🪝 Crochet Hook Converter
Convert crochet hook sizes between US, metric and UK
About this calculator
The Crochet Hook Converter translates hook sizes across US letter, metric (mm), and UK numbering systems. Enter a size in any system to get the equivalents — for example a US H-8 is 5.0 mm. International patterns mix conventions freely, and a wrong hook changes your entire project's gauge.
Tip: ergonomic and inline hooks with the same millimeter size can still produce different tension, so swatch with the actual hook you plan to use, not just one with a matching number.