Needle gauge size chart
Each gauge has a fixed outer diameter range. Inner diameter varies by wall class (RW, TW, ETW, UTW). ISO 6009 colours repeat across gauges (e.g., orange at 34G and 25G).
Both tables below are compiled gauge by gauge from three sources: ISO 9626:2016 for the tubing dimensions, ISO 6009:2016 for the colour code, and Nipro's data sheet for the lengths and wall classes actually supplied. No one of them publishes this arrangement.
Diameter and colour code by gauge
| Gauge | ISO metric size (mm) | OD min (mm) | OD max (mm) | ISO 6009 colour |
|---|---|---|---|---|
| 34 | 0.18 | 0.178 | 0.191 | Orange |
| 33 | 0.20 | 0.203 | 0.216 | Black |
| 32 | 0.23 | 0.229 | 0.241 | Deep green |
| 31 | 0.25 | 0.254 | 0.267 | White |
| 30 | 0.30 | 0.298 | 0.320 | Yellow |
| 29 | 0.33 | 0.324 | 0.351 | Red |
| 28 | 0.36 | 0.349 | 0.370 | Blue-green |
| 27 | 0.40 | 0.400 | 0.420 | Medium grey |
| 26 | 0.45 | 0.440 | 0.470 | Brown |
| 25 | 0.50 | 0.500 | 0.530 | Orange |
| 24 | 0.55 | 0.550 | 0.580 | Medium purple |
| 23 | 0.60 | 0.600 | 0.673 | Deep blue |
| 22 | 0.70 | 0.698 | 0.730 | Black |
| 21 | 0.80 | 0.800 | 0.830 | Deep green |
| 20 | 0.90 | 0.860 | 0.920 | Yellow |
| 19 | 1.10 | 1.030 | 1.100 | Cream |
| 18 | 1.20 | 1.200 | 1.300 | Pink |
| 17 | 1.40 | 1.400 | 1.510 | Red-violet |
| 16 | 1.60 | 1.600 | 1.690 | White |
| 15 | 1.80 | 1.750 | 1.900 | Blue-grey |
| 14 | 2.10 | 1.950 | 2.150 | Pale green |
| 13 | 2.40 | 2.300 | 2.500 | Purple |
| 12 | 2.70 | 2.650 | 2.850 | Pale blue |
| 11 | 3.00 | 2.950 | 3.150 | Green-yellow |
| 10 | 3.40 | 3.300 | 3.500 | Olive brown |
34G – 25Gfull width = 0.50 mm
- 34G0.18 mm
- 33G0.20 mm
- 32G0.23 mm
- 31G0.25 mm
- 30G0.30 mm
- 29G0.33 mm
- 28G0.36 mm
- 27G0.40 mm
- 26G0.45 mm
- 25G0.50 mm
25G – 10Gfull width = 3.40 mm
- 25G0.50 mm
- 24G0.55 mm
- 23G0.60 mm
- 22G0.70 mm
- 21G0.80 mm
- 20G0.90 mm
- 19G1.10 mm
- 18G1.20 mm
- 17G1.40 mm
- 16G1.60 mm
- 15G1.80 mm
- 14G2.10 mm
- 13G2.40 mm
- 12G2.70 mm
- 11G3.00 mm
- 10G3.40 mm
Minimum bore and supplied lengths by gauge
| Gauge | RW ID min (mm) | TW ID min (mm) | ETW ID min (mm) | UTW ID min (mm) | Nipro supplied lengths | Nipro wall class |
|---|---|---|---|---|---|---|
| 34 | 0.064 | 0.091 | 0.105 | — | — | — |
| 33 | 0.089 | 0.105 | 0.125 | — | — | — |
| 32 | 0.089 | 0.105 | 0.125 | 0.146 | — | — |
| 31 | 0.114 | 0.125 | 0.146 | 0.176 | — | — |
| 30 | 0.133 | 0.165 | 0.190 | 0.240 | 1/2" (13 mm) | TW |
| 29 | 0.133 | 0.190 | 0.240 | 0.265 | 1/2" (13 mm) | RW |
| 28 | 0.133 | 0.190 | — | — | — | — |
| 27 | 0.184 | 0.241 | — | — | 1/2" (13 mm), 3/4" (19 mm), 1 1/4" (32 mm), 1 1/2" (40 mm) | RW |
| 26 | 0.232 | 0.292 | — | — | 1/2" (13 mm), 7/8" (22 mm) | RW |
| 25 | 0.232 | 0.292 | — | — | 1/2" (13 mm), 5/8" (16 mm), 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (38 mm) | TW |
| 24 | 0.280 | 0.343 | — | — | 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (38 mm) | TW |
| 23 | 0.317 | 0.370 | 0.460 | — | 5/8" (16 mm), 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (38 mm) | TW |
| 22 | 0.390 | 0.440 | 0.522 | — | 5/8" (16 mm), 3/4" (19 mm), 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (40 mm), 2" (50 mm) | TW |
| 21 | 0.490 | 0.547 | 0.610 | 0.645 | 5/8" (16 mm), 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (40 mm), 2" (50 mm), 2 3/4" (70 mm) | TW |
| 20 | 0.560 | 0.635 | 0.687 | 0.713 | 1" (25 mm), 1 1/2" (40 mm), 2" (50 mm), 2 3/4" (70 mm) | TW |
| 19 | 0.648 | 0.750 | 0.850 | 0.891 | 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (40 mm), 2" (50 mm) | TW |
| 18 | 0.790 | 0.910 | 1.041 | — | 1" (25 mm), 1 1/4" (32 mm), 1 1/2" (40 mm), 2" (50 mm) | TW |
| 17 | 0.950 | 1.156 | 1.244 | 1.276 | — | — |
| 16 | 1.100 | 1.283 | 1.390 | — | 1" (25 mm), 1 1/2" (40 mm) | TW |
| 15 | 1.300 | 1.460 | 1.560 | — | — | — |
| 14 | 1.500 | 1.600 | 1.727 | — | — | — |
| 13 | 1.700 | 1.956 | — | — | — | — |
| 12 | 1.950 | 2.235 | — | — | — | — |
| 11 | 2.200 | 2.464 | — | — | — | — |
| 10 | 2.500 | 2.819 | — | — | — | — |
What the columns mean
Gauge number and outer diameter move in opposite directions. A 34G tube has an OD between 0.178 and 0.191 mm, while a 10G tube runs 3.300–3.500 mm. The designated metric size is ISO's size label for the gauge, not a nominal with a tolerance either side: the standard sets a separate minimum and maximum, and the label does not always fall between them. A 33G tube is labelled 0.20 mm and must measure 0.203–0.216 mm.
Inner diameter is not fixed by gauge. ISO 9626 defines minimum ID for each wall class — Regular (RW), Thin (TW), Extra Thin (ETW), Ultra Thin (UTW) — at the same OD. At 25G, the RW minimum ID is 0.232 mm and the TW minimum is 0.292 mm. At 21G, the four classes step from 0.490 mm (RW) to 0.645 mm (UTW). The standard does not specify a maximum ID. Tabulated values are lower bounds, not nominals.
ISO 6009 assigns a colour to each metric size, and says outright that it "does not specify that needles are to be colour-coded or to what portion of the needle and/or packaging the colour is to be applied" — placement belongs to product standards such as ISO 7864. The code is not reversible either: orange is both 34G and 25G, black 33G and 22G, deep green 32G and 21G, yellow 30G and 20G, white 31G and 16G. A hub colour alone identifies neither the gauge nor the diameter.
Nipro’s product range shows which lengths actually ship at each gauge. Lengths are listed in inches with the manufacturer’s rounded millimetre equivalents. At some gauges, 1 1/2" appears as 40 mm, and at others as 38 mm. This inconsistency is reproduced from Nipro’s data sheet. Nipro lists 29G OD as 0.34 mm, whereas ISO 9626 places 29G at 0.33 mm metric size with an OD band of 0.324–0.351 mm. The Nipro value falls inside the ISO band. The ISO figure is preferred for dimensional reference.
American Tube Technology publishes a separate imperial tubing table. It lists nominal OD, wall thickness, and ID in inches. This is not a conversion of the ISO metric figures. Component Supply publishes its own hub colours for blunt dispensing needles, and they contradict ISO 6009 — 25G is red there, orange in the standard. Component Supply states that ISO 6009 covers single-use hypodermic needles in the medical device industry and does not necessarily apply to industrial, laboratory or medical dispensing needles. The two systems are not interchangeable.
Every row in both tables is a measurement, not a part: the 25 G rows give an outer-diameter range, minimum bores by wall class, a colour and the lengths Nipro supplies at that gauge — but no catalogue number, so a retail listing has nothing here to match against. A search of Amazon on 2026-08-01 for Nipro hypodermic needles at 25 G × 1″, one of those supplied lengths, returned ten listings and not one was Nipro-branded: unbranded industrial dispensing needles stating neither the ISO 9626 diameter band the row publishes nor a wall class. Nothing retrieved could be shown to match a row, so nothing is linked.
Sources
- ISO 9626:2016 — Stainless steel needle tubing for the manufacture of medical devices (International Organization for Standardization)
- American Tube Technology — Hypodermic stainless steel tubing size gauge chart (American Tube Technology)
- ISO 6009:2016 — Hypodermic needles for single use, colour coding for identification (International Organization for Standardization)
- Nipro Medical Europe — Hypodermic Needles for Injection Therapy, product data sheet (Nov 2019) (Nipro Medical Europe)
- Component Supply — Needle hub colours and gauge sizes (dispensing/industrial system) (Component Supply Company)
Specifications last verified: