When working in microfluidics, selecting the correct hypodermic needle gauge is crucial for ensuring a secure and efficient connection between syringes and soft-walled tubing. Hypodermic needles are commonly used in these setups to facilitate the smooth transfer of fluids, and choosing the right gauge can prevent leaks, enhance flow precision, and ensure compatibility with tubing diameters.
In this post, you’ll find a needle size tool and a comprehensive chart listing the inner and outer diameters of various needle gauges in both ‘mm’ and ‘inch’. These can be a handy reference when determining the best needle to match the inner diameter of your soft-walled tubing.
🔎 Example: a 23G needle has an outer diameter of 0.02525 inch (0.6414 mm) and an inner diameter of 0.01325 inch (0.337 mm).
🚨 Note: the “s” in needle gauges like 22s and 26s indicates a smaller inner diameter and a thicker wall compared to the standard 22 and 26 gauges respectively. This enhanced wall thickness improves needle durability.
💡Tip: always use a needle with a larger outer diameter than the inner diameter of your tubing!
🚀 Explore the tool and chart below to find the right needle gauge for your microfluidic setup, and take the guesswork out of achieving optimal fluid connections.
Needle Gauge Size Chart
| Needle gauge | Outer diameter (inches) | Outer diameter (mm) | Inner diameter (inches) | Inner diameter (mm) |
| 7 | 0.180 | 4.572 | 0.150 | 3.810 |
| 8 | 0.165 | 4.191 | 0.135 | 3.429 |
| 9 | 0.148 | 3.759 | 0.118 | 2.997 |
| 10 | 0.134 | 3.404 | 0.106 | 2.692 |
| 11 | 0.120 | 3.048 | 0.094 | 2.388 |
| 12 | 0.109 | 2.769 | 0.085 | 2.159 |
| 13 | 0.095 | 2.413 | 0.071 | 1.803 |
| 14 | 0.083 | 2.108 | 0.063 | 1.600 |
| 15 | 0.072 | 1.829 | 0.054 | 1.372 |
| 16 | 0.065 | 1.651 | 0.047 | 1.194 |
| 17 | 0.058 | 1.473 | 0.042 | 1.067 |
| 18 | 0.050 | 1.270 | 0.033 | 0.838 |
| 19 | 0.042 | 1.067 | 0.027 | 0.686 |
| 20 | 0.03575 | 0.9081 | 0.02375 | 0.603 |
| 21 | 0.03225 | 0.8192 | 0.02025 | 0.514 |
| 22 | 0.02825 | 0.7176 | 0.01625 | 0.413 |
| 22s | 0.02825 | 0.7176 | 0.006 | 0.152 |
| 23 | 0.02525 | 0.6414 | 0.01325 | 0.337 |
| 24 | 0.02225 | 0.5652 | 0.01225 | 0.311 |
| 25 | 0.02025 | 0.5144 | 0.01025 | 0.260 |
| 26 | 0.01825 | 0.4636 | 0.01025 | 0.260 |
| 26s | 0.01865 | 0.4737 | 0.005 | 0.127 |
| 27 | 0.01625 | 0.4128 | 0.00825 | 0.210 |
| 28 | 0.01425 | 0.3620 | 0.00725 | 0.184 |
| 29 | 0.01325 | 0.3366 | 0.00725 | 0.184 |
| 30 | 0.01225 | 0.3112 | 0.00625 | 0.159 |
| 31 | 0.01025 | 0.2604 | 0.00525 | 0.133 |
| 32 | 0.00925 | 0.2350 | 0.00425 | 0.108 |
| 33 | 0.00825 | 0.2096 | 0.00425 | 0.108 |
| 34 | 0.00725 | 0.1842 | 0.00325 | 0.0826 |
