An H crochet hook, also written H-8, is 5.0mm. This is the letter I get asked about most, since it’s the size most beginner patterns default to for worsted weight yarn.
H hook in mm, and what it’s used for
At 5.0mm, an H hook matches worsted weight yarn, the most widely available weight for blankets, hats, and amigurumi. In UK and Canadian sizing, the same hook is a 6, and I always convert by mm rather than assume a UK number lines up with a US letter.
How H compares to G and I
A G hook (4.0mm) sits one full step smaller, producing a tighter fabric in the same yarn, which I reach for when a toy needs to hold stuffing without gaps. An I hook (5.5mm) goes one step larger, giving a looser drape better suited to garments than dense stitching.
Frequently asked questions
Is H-8 the same as 5mm?
Yes, H and H-8 both refer to the same 5.0mm hook in US sizing.
What yarn weight is an H hook for?
Worsted weight yarn is the standard match for an H hook, making it one of the most commonly used sizes overall.
See the full hook size chart
Compare H against every other letter, mm, and UK size in one table.