.403
BWG Tubing Weight (lb/ft)
Tube OD
OD (mm)
G. 22
G. 20
G. 18
G. 16
G. 14
G. 12
G. 11
G. 10
1/4″
6.350
-
0.082
0.107
0.130
-
-
-
-
5/16″
7.950
-
0.106
0.140
0.175
-
-
-
-
3/8″
9.525
-
0.129
0.173
0.219
0.263
-
-
-
1/2″
12.700
0.143
0.177
0.240
0.307
0.376
0.362
0.495
-
5/8″
15.875
0.181
0.224
0.306
0.395
0.489
0.610
0.658
-
3/4″
19.050
-
0.271
0.373
0.483
0.601
0.759
0.820
0.894
7/8″
22.225
0.257
0.319
0.439
0.572
0.712
0.907
0.981
1.080
1″
25.400
0.296
0.367
0.505
0.660
0.826
1.060
1.150
1.260
1-1/4″
31.750
0.372
0.462
0.638
0.833
1.060
1.350
1.470
1.630
1-1/2″
38.100
0.448
0.556
0.773
1.010
1.280
1.650
1.800
1.990
1-3/4″
44.450
0.523
0.652
0.907
1.190
1.510
1.940
2.120
2.350
2″
50.800
0.599
0.746
1.040
1.360
1.730
2.240
2.450
2.710
2-1/2″
63.500
-
-
1.300
1.720
2.180
2.830
3.100
3.440
3″
76.200
-
-
1.570
2.070
2.630
3.420
3.750
4.170
3-1/2″
88.900
-
-
1.830
2.430
3.080
4.010
4.400
4.900
4″
101.600
-
-
2.100
2.780
3.530
4.600
5.050
5.620
BWG Tubing Weight (kg/m)
Tube OD
OD (mm)
G. 22
G. 20
G. 18
G. 16
G. 14
G. 12
G. 11
G. 10
1/4″
6.350
-
0.122
0.159
0.194
-
-
-
-
5/16″
7.950
-
0.157
0.209
0.260
-
-
-
-
3/8″
9.525
-
0.192
0.258
0.326
0.392
-
-
-
1/2″
12.700
0.213
0.263
0.357
0.457
0.559
0.668
0.737
-
5/8″
15.875
0.270
0.334
0.456
0.558
0.727
0.908
0.979
-
3/4″
19.050
-
0.404
0.555
0.719
0.894
1.130
1.220
1.330
7/8″
22.225
0.383
0.475
0.654
0.851
1.060
1.350
1.460
1.600
1″
25.400
0.440
0.546
0.752
0.982
1.230
1.570
1.710
1.870
1-1/4″
31.750
0.553
0.687
0.950
1.240
1.570
2.010
2.190
2.420
1-1/2″
38.100
0.666
0.828
1.150
1.510
1.900
2.450
2.680
2.960
1-3/4″
44.450
0.779
0.970
1.350
1.770
2.240
2.890
3.160
3.500
2″
50.800
0.892
1.110
1.540
2.030
2.570
3.330
3.650
4.040
2-1/2″
63.500
-
-
1.940
2.560
3.240
4.210
4.610
5.120
3″
76.200
-
-
2.340
3.080
3.910
5.090
5.580
6.200
3-1/2″
88.900
-
-
2.730
3.610
4.580
5.970
6.550
7.290
4″
101.600
-
-
3.130
4.130
5.250
6.850
7.520
8.370
By “SWG” Wall Thickness (Standard Wire Gauge)
“SWG” Tubing Size Chart: steel tubing sizes by OD (inches/mm) and WT (SWG Gauges 22 to 10), with weight by OD/WT combination in Lbs/ft and Kg/m (according to ASTM A450 Specification)
SWG Gauge Wall Thickness Reference
Gauge
WT (inch)
WT (mm)
G. 22
0.028
0.711
G. 20
0.036
0.914
G. 18
0.048
1.218
G. 16
0.064
1.625
G. 14
0.080
2.032
G. 12
0.104
2.641
G. 11
0.116
2.946
G. 10
0.128
3.251
SWG Tubing Weight (lb/ft)
Tube OD
OD (mm)
G. 22
G. 20
G. 18
G. 16
G. 14
G. 12
G. 11
G. 10
1/4″
6.350
-
0.083
0.105
0.129
-
-
-
-
5/16″
7.950
-
0.108
0.138
0.173
-
-
-
-
3/8″
9.525
-
0.132
0.170
0.216
0.256
-
-
-
1/2″
12.700
0.143
0.181
0.235
0.303
0.365
0.447
0.484
-
5/8″
15.875
0.181
0.230
0.300
0.390
0.473
0.588
0.641
-
3/4″
19.050
-
0.279
0.366
0.476
0.582
0.732
0.800
0.867
7/8″
22.225
0.257
0.328
0.431
0.563
0.692
0.874
0.954
1.040
1″
25.400
0.296
0.376
0.496
0.650
0.800
1.020
1.120
1.210
1-1/4″
31.750
0.372
0.474
0.626
0.827
1.020
1.300
1.430
1.560
1-1/2″
38.100
0.448
0.572
0.759
0.994
1.240
1.580
1.740
1.910
1-3/4″
44.450
0.523
0.669
0.887
1.170
1.450
1.860
2.060
2.250
2″
50.800
0.599
0.766
1.020
1.340
1.670
2.140
2.370
2.600
2-1/2″
63.500
-
-
1.280
1.690
2.100
2.710
3.000
3.300
3″
76.200
-
-
1.540
2.040
2.530
3.270
3.630
3.990
3-1/2″
88.900
-
-
1.790
2.390
2.970
3.830
4.260
4.680
4″
101.600
-
-
2.060
2.740
3.410
4.400
4.890
5.380
SWG Tubing Weight (kg/m)
Tube OD
OD (mm)
G. 22
G. 20
G. 18
G. 16
G. 14
G. 12
G. 11
G. 10
1/4″
6.350
-
0.124
0.157
0.192
-
-
-
-
5/16″
7.950
-
0.161
0.205
0.257
-
-
-
-
3/8″
9.525
-
0.197
0.253
0.321
0.381
-
-
-
1/2″
12.700
0.213
0.270
0.350
0.451
0.543
0.665
0.720
-
5/8″
15.875
0.270
0.342
0.447
0.580
0.704
0.875
0.954
-
3/4″
19.050
-
0.415
0.544
0.709
0.866
1.090
1.190
1.290
7/8″
22.225
0.383
0.488
0.641
0.838
1.030
1.300
1.420
1.550
1″
25.400
0.440
0.560
0.738
0.967
1.190
1.510
1.660
1.800
1-1/4″
31.750
0.553
0.706
0.931
1.230
1.510
1.930
2.130
2.320
1-1/2″
38.100
0.666
0.851
1.130
1.480
1.840
2.350
2.590
2.840
1-3/4″
44.450
0.779
0.996
1.320
1.740
2.160
2.770
3.060
3.350
2″
50.800
0.892
1.140
1.510
2.000
2.480
3.190
3.530
3.970
2-1/2″
63.500
-
-
1.900
2.520
3.130
4.030
4.470
4.910
3″
76.200
-
-
2.290
3.030
3.770
4.870
5.400
5.940
3-1/2″
88.900
-
-
2.670
3.550
4.420
5.700
6.340
6.970
4″
101.600
-
-
3.060
4.070
5.070
6.540
7.280
8.010
Bwg/swg Conversion Charts (gauge To Mm/inch)
Tube SWG gauge conversion into inches and millimeters
SWG
SWG Gauge in inches
SWG Gauge in mm
0 Tube SWG
0.324
8.23
1 Tube SWG
0.3
7.62
2 Tube SWG
0.276
7.01
3 Tube SWG
0.252
6.4
4 Tube SWG
0.232
5.89
5 Tube SWG
0.212
5.38
6 Tube SWG
0.192
4.88
7 Tube SWG
0.176
4.47
8 Tube SWG
0.16
4.06
9 Tube SWG
0.144
3.66
10 Tube SWG
128
3.25
11 Tube SWG
0.116
2.95
12 Tube SWG
0.104
2.64
13 Tube SWG
0.092
2.34
14 Tube SWG
0.08
2.03
15 Tube SWG
0.072
1.83
16 Tube SWG
0.064
1.63
17 Tube SWG
0.056
1.42
18 Tube SWG
0.048
1.22
19 Tube SWG
0.04
1.02
20 Tube SWG
0.036
0.91
21 Tube SWG
0.032
0.81
22 Tube SWG
0.028
0.71
23 Tube SWG
0.024
0.61
24 Tube SWG
0.022
0.56
25 Tube SWG
0.02
0.51
26 Tube SWG
0.018
0.46
27 Tube SWG
0.0164
0.42
28 Tube SWG
0.0148
0.38
29 Tube SWG
0.0136
0.35
30 Tube SWG
0.0124
0.31
31 Tube SWG
0.0116
0.29
32 Tube SWG
0.0108
0.27
33 Tube SWG
0.01
0.25
34 Tube SWG
0.0092
0.23
35 Tube SWG
0.0084
0.21
36 Tube SWG
0.0076
0.19
BWG
BWG Gauge to inches
BWG Gauge in mm
0 Tube BWG
0.34
8.64
1 Tube BWG
0.3
7.62
2 Tube BWG
0.284
7.21
3 Tube BWG
0.259
6.58
4 Tube BWG
0.238
6.05
5 Tube BWG
0.22
5.59
6 Tube BWG
0.203
5.16
7 Tube BWG
0.18
4.57
8 Tube BWG
0.165
4.19
9 Tube BWG
0.148
3.76
10 Tube BWG
0.134
3.4
11 Tube BWG
0.12
3.05
12 Tube BWG
0.109
2.77
13 Tube BWG
0.95
2.41
14 Tube BWG
0.083
2.11
15 Tube BWG
0.072
1.83
16 Tube BWG
0.065
1.65
17 Tube BWG
0.058
1.47
18 Tube BWG
0.049
1.24
19 Tube BWG
0.042
1.07
20 Tube BWG
0.035
0.89
21 Tube BWG
0.032
0.81
22 Tube BWG
0.028
0.71
23 Tube BWG
0.025
0.64
24 Tube BWG
0.022
0.56
25 Tube BWG
0.02
0.51
26 Tube BWG
0.018
0.46
27 Tube BWG
0.016
0.41
28 Tube BWG
0.014
0.36
29 Tube BWG
0.013
0.33
30 Tube BWG
0.012
0.3
31 Tube BWG
0.01
0.25
32 Tube BWG
0.009
0.23
33 Tube BWG
0.008
0.2
34 Tube BWG
0.007
0.18
35 Tube BWG
0.005
0.13
36 Tube BWG
0.004
0.1
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Previous Comments
Chas
I pay a quick visit everyday a few web pages and information sites to read articles or reviews, however this weblog gives feature based content.
Eric R pagan
please any you this side and price .. thanks .21 Tube SWG 0.032 0.81
SteveR
Dear Sirs/Madams, I believe the wall thickness values, in inches, are a factor of 10x too high for the tubes of gauge 18, 16, 14, and 12. No criticism here; I've made many mistakes in my life! Just trying to help.
paulchris
I want to say you thank you for your Post I really like to read your post in future please keep it up.. Thank you It’s really very nice post
carol
Clarified my doubts and provided me the knowledge required to confidently source the material required. top job. Thank You one and all
Nelson B
I'm looking to buy the following tubings: ASTM A-179 BWG 12 Diameter: 1″ Length: 20′ Quantity: 2876
Stacy
Dear Sirs. My name is Stacy, I’m a purchasing Manager of an Innotex system company. We are a Kazakhstan company, we are engaged in the production and installation of charging stations for electric cars. We opened a representative office in Europe in the field of renewable energy . We are interested in purchasing a metal profile for installation of solar panels. We would buy samples for the test. We are ready to regard the quotation for more quantity 40*40 – 12 meters, wall thickness 2mm – 1 pc. 50*50 – 12 meters, wall thickness 2 mm. – 1 pc. If that is possible we would like you to deliver that city of Espoo.
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Leave a Comment
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Previous Comments
I pay a quick visit everyday a few web pages and information sites to read articles or reviews, however this weblog gives feature based content.
please any you this side and price .. thanks .21 Tube SWG 0.032 0.81
Dear Sirs/Madams, I believe the wall thickness values, in inches, are a factor of 10x too high for the tubes of gauge 18, 16, 14, and 12. No criticism here; I've made many mistakes in my life! Just trying to help.
I want to say you thank you for your Post I really like to read your post in future please keep it up.. Thank you It’s really very nice post
Clarified my doubts and provided me the knowledge required to confidently source the material required. top job. Thank You one and all
I'm looking to buy the following tubings: ASTM A-179 BWG 12 Diameter: 1″ Length: 20′ Quantity: 2876
Dear Sirs. My name is Stacy, I’m a purchasing Manager of an Innotex system company. We are a Kazakhstan company, we are engaged in the production and installation of charging stations for electric cars. We opened a representative office in Europe in the field of renewable energy . We are interested in purchasing a metal profile for installation of solar panels. We would buy samples for the test. We are ready to regard the quotation for more quantity 40*40 – 12 meters, wall thickness 2mm – 1 pc. 50*50 – 12 meters, wall thickness 2 mm. – 1 pc. If that is possible we would like you to deliver that city of Espoo.