Needle gauge chart

Once you know the number.

Every gauge in the chart, priced and in stock, with no account needed to see what it costs.

Still not sure which one you want?

Three plain questions, no medical words, and the Gauge Finder picks the gauge and the length for you.

The gauges people actually search for

The scale runs backwards, so a higher number is a thinner needle. That is the single most useful thing to know about it and the reason 31G sounds bigger than 18G and is not.

18G and 21G are drawing-up sizes. Wide enough to pull liquid through quickly and far too wide to inject with comfortably. 18G is usually a blunt fill needle, which is blunt on purpose: it cannot core a rubber stopper the way a sharp tip can, and it is not meant to go anywhere near skin.

23G, 25G and 27G are the general injecting range, and this is where most of the searching happens. 23G is the thickest of the three and the fastest to draw through. 25G is the middle, and the one most people land on. 27G is finer and more comfortable and slower to fill. All three are ISO colour coded at the hub, which is why a box of 23G needles has the same blue hub whoever made it.

29G, 30G and 31G are the fine end, almost always on an insulin syringe with the needle fixed to the barrel. The difference between them is comfort against draw time and nothing else. 29G, 30G or 31G: which should I buy? goes through that trade properly.

32G is pen needle territory, 4mm to 8mm, screwed onto an injector pen rather than a syringe.

Length is the other number, and it is a separate decision

Gauge is how thick. Length is how far in, and the two are chosen independently. A 25G needle comes in 16mm, 25mm and 38mm, and those are three different jobs with the same hole.

Which length reaches which layer depends on the medicine and on the person, so it is a question for whoever prescribed it rather than a rule to take off a chart. What the chart can tell you is which lengths exist.