What Are the Different Sizes of Crochet Thread?
Crochet thread is usually made in sizes three to 100, with diameter inversely proportional to number. Three is thickest, and the higher the number the thinner the thread. Patterns usually include a recommended size crochet thread. Most patterns in the United States call for size 10, according to thread-maker DMC.
While crochet thread comes in sizes 3, 5, 8, 10, 20, 30, 40 and up, size 10 is the most common. It is known as "bedspread weight," because it is commonly used for bedspreads, tablecloths, place mats, trims and doilies. It's versatile and can be used on large and small projects.
Size 3 crochet thread is the heaviest of all crochet thread. It is nearly as thick as yarn.
Sizes 30 and above
The smaller sizes 30, 40 and up are rarely used, but work well for lacy patterns. Historically, crochet thread came in much finer sizes, down to 200. Threads thinner than size 30 generally need to be mail-ordered.
Size 100 crochet thread is generally the same thickness as sewing thread.
Coasters and baby clothes require a particular size thread, usually the pattern will note the size thread required. Other items like snowflakes, doilies, and crochet-edge baby blankets can be made with whatever size of thread you prefer. Crochet thread comes either in a ball or a skein.
Crochet hooks are also identified by a numbering system--the lower the number, the larger the hook. Lower numbered hooks are usually used with thicker threads. Higher numbered hooks are used with finer threads to create more delicate items, according to DMC. A size 7 or 8 crochet hook is generally used with the classic size 10 thread.