Crochet Hook Sizes — Complete Conversion Chart
Hook size by yarn weight, US letter to metric millimetres, UK conversion, and when to size up or down.
Crochet hooks are sized by diameter in millimetres — from 0.6mm (thread crochet) up to 25mm (jumbo). The most common general-purpose hooks are 5mm (US H/8) for worsted yarn and 4mm (US G/6) for DK yarn. Pattern designers list both metric and US-letter sizes; the metric measurement is more precise. To make amigurumi tighter, size down from the yarn's recommended hook by half a millimetre. To make a blanket drapier, size up by half a millimetre.
| Metric (mm) | US letter | UK | Best yarn weight | Common use |
|---|---|---|---|---|
| 2.25mm | B/1 | 13 | Lace / Crochet thread | Doilies, fine lace |
| 2.75mm | C/2 | 12 | Lace / Sock | Detailed lace, fine motifs |
| 3.25mm | D/3 | 10 | Sock / Fingering | Lightweight shawls, socks |
| 3.5mm | E/4 | 9 | Sport / DK | Baby items, fine amigurumi |
| 3.75mm | F/5 | 9 | DK / Light Worsted | Garments, blankets in DK |
| 4mm | G/6 | 8 | DK / Light Worsted | Standard DK projects |
| 4.5mm | 7 | 7 | DK / Worsted | Tight worsted, loose DK |
| 5mm | H/8 | 6 | Worsted | Most common — amigurumi, blankets |
| 5.5mm | I/9 | 5 | Worsted / Aran | Aran-weight projects, drapier worsted |
| 6mm | J/10 | 4 | Aran / Bulky | Heavy garments, throws |
| 6.5mm | K/10½ | 3 | Bulky | Quick-make blankets |
| 8mm | L/11 | 0 | Super Bulky | Chunky throws, baskets |
| 9mm | M/13 | 00 | Super Bulky | Statement pieces |
| 10mm | N/15 | 000 | Jumbo / Roving | Oversized accents |
| 15mm+ | P/Q/S | — | Jumbo | Arm-crochet rugs |
How to pick the right hook
Start with the size on the yarn's ball band — that's the gauge the manufacturer tested. Then check the pattern's recommended hook. If your pattern wants a tighter fabric than the ball band suggests (typical for amigurumi so stuffing doesn't show through), size down by 0.5mm. If you want drapier fabric (blankets, lightweight garments), size up by 0.5mm.
Why metric beats US letters
The US letter system is inconsistent across hook brands — one brand's J/10 might be 6.0mm, another's 6.5mm. Metric millimetres are an exact measurement everyone agrees on. When buying online or following an international pattern, always reference the millimetre size first.
Hook material — does it matter?
Aluminium is the standard — affordable, durable, slightly slick. Bamboo and wood are warmer in the hand and grip yarn slightly more, useful for slippery cotton. Ergonomic hooks with cushioned handles reduce hand fatigue on long projects — worth the upgrade once you're crocheting weekly.
Common questions
What size crochet hook for beginners?
5mm (US H/8) with worsted-weight yarn is the standard beginner combination. It's large enough to see your stitches clearly, and worsted is forgiving.
What hook size for amigurumi?
Most amigurumi patterns use 4mm or 4.5mm hook with worsted-weight yarn — that's one or half a size smaller than worsted's normal pairing, so the fabric is tight enough that polyfill stuffing doesn't show through.
What is a US H crochet hook in mm?
US H = 5mm. Sometimes labelled H/8.
What is a 4mm crochet hook in US letter?
4mm = US G or G/6.
Should I size up or down on hook?
Size down for amigurumi (tighter fabric, no stuffing showing). Size up for blankets/wearables when you want more drape. Always swatch and check gauge before committing.
Do hook brands measure the same?
Metric millimetres are consistent. US letter sizes drift — one brand's J/10 might be 6.0mm, another's 6.5mm. Trust the millimetre number.
Patterns to make
Free patterns that put this guide to work: