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  • Stainless steel tubes
SWG / BWG Reference

Tube Dimensions & Gauge Weights

Wall thickness and theoretical weight per metre for every gauge, from 1/4" to 4" outside diameter — in both Standard and Birmingham Wire Gauge.

17 Tube Sizes1/4" to 4" OD (6.35–101.6 mm)
8 Gauges10, 12, 14, 16, 18, 19, 20, 22
SWG & BWGStandard & Birmingham Wire Gauge
Weight per MetreTheoretical, in kg/m

Find Tube Dimensions

Choose a tube size and a gauge to read off the wall thickness, inside diameter and theoretical weight per metre. The full reference chart is below.

QUICK GAUGE

Tube Dimensions — SWG / BWG reference — theoretical weight per metre (kg/m)
Size
(inch)		 OD
(mm)		 Gauge 10 Gauge 12 Gauge 14 Gauge 16 Gauge 18 Gauge 19 Gauge 20 Gauge 22
SWG BWG SWG BWG SWG BWG SWG BWG SWG BWG SWG BWG SWG BWG SWG BWG
3.251 mm 3.404 mm 2.642 mm 2.769 mm 2.032 mm 2.108 mm 1.626 mm 1.651 mm 1.219 mm 1.245 mm 1.016 mm 1.067 mm 0.914 mm 0.889 mm 0.711 mm 0.711 mm
1/4" 6.35 — — — — 0.218 0.222 0.191 0.192 0.155 0.158 0.134 0.140 0.123 0.120 0.099 0.099
5/16" 7.93 — — — — 0.297 0.305 0.254 0.257 0.203 0.206 0.174 0.182 0.159 0.155 0.127 0.127
3/8" 9.52 0.506 0.517 0.451 0.464 0.377 0.388 0.318 0.322 0.251 0.256 0.214 0.224 0.195 0.190 0.155 0.155
1/2" 12.70 0.762 0.785 0.659 0.682 0.538 0.554 0.447 0.453 0.347 0.354 0.295 0.308 0.267 0.261 0.211 0.211
5/8" 15.87 1.018 1.053 0.867 0.900 0.698 0.720 0.575 0.582 0.443 0.452 0.374 0.392 0.339 0.330 0.267 0.267
3/4" 19.05 1.274 1.321 1.076 1.118 0.858 0.886 0.703 0.713 0.539 0.550 0.455 0.476 0.411 0.401 0.323 0.323
1" 25.40 1.786 1.858 1.492 1.555 1.178 1.219 0.959 0.973 0.731 0.746 0.615 0.644 0.555 0.541 0.436 0.435
1 1/4" 31.82 2.304 2.400 1.913 1.996 1.502 1.555 1.218 1.236 0.925 0.944 0.776 0.814 0.701 0.682 — —
1 1/2" 38.10 2.811 2.930 2.324 2.427 1.818 1.883 1.471 1.493 1.115 1.138 0.935 0.980 0.843 0.821 — —
1 3/4" 45.45 3.404 3.551 2.806 2.932 2.189 2.268 1.768 1.794 1.338 1.365 1.120 1.175 1.010 0.983 — —
2" 50.80 3.825 4.003 3.157 3.300 2.459 2.548 1.984 2.013 1.499 1.531 1.255 1.317 1.131 1.101 — —
2 1/4" 57.15 4.347 4.539 3.573 3.736 2.779 2.880 2.240 2.273 1.692 1.727 1.415 — — — — —
2 1/2" 63.50 4.860 5.075 3.989 4.172 3.099 3.212 2.496 2.533 1.884 1.923 1.575 — — — — —
2 3/4" 69.85 5.372 5.612 4.405 4.608 3.419 3.544 2.752 2.794 2.076 2.119 1.735 — — — — —
3" 76.20 5.884 6.148 4.822 5.045 3.739 3.877 3.008 3.054 — — — — — — — —
3 1/2" 88.90 6.908 7.220 5.654 5.917 4.379 4.541 — — — — — — — — — —
4" 101.60 7.933 8.293 6.487 6.790 5.020 5.206 — — — — — — — — — —

Cells show theoretical weight in kg/m for the wall thickness of that gauge. Calculated as WT = (OD − t) × t × 0.02481; mill tolerance is excluded. A dash means that gauge is not listed against that outside diameter.

Note: values are reproduced from the MBM reference chart. Confirm against your project specification before ordering — our technical team is happy to verify a size for you.

How a tube is measured

OD
ID
t

Tube is ordered by actual outside diameter and gauge. The gauge fixes the wall, and the bore follows from the two.

ID = OD − (2 × t) t = (OD − ID) ÷ 2 WT = (OD − t) × t × 0.02481

What the numbers mean

OD
Outside Diameter

Tube is specified by its actual outside diameter, not a nominal size. A 1" tube measures 25.40 mm across, unlike 1" pipe which measures 33.40 mm.

SWG
Standard Wire Gauge

The British gauge series. Gauge 16 SWG is 1.626 mm. A higher gauge number means a thinner wall.

BWG
Birmingham Wire Gauge

The series normally used for heat exchanger and condenser tube. Gauge 16 BWG is 1.651 mm — close to SWG but not identical, so always state which you mean.

t
Wall Thickness

Set by the gauge rather than by a schedule. The bore follows from the outside diameter and twice the wall.

Table of Gauges — Standard Wire Gauge (SWG) and Birmingham Wire Gauge (BWG)
Gauge Unit 10 12 14 16 18 19 20 22
S.W.G.Standard Wire Gauge Inch 0.128 0.104 0.080 0.064 0.048 0.040 0.036 0.028
mm 3.251 2.642 2.032 1.626 1.219 1.016 0.914 0.711
B.W.G.Birmingham Wire Gauge Inch 0.134 0.109 0.083 0.065 0.049 0.042 0.036 0.028
mm 3.404 2.769 2.108 1.651 1.245 1.067 0.889 0.711
SWG — Standard Wire Gauge, the British series.BWG — Birmingham Wire Gauge, used for heat exchanger and condenser tube.Higher gauge number = thinner wall.

Tube products we manufacture

SMLS
Seamless Tubes

Cold drawn and pilgered seamless stainless steel tube.
WLD
Welded Tubes

TIG welded tube in a full range of grades and finishes.
HX
Heat Exchanger Tubes

BWG gauges for heat exchanger and condenser duty.
INST
Instrumentation Tubes

Small bore tube for instrumentation and process lines.

Need a size not listed?

MBM Tubes manufactures stainless steel seamless and welded tubes in various grades, sizes, gauges and specifications as per customer requirements.

Send your requirement WhatsApp MBM Tube Dimensions Chart

Frequently Asked Questions

What is the difference between tube and pipe?

Tube is specified by its actual outside diameter and a wall thickness or gauge; pipe is specified by a nominal size and a schedule. A 1" tube is 25.40 mm OD, while 1" pipe is 33.40 mm OD.

What is the difference between SWG and BWG?

They are two different gauge series. SWG (Standard Wire Gauge) is the British system; BWG (Birmingham Wire Gauge) is normally used for heat exchanger and condenser tube. At gauge 14 SWG is 2.032 mm and BWG is 2.108 mm, so the weight differs — always state which series you are working to.

Does a higher gauge number mean a thicker wall?

No, the opposite. Gauge numbers run inversely to thickness: gauge 10 is 3.251 mm SWG while gauge 22 is 0.711 mm. The heavier the wall, the lower the gauge number.

How is the theoretical weight calculated?

WT = (OD − t) × t × 0.02481, with OD and t in millimetres, giving kilograms per metre. The figures shown are theoretical and exclude mill tolerance.

Why do some cells show a dash?

A dash means that gauge is not offered against that outside diameter in the reference. Heavier gauges start at 3/8", and the lighter gauges stop as the diameter grows.

Can you supply sizes outside this chart?

Yes. We manufacture stainless steel seamless and welded tube beyond this range and to intermediate walls. Send us the OD, wall and grade and we will confirm.

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