A 3.5mm crochet hook is a US E-4. In UK sizing it’s a 9. Use the mm number as your main reference for this size, since letter labeling is where most of the confusion happens between brands.
3.5mm to US letter, UK, and yarn weight
A 3.5mm crochet hook is a US E-4. In UK sizing it’s a 9. It’s typically used for DK weight yarn; check the mm stamp on the hook itself whenever a pattern’s letter doesn’t match what you expect.
What projects use a 3.5mm hook
Match DK weight yarn to this hook for the gauge most patterns expect, then adjust up or down a size if your own tension runs tight or loose. Swatch first for anything that needs to fit.
Frequently asked questions
Is 3.5mm the same as E-4?
A 3.5mm crochet hook is a US E-4. In UK sizing it’s a 9.
What size yarn goes with a 3.5mm hook?
Dk weight yarn is the usual match for this size.
See the full hook size chart
Compare 3.5mm against every other mm, US, and UK size in one table.