A US size 8 crochet hook is 8mm, also written L-11. Always check this against the mm stamp on the hook itself, since plain-number US sizing is one of the more confusing parts of the whole system.
Size 8 in mm, and what it’s used for
A US size 8 crochet hook is 8mm, also written L-11. It typically pairs with bulky weight yarn; treat the mm number as the tiebreaker whenever a pattern is ambiguous.
Why plain numbers cause confusion
US hook sizing mixes letters and numbers depending on the size, so “size 8” alone is ambiguous unless you know whether it refers to the lettered sequence or a separate numbered one. I recommend always looking for the mm measurement when a pattern only lists a bare number.
Frequently asked questions
What mm is a size 8 crochet hook?
A US size 8 crochet hook is 8mm, also written L-11.
What yarn weight uses this size?
Bulky weight yarn is the usual match for this size.