Standard Yarn Weight Systems

This is a great chart to answer any yarn/hook questions!  For more info and a printable copy see the Craft Yarn Council Page here

Categories of yarn, gauge ranges, and recommended needle and hook sizes

Yarn Weight Symbol & Category Names
Type of Yarns in Category	Fingering 10-count crochet thread	Sock, Fingering, Baby	Sport, Baby	DK, Light Worsted	Worsted, Afghan, Aran	Chunky, Craft, Rug	Super Bulky, Roving	Jumbo, Roving
Knit Gauge Range* in Stockinette Stitch to 4 inches	33–40** sts	27–32 sts	23–26 sts	21–24 sts	16–20 sts	12–15 sts	7–11 sts	6 sts and fewer
Recommended Needle in Metric Size Range	1.5–2.25 mm	2.25— 3.25 mm	3.25— 3.75 mm	3.75— 4.5 mm	4.5— 5.5 mm	5.5— 8 mm	8— 12.75 mm	12.75 mm and larger
Recommended Needle U.S. Size Range	000–1	1 to 3	3 to 5	5 to 7	7 to 9	9 to 11	11 to 17	17 and larger
Crochet Gauge* Ranges in Single Crochet to 4 inch	32–42 double crochets**	21–32 sts	16–20 sts	12–17 sts	11–14 sts	8–11 sts	7–9 sts	6 sts and fewer
Recommended Hook in Metric Size Range	Steel*** 1.6–1.4 mm Regular hook 2.25 mm	2.25— 3.5 mm	3.5— 4.5 mm	4.5— 5.5 mm	5.5— 6.5 mm	6.5— 9 mm	9— 15 mm	15 mm and larger
Recommended Hook U.S. Size Range	Steel*** 6, 7, 8 Regular hook B–1	B–1 to E–4	E–4 to 7	7 to I–9	I–9 to K–10 1⁄2	K–10 1⁄2 to M–13	M–13 to Q	Q and larger
* GUIDELINES ONLY: The above reflect the most commonly used gauges and needle or hook sizes for specific yarn categories. ** Lace weight yarns are usually knitted or crocheted on larger needles and hooks to create lacy, openwork patterns. Accordingly, a gauge range is difficult to determine. Always follow the gauge stated in your pattern. *** Steel crochet hooks are sized differently from regular hooks—the higher the number, the smaller the hook, which is the reverse of regular hook sizing