33-40 sts = 4" st st US 000-1 (1.5-2.25mm) needle
Lace weight is the thinnest, lightest type of yarn. It’s used mostly to knit lace shawls and scarves. To get the open lace effect, use a larger needle size.
23-26 = 4" in st st US 3-5 (3.25-3.75mm) needle
Fine yarn includes sport and baby weight yarn. This is a versatile yarn that’s great for just about anything: cardigans, sweaters, hats, socks, you name it.
21-24 sts = 4" in st st US 5-7 (3.75-4.5mm) needle
DK weight and light worsted yarns fall into this category. These yarns are just a slightly thicker than fine yarns and a slightly thinner than medium yarns.
12-15 sts = 4" in st st US 9-11 (5.5 - 8mm) needle
Chunky yarns and rug yarns fall into this category. These knit up nice and quick and are perfect for warm hats, dramatic scarves, blankets and rugs.
6-11 sts = 4" in st st US 13+ (8mm +) needles
Super bulky yarns are the ultimate in instant gratification. At 6-11 stitches to four inches, you can easily finish a hat in just a few hours. These yarns are usually single ply and super warm on account of their bulk.