Right up front let’s just get out of the way the fact that there (sadly) is no real industry standard for yarn weights. It's all pretty nebulous... That means the standard titles for yarn weights like "sport" and "dk" aren't concrete definitions. They're just general, fuzzy categories.
Despite their limitations, though, you'll still see those common, ambiguous terms like "fingering" and need to work with them... And they are handy general categories. So, what are the standard terms? Let’s rank them thinnest to thickest for what we carry at Twisted.
Fun Fact Alert! We have our yarns at the store arranged by brand, so if you're shopping for a specific weight you'll need to do some browsing. To help, we have color-coded the signs by weight and added the recommended stitches per inch.
Here's our system:
- Lace: ~8.5 stitches per inch, ~550 yards/3.5 oz
- Fingering: 7-8 stitches per inch, 370-460 yards/3.5 oz
- Sport: 6-7 stitches per inch, 290-360 yards/3.6 oz
- DK: 5.5-6 stitches per inch, 240-280 yards/3.5 oz
- Worsted: 4.75-5.25 stitches per inch, 200-250 yards/3.5 oz
- Aran: 4-4.5 stitches per inch, 170-200 yards/3.5 oz
- Bulky: 2.75-3.75 stitches per inch, 140-170 yards/3.5 oz
- Super Bulky: ~2.5 stitches per inch, ~120 yards/3.5 oz
What is something concrete that you can rely on? Well, for most of us, stitches per inch will be a much more useful way to think of yarn weight than those standard fuzzy titles. 4 stitches per inch is 4 stitches per inch, darn it!
Most yarn labels will have on them what the manufacturer thinks is the best gauge for that yarn. That's just a suggestion, usually a very good one, but you might want it a little tighter or looser to make your ideal fabric for your particular project. For example, Twistedista Carol loves dense fabrics and routinely gets Aran weight yarn to knit sweaters that call for Worsted. She gets gauge but with a thicker yarn so it's a firmer fabric. You can knit nearly any weight yarn to any gauge, but you're less and less likely to like the resulting fabric the farther you get from the sweet spot.
In addition, most yarn labels will list a suggested needle or hook size. That's a lot sketchier because everyone knits and crochets differently and will need to use a different needle or hook to get a certain gauge. So consider those suggested needle sizes with a big ol' grain o' salt.
You may also see reference to the Yarn Council of America weights and wraps per inch. These are less used, but can still come up. The YCA terms in particular aren't common. Wraps per inch is a good way to specifically examine how thick yarn is by wrapping a strand around a cylinder and seeing how it measures up.
Most yarn labels will give you a recommended gauge for that yarn. And, similarly, every pattern should have a recommended gauge. Match those two up and that is where you can start in figuring out if the yarn in your hand will work for the pattern you want to use! Remember, you can knit and crochet with anything but the thickness of the yarn and the size of the needle or hook will determine what the finished look of your project...