Convert crochet hook sizes between metric, US and UK — and browse the full chart.
| Metric (mm) | US | UK / Old UK |
|---|
Steel hooks (used for thread/lace crochet) use reversed numbering — a US steel 00 (3.5mm) is much larger than a US steel 14 (0.75mm).
Crochet hooks are sized differently depending on where the pattern was written. US patterns typically use a letter-number combination (like "H-8"), UK and Australian patterns use a plain number that goes down as the hook gets bigger, and most of the world uses the metric millimeter size stamped right on the hook. When following a pattern from another region, always check the mm size first — it's the one measurement that's consistent everywhere.
Why do US and UK crochet hook sizes use different numbers?
US hook sizes use a letter-number combination while UK (and old UK) sizes use a descending number scale, both dating back to different historical wire-gauge standards. Metric millimeter sizing is the one measurement that means the same thing everywhere.
Is a UK size 8 hook the same in every brand?
Not always exactly, since manufacturers vary slightly. When in doubt, go by the millimeter (mm) measurement stamped on the hook — it's the most reliable way to match sizes across brands and countries.
What is a steel crochet hook?
Steel hooks are thinner hooks used for thread and lace crochet. Confusingly, they use reversed numbering — a US steel size 00 is much larger than a US steel size 14.