How to use the needle gauge converter
- Select whether you are entering a gauge, millimeters, or inches.
- Type the value you have, such as 22, 0.718 mm, or 0.0283 in.
- Read the approximate outside diameter and closest common gauge match.
Needle Gauge to mm Converter
Convert hypodermic needle gauge sizes to approximate outside diameter in millimeters and inches, then compare nearby gauges and common hub colors.
Convert a needle gauge
Choose a gauge or enter a diameter to find the closest common hypodermic needle size.
Approximate outside diameter
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Needle gauge—
Common hub color—
Nearby sizes—
Enter a gauge or diameter to see the conversion.
Common needle gauge chart
Use this quick chart for common hypodermic needle outside diameters. The inner bore can be different for regular-wall, thin-wall, and extra-thin-wall needles.
| Gauge | OD mm | OD inch | Common color |
|---|
Important sizing note
This converter is for quick size reference, supply comparison, lab planning, crafts, and catalog lookup. Needle choice for medical, veterinary, or injection use depends on the medication, patient, route, local guidance, and product labeling.
Needle gauge FAQ
What size is a 25G needle in mm?
A 25 gauge hypodermic needle has an approximate outside diameter of 0.515 mm, or 0.0203 inches.
What is the difference between OD and ID?
OD means outside diameter. ID means inside diameter, or bore. Two needles with the same gauge can have different IDs if the wall thickness is different.
Can I convert mm back to gauge?
Yes. Enter a millimeter value and the tool returns the closest common gauge, plus the neighboring gauge sizes for comparison.