What size yarn do you use with a H hook?

For a size H (5.0 mm) crochet hook, you typically use worsted weight yarn, which is classified as a medium weight (Category 4). This yarn is versatile and works well for a variety of projects, including blankets, garments, and accessories. You can also use lighter yarns like DK (double knit) or sport weight for more delicate projects, but always check the pattern for specific recommendations.