0—Lace (Fingering, Size 10 Crochet Thread) Lace yarn or thread is very thin and often used to give a lacy appearance to shawls and doilies.
1—Super Fine (Sock, Fingering, Baby) Super fine yarn is lightweight and typically used for baby items, sock patterns, or shawls. Lacy items often fall under this category, as this type of yarn works best for creating delicate pieces.
2—Fine (Sport, Baby) Sport weight yarn works best for items such as socks, wraps, heirloom sweaters, and other delicate accessories. It is also used for lightweight afghans.
3—Light (DK, Light Worsted) Slightly heavier than a fine weight yarn, this weight is used for items such as garments and heavier baby items.
4—Medium (Worsted, Afghan, Aran) Worsted weight yarn is the most frequently used. It is easy to work with (making it great for beginners), approximately double the weight of DK or sport yarn, and ideal for working up afghans.
5—Bulky (Chunky, Craft, Rug) Bulky yarn is about twice as thick as worsted weight. It usually works up quickly when using large needles/hooks, and it’s great to use when making sweaters, scarves, rugs, and throws.
6—Super Bulky (Roving) Super bulky yarn is a thick yarn that works up quickly. It is most commonly used for cowls, scarves, and hats.
7—Jumbo (Roving) Jumbo yarn is the thickest yarn weight, added in 2014 to classify the super thick yarns that began to appear on the market. Jumbo yarns are great for arm knitting and work up quickly.
The wonderful thing about yarn weights is that they allow you to customize your projects. If your pattern calls for a specific yarn but you prefer another brand, fiber content, or color, you can substitute another yarn of the same weight. You can even change the look of your project by using a different yarn weight to suit your style. Just make sure you take the time to create a gauge swatch following the pattern to see how the stitches will look in the different weight and to ensure the project will turn out the size you want.