Birmingham gauge

TheBirmingham gauge,^[1]officially theBirmingham Wire Gaugeand often abbreviated asGorga,^[2]is unit orwire gaugeused to measure the thickness or diameter of wires and tubing, includinghypodermic needlesand other medical tube products.

Terminology

The Birmingham gauge is also known as theStubs Iron Wire GaugeorBirmingham Wire Gaugeand is distinct from the Stubs Steel Wire Gauge and theBritish Standard Wire Gauge.It is commonly referred to simply asgauge(abbreviated asG),^[3]but this should not be confused with theFrench gauge,a separate system used for measuring the outer diameter ofcatheters.

System

The Birmingham gauge ranges from 5/0 or 00000, the lowest gauge number corresponding to the largest size of 0.500 inches (12.7 mm), to 36, the highest gauge number corresponding to the smallest size of 0.004 inches (0.10 mm). The increments between gauge sizes are not linear and vary.^[2]At higher gauge numbers, the increment between the two highest gauges is 0.001 inches (0.025 mm), while at lower gauge numbers, the increment between the two lowest gauges is 0.046 inches (1.2 mm). This progression does not follow a mathematical formula but instead reflects historical manufacturing practices in thewire drawingindustry, where the size increments were determined by practical tooling, such as adraw plate,and production constraints.^[4]In applications involving wires and fine tubing, the gauge number refers to the product's outside diameter. For larger mechanical tubing, however, the gauge number indicates the wall thickness, independent of the tube's overall size.

Inmedicine,the Birmingham gauge is widely used to specify the outer diameter ofhypodermic needles,catheters,cannulae,andsuturewires. However, catheters are more commonly defined using theFrench catheter gauge.The Birmingham gauge was originally developed in early 19th-century England for wire manufacturing and became common in medical settings in the early 20th century.

The Birmingham gauge system is also recognized in international medical standards, such as ISO 6009:2016, which includes a color-coding system for hypodermic needles. This standardization helps ensure accurate identification and compatibility of medical equipment.

Sizes of hypodermic needles

Hypodermic needlesare available in a wide variety of outer diameters described by gauge numbers. Smaller gauge numbers indicate larger outer diameters.^[5]Inner diameter depends on both gauge and wall thickness. The following chart shows nominal inner diameter and wall thickness for regular-wall needles.^[5]^[6]Thin-wall needles (not shown) have identical outer diameters but larger inner diameters for a given gauge.

Gauge, G	Nominal outer diameter		Nominal inner diameter^[a]		Nominal wall thickness^[a]		ISO6009 color^[7]
Gauge, G	(inch)	(mm)	(inch)	(mm)	(inch)	(mm)	ISO6009 color^[7]
7	0.180 ± 0.001	4.572 ± 0.025	0.150 ± 0.003	3.810 ± 0.076	0.015 ± 0.001	0.381 ± 0.025	(undefined)
8	0.165 ± 0.001	4.191 ± 0.025	0.135 ± 0.003	3.429 ± 0.076	0.015 ± 0.001	0.381 ± 0.025	(undefined)
9	0.148 ± 0.001	3.759 ± 0.025	0.118 ± 0.003	2.997 ± 0.076	0.015 ± 0.001	0.381 ± 0.025	(undefined)
10	0.134 ± 0.001	3.404 ± 0.025	0.106 ± 0.003	2.692 ± 0.076	0.014 ± 0.001	0.356 ± 0.025	Olive brown
11	0.120 ± 0.001	3.048 ± 0.025	0.094 ± 0.003	2.388 ± 0.076	0.013 ± 0.001	0.330 ± 0.025	Green-yellow
12	0.109 ± 0.001	2.769 ± 0.025	0.085 ± 0.003	2.159 ± 0.076	0.012 ± 0.001	0.305 ± 0.025	Pale blue
13	0.095 ± 0.001	2.413 ± 0.025	0.071 ± 0.003	1.803 ± 0.076	0.012 ± 0.001	0.305 ± 0.025	Purple
14	0.083 ± 0.001	2.108 ± 0.025	0.063 ± 0.003	1.600 ± 0.076	0.010 ± 0.001	0.254 ± 0.025	Pale green
15	0.0720 ± 0.0005	1.829 ± 0.013	0.0540 ± 0.0015	1.372 ± 0.038	0.0090 ± 0.0005	0.229 ± 0.013	Blue-grey
16	0.0650 ± 0.0005	1.651 ± 0.013	0.0470 ± 0.0015	1.194 ± 0.038	0.0090 ± 0.0005	0.229 ± 0.013	White
17	0.0580 ± 0.0005	1.473 ± 0.013	0.0420 ± 0.0015	1.067 ± 0.038	0.0080 ± 0.0005	0.203 ± 0.013	Red-violet
18	0.0500 ± 0.0005	1.270 ± 0.013	0.0330 ± 0.0015	0.838 ± 0.038	0.0085 ± 0.0005	0.216 ± 0.013	Pink
19	0.0420 ± 0.0005	1.067 ± 0.013	0.0270 ± 0.0015	0.686 ± 0.038	0.0075 ± 0.0005	0.191 ± 0.013	Cream
20	0.03575 ± 0.00025	0.9081 ± 0.0064	0.02375 ± 0.00075	0.603 ± 0.019	0.00600 ± 0.00025	0.1524 ± 0.0064	Yellow
21	0.03225 ± 0.00025	0.8192 ± 0.0064	0.02025 ± 0.00075	0.514 ± 0.019	0.00600 ± 0.00025	0.1524 ± 0.0064	Deep green
22	0.02825 ± 0.00025	0.7176 ± 0.0064	0.01625 ± 0.00075	0.413 ± 0.019	0.00600 ± 0.00025	0.1524 ± 0.0064	Black
22s	0.02825 ± 0.00025	0.7176 ± 0.0064	0.00600 ± 0.00075	0.152 ± 0.019	0.01110 ± 0.00025	0.2826 ± 0.0064	(undefined)
23	0.02525 ± 0.00025	0.6414 ± 0.0064	0.01325 ± 0.00075	0.337 ± 0.019	0.00600 ± 0.00025	0.1524 ± 0.0064	Deep blue
24	0.02225 ± 0.00025	0.5652 ± 0.0064	0.01225 ± 0.00075	0.311 ± 0.019	0.00500 ± 0.00025	0.1270 ± 0.0064	Medium purple
25	0.02025 ± 0.00025	0.5144 ± 0.0064	0.01025 ± 0.00075	0.260 ± 0.019	0.00500 ± 0.00025	0.1270 ± 0.0064	Orange
26	0.01825 ± 0.00025	0.4636 ± 0.0064	0.01025 ± 0.00075	0.260 ± 0.019	0.00400 ± 0.00025	0.1016 ± 0.0064	Brown
26s	0.01865 ± 0.00025	0.4737 ± 0.0064	0.00500 ± 0.00075	0.127 ± 0.019	0.00680 ± 0.00025	0.1734 ± 0.0064	(undefined)
27	0.01625 ± 0.00025	0.4128 ± 0.0064	0.00825 ± 0.00075	0.210 ± 0.019	0.00400 ± 0.00025	0.1016 ± 0.0064	Medium grey
28	0.01425 ± 0.00025	0.3620 ± 0.0064	0.00725 ± 0.00075	0.184 ± 0.019	0.00350 ± 0.00025	0.0889 ± 0.0064	Blue-green
29	0.01325 ± 0.00025	0.3366 ± 0.0064	0.00725 ± 0.00075	0.184 ± 0.019	0.00300 ± 0.00025	0.0762 ± 0.0064	Red
30	0.01225 ± 0.00025	0.3112 ± 0.0064	0.00625 ± 0.00075	0.159 ± 0.019	0.00300 ± 0.00025	0.0762 ± 0.0064	Yellow
31	0.01025 ± 0.00025	0.2604 ± 0.0064	0.00525 ± 0.00075	0.133 ± 0.019	0.00250 ± 0.00025	0.0635 ± 0.0064	White
32	0.00925 ± 0.00025	0.2350 ± 0.0064	0.00425 ± 0.00075	0.108 ± 0.019	0.00250 ± 0.00025	0.0635 ± 0.0064	Deep green
33	0.00825 ± 0.00025	0.2096 ± 0.0064	0.00425 ± 0.00075	0.108 ± 0.019	0.00200 ± 0.00025	0.0508 ± 0.0064	Black
34	0.00725 ± 0.00025	0.1842 ± 0.0064	0.00325 ± 0.00075	0.0826 ± 0.019	0.00200 ± 0.00025	0.0508 ± 0.0064	Orange
^^a ^bNot strictly defined, and may vary for a given gauge.

Six hypodermic needles onLuer connectors.These needles are normally used with other medical devices, such as a syringe; from top to bottom:

26G ×1⁄2″ (0.45 × 12 mm) (brown)
25G ×5⁄8″ (0.5 × 16 mm) (orange)
22G ×1+1⁄4″ (0.7 × 30 mm) (black)
21G ×1+1⁄2″ (0.8 × 40 mm) (green)
20G ×1+1⁄2″ (0.9 × 40 mm) (yellow)
19G ×1+1⁄2″ (1.1 × 40 mm) (cream)

Rapidblood transfusionthrough 23G or smaller needles can causehemolysis(rupturing of red blood cells).^[8]

Sizes of catheters

This includesperipheral venous catheters.The gauge compared to outer diameter is the same as for needles, but the color coding is different.

Gauge	Outer diameter (mm)	Maximum flow rate (ml/min)	Color
14	2.0	250–300	Orange
16	1.7	180	Grey
18	1.3	75–120^[9]	Green^[9]
20	1.1	40–80^[9]	Pink^[9]
22	0.9	42-55^[9]	Blue^[9]
24	0.7	20-35^[9]	Yellow^[9]
26	0.6	10-13^[9]	Black^[9]

References

^Page 400in:Steven M. Yentis, Nicholas P. Hirsch, James Ip (2013).Anaesthesia and Intensive Care A-Z E-Book: An Encyclopedia of Principles and Practice. FRCA Study Guides(5 ed.). Elsevier Health Sciences.ISBN 978-0-7020-5375-7.{{cite book}}:CS1 maint: multiple names: authors list (link)
^^a ^bPöll, J. S. (1999)."The story of the gauge".Anaesthesia.54(6):575–581.doi:10.1046/j.1365-2044.1999.00895.x.ISSN 1365-2044.
^"'French', 'gauge' and millimeters ".University of California, San Francisco.Archived fromthe originalon 2017-08-18.Retrieved2018-02-03.
^Machinery's Handbook 27.New York, NY: Industrial Press, Inc. 2004. p. 2520.
^^a ^b"Syringe Needle Gauge Chart".Sigma Aldrich.Retrieved20 March2012.
^"Hypodermic Needle Gauge Chart".Medical Tube Technology, Inc. Archived fromthe originalon 10 October 2004.Retrieved20 March2012.
^"ISO 6009:2016 Hypodermic needles for single use -- Colour coding for identification".International Organization for Standardization.Publication date: 2016-08
^Miller, Michal A.; Schlueter, Annette J. (2004). "Transfusions via hand-held syringes and small-gauge needles as risk factors for hyperkalemia".Transfusion.44(3):373–381.doi:10.1111/j.1537-2995.2004.00653.x.ISSN 0041-1132.PMID 14996194.S2CID 22956171.
^^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^jPage 110in:Edward Doyle (2007).Pediatric Anesthesia.OUP Oxford.ISBN 978-0-19-920279-9.

External links

Iserson KV (1987). "The origins of the gauge system for medical equipment".J Emerg Med.5(1):45–8.doi:10.1016/0736-4679(87)90009-6.PMID 3295010.
Sheet Metal Gauge Size Data – Engineers Edge

[nominal-7] Not strictly defined, and may vary for a given gauge.

[1] Page 400in:Steven M. Yentis, Nicholas P. Hirsch, James Ip (2013).Anaesthesia and Intensive Care A-Z E-Book: An Encyclopedia of Principles and Practice. FRCA Study Guides(5 ed.). Elsevier Health Sciences.ISBN 978-0-7020-5375-7.{{cite book}}:CS1 maint: multiple names: authors list (link)

[:0-2] Pöll, J. S. (1999)."The story of the gauge".Anaesthesia.54(6):575–581.doi:10.1046/j.1365-2044.1999.00895.x.ISSN 1365-2044.

[3] "'French', 'gauge' and millimeters ".University of California, San Francisco.Archived fromthe originalon 2017-08-18.Retrieved2018-02-03.

[MH-4] Machinery's Handbook 27.New York, NY: Industrial Press, Inc. 2004. p. 2520.

[Sigma-5] "Syringe Needle Gauge Chart".Sigma Aldrich.Retrieved20 March2012.

[6] "Hypodermic Needle Gauge Chart".Medical Tube Technology, Inc. Archived fromthe originalon 10 October 2004.Retrieved20 March2012.

[8] "ISO 6009:2016 Hypodermic needles for single use -- Colour coding for identification".International Organization for Standardization.Publication date: 2016-08

[MillerSchlueter2004-9] Miller, Michal A.; Schlueter, Annette J. (2004). "Transfusions via hand-held syringes and small-gauge needles as risk factors for hyperkalemia".Transfusion.44(3):373–381.doi:10.1111/j.1537-2995.2004.00653.x.ISSN 0041-1132.PMID 14996194.S2CID 22956171.

[Doyle-10] ^^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^jPage 110in:Edward Doyle (2007).Pediatric Anesthesia.OUP Oxford.ISBN 978-0-19-920279-9.

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