Yarn guide · Charts & reference
Crochet Hook Size Chart: Metric, US & UK
Convert crochet hook sizes between millimeters, US letters and old UK numbers, and learn how to choose the right hook for your yarn and project.
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Crochet hooks are sized by the diameter of their shaft. Metric (millimeter) sizes are used worldwide, US hooks add a letter and number, and some older UK and Canadian hooks use a separate number system. This chart lines them up.
| Metric | US size | Old UK / Canadian |
|---|---|---|
| 2.25 mm | B-1 | 13 |
| 2.75 mm | C-2 | — |
| 3.25 mm | D-3 | 10 |
| 3.5 mm | E-4 | 9 |
| 3.75 mm | F-5 | — |
| 4 mm | G-6 | 8 |
| 4.5 mm | 7 | 7 |
| 5 mm | H-8 | 6 |
| 5.5 mm | I-9 | 5 |
| 6 mm | J-10 | 4 |
| 6.5 mm | K-10½ | 3 |
| 7 mm | — | 2 |
| 8 mm | L-11 | 0 |
| 9 mm | M/N-13 | 00 |
| 10 mm | N/P-15 | 000 |
| 11.5 mm | P-16 | — |
| 15 mm | P/Q | — |
| 16 mm | Q | — |
| 19 mm | S | — |
Why the millimeter size matters
The millimeter measurement is the actual size of the hook, so it is consistent between brands and countries. When a pattern gives both a letter and a millimeter size, always go by the millimeters.
Choosing a hook for your yarn
Start with the hook size recommended on the yarn label, then adjust:
- For amigurumi, use a noticeably smaller hook so the stitches are tight enough to hide the stuffing — with worsted-weight yarn, a 3.5–4 mm hook is common.
- For drapey shawls and garments, go up a size for a softer, more open fabric.
- To match a pattern’s gauge, change hook size — not tension — until your swatch matches.
The yarn weight chart lists typical hook ranges for each yarn weight.
Steel hooks for thread
Very small hooks for crochet thread are often called steel hooks and use their own numbering system, where larger numbers mean smaller hooks. As with regular hooks, check the millimeter size to be sure.
Hook shapes and handles
Hooks differ in the shape of the head and throat. Inline hooks have a head in line with the shaft and a sharply cut throat, while tapered hooks have a rounder head and a throat that narrows more gradually. Neither is better — they simply feel different, so try a few if you can. Ergonomic or cushioned handles can make long sessions more comfortable, especially if your hands tire easily.
When to change hook size
If your gauge swatch has more stitches than the pattern, your stitches are too small — use a larger hook. If it has fewer stitches, use a smaller hook.
Gauge CalculatorCompare your gauge with a pattern’s and see how it will change the finished size.Sources
- Craft Yarn Council, hook and needle size standards — the metric and US crochet hook size equivalents used in this chart.
- Old UK and Canadian hook numbers vary between published charts. Where sources disagree, this chart shows “—” rather than guessing.
Common questions
Does hook size change the size of my stitches?
Yes. A larger hook makes bigger, looser stitches and a larger finished piece; a smaller hook makes tighter stitches and a smaller piece.
What hook should a beginner buy?
A 5 mm (US H-8) hook is a comfortable size for learning with worsted-weight yarn.
Why doesn’t my hook match the letter in the chart?
Letter sizes vary a little between brands. Check the millimeter size printed on the hook — that is the measurement to trust.
Written by
Founder & editor
Akram Afkir runs All About Crochet from Casablanca, Morocco, and is responsible for the patterns, tutorials and guides published on the site.