When selecting a needle gauge it is important to keep in mind the volume of the syringe and the dead volume of the needle. For example, it will be very difficult to prime a 10 µL syringe if the dead volume in the needle is greater than 10 µL. Refer to the needle gauge index to choose a needle gauge with an appropriate µL/inch before selecting a needle. Select the minimum length that allows you to carry out your application comfortably.

Note: The ‘s’ on a 22s needle represents a smaller I.D. (inner diameter) for the needle and a thicker needle wall for better durability. For example, a 26 gauge needle has an O.D. (outer diameter) of 0.46 mm and an I.D. of 0.26 mm while the 26s gauge needle has an O.D. of 0.47 mm and an I.D. of 0.13 mm. The 26s has half the I.D. of the 26 gauge needle. Also, the difference in the wall thickness nearly doubles with 26s gauge having a thickness of 0.18 mm while the 26 gauge is only 0.10 mm.

Hamilton Needles

Gauge
Needle Nominal O.D.
(mm)
Needle Nominal I.D.
(mm)
Needle Wall Thickness
(mm)
Needle Dead Volume
(µL/25.4 mm)
34 gauge needle 0.159 0.051 0.051 0.052 µL/25.4 mm
33 gauge needle 0.21 0.108 0.051 0.233 µL/25.4 mm
32 gauge needle
0.235 0.108 0.064 0.233 µL/25.4 mm
31 gauge needle 0.261 0.133 0.064 0.353 µL/25.4 mm
30 gauge needle 0.312 0.159 0.076 0.504 µL/25.4 mm
29 gauge needle 0.337 0.184 0.076 0.675 µL/25.4mm
28 gauge needle 0.362 0.184 0.089 0.675 µL/25.4 mm
27 gauge needle 0.413 0.21 0.102 0.876 µL/25.4 mm
26s gauge needle 0.474 0.127 0.178 0.322 µL/25.4 mm
26 gauge needle 0.464 0.26 0.102 1.349 µL/25.4 mm
25s gauge needle 0.515 0.153 0.178 0.464 µL/25.4 mm
25 gauge needle 0.515 0.26 0.127 1.349 µL/25.4 mm
24 gauge needle 0.566 0.311 0.127 1.93 µL/25.4 mm
23s gauge needle 0.642 0.116 0.267 0.268 µL/25.4 mm
23 gauge needle 0.642 0.337 0.152 2.266 µL/25.4 mm
22s gauge needle 0.718 0.168 0.279 0.563 µL/25.4 mm
22 gauge needle 0.718 0.413 0.152 3.403 µL/25.4 mm
21 gauge needle 0.819 0.514 0.152 5.271 µL/25.4 mm
20 gauge needle 0.908 0.603 0.152 7.255 µL/25.4 mm
19 gauge needle 1.067 0.686 0.191 9.389 µL/25.4 mm
18 gauge needle 1.27 0.838 0.216 14.011 µL/25.4 mm
17 gauge needle 1.473 1.067 0.203 22.715 µL/25.4 mm
16 gauge needle 1.651 1.194 0.229 28.444 µL/25.4 mm
15 gauge needle 1.829 1.372 0.229 37.529 µL/25.4 mm
14 gauge needle 2.109 1.6 0.254 51.076 µL/25.4 mm
13 gauge needle 2.413 1.804 0.305 64.895 µL/25.4 mm
12 gauge needle 2.769 2.159 0.305 93 µL/25.4 mm
11 gauge needle 3.048 2.388 0.33 113.728 µL/25.4 mm
10 gauge needle 3.404 2.693 0.356 144.641 µL/25.4 mm
*mm are nominal