More than twelve conventions exist for numbering the sizes of sewing machine needles, though only two remain in common use: the American (established and propagated by Singer) and the European (also called the "number metric" or "NM"). The European designation, established in 1942, is considered the uniform fixed size and corresponds to the diameter of the needle in hundredths of a millimeter at a non-reinforced point above the scarf. The following chart gives a comparison of the two sizes. In both cases, a larger number corresponds to a larger, heavier needle.
The size of a given needle is often indicated with a pair of these numbers, e.g., "14/90" or "90/14" (the order of the numbers has no significance).
Most currently manufactured needles are designated according to "type", and fall into the following categories:
Intended as an all-purpose needle, preferred for woven fabrics where a sharper needle could ruin the fabric. Similar to a ballpoint needle but tapered to allow the needle to slip through without producing a run.
These needles come with an extra large eye and a specially shaped scarf to prevent embroidery thread from shredding.
Similar to a universal needle but has rounded edges and is not tapered the same way. Intended for closely woven fabrics where the rounded tip will push the weave out of the way rather than cut through it.
Intended for tightly woven cottons such as canvass. Has a strong, sharp point and very slender eye.
Needle has distinct "wings" on either side of the eye which hold the fabric open. Often used on hems and borders, and for decorative finishing. A larger size needle will leave a larger hole in the final piece of sewn fabric.
These have a distinct triangular point to help the needle make a large, clean hole in non-woven materials like vinyl.
Similar to an embroidery needle with a large eye and extra long scarf, but also includes a Teflon coating to the eye so that metallic threads will not shred when used.
Designed with an extra strong shaft and with a tapered point to penetrate multiple layers of woven fabrics without breaking and without shredding either the thread or the fabric being sewn.
These needles can only be used in serger and overlocking machines.
More slender and sharper than the universal needle. Suitable for fine woven fabrics, but also compatible for quilting and appliqué.
These needles are intended for use on fabrics with a significant amount of Spandex or similar fabric content. Rounded tip and specialized scarf and eye to prevent skipping.
These have exceptionally sharp points and a very large eye to accommodate thick decorative topstitching threads. Very similar to the leather needle.
Needles set in pairs or in groups of three on a single shaft designed to sew multiple, usually decorative, threads at once. These require specialized machinery to accommodate the extra needles, as well as multiple thread feeds. The twin or tripple designation is usually accompanied by another needle type specification such as "stretch" or "denim", etc.