Crochet Hook Size Converter

Crochet Hook Size Converter

Converts crochet hook sizes between US letter/number sizing, UK/Canadian sizes, and metric millimeter sizes. Different regions use different sizing systems, making pattern conversion necessary.

Hook size conversion table

Choosing the right hook size

Hook size determines the gauge (stitches per 10 cm). Always work a tension swatch before starting a project. If your swatch has too many stitches, go up a hook size; if too few, go down. The hook size printed on a pattern is a starting recommendation, not a fixed rule, gauge matters more.

Hook materials

• Aluminum: most common, smooth and durable
• Steel: for very fine thread crochet (lace, doilies)
• Bamboo / wood: warmer feel, slight grip; popular for slippery yarns
• Ergonomic: soft handle to reduce hand fatigue in long sessions

UK patterns and vintage sizing

UK crochet patterns use the same UK/Canada sizing system as knitting needles, which counts downward. This creates confusion when following vintage UK patterns:

• Modern UK and European patterns: almost always use metric (mm) , this is the safe, unambiguous size to use. UK crochet magazines (Simply Crochet, Inside Crochet) specify mm sizes.
• Vintage UK patterns (1960s-1990s): may list UK hook numbers (UK 9 = 3.5 mm, UK 7 = 4.5 mm, UK 6 = 5.0 mm). These are the same descending-scale numbers as knitting needles. Always convert to mm before buying a hook.
• US vs UK letter hooks: US "G/6" (4.0 mm) is not UK "6" (5.0 mm). The letter-number US system and the number-only UK system are completely different. When a pattern says "size 6 hook" without specifying metric, check the country of origin.
• Steel hooks for lace (thread crochet): use a different numbering system where higher numbers = thinner hooks (opposite of regular hooks). A US Steel 6 = 1.8 mm; a US Steel 1 = 2.35 mm.