Crochet Hook Sizes Explained: A Complete Guide (with Size Chart)
If you've ever stared at a crochet hook wondering what “H-8” or “5.0 mm” actually means, you're not alone — crochet hook sizes are one of the most confusing things for new crocheters. The good news: once you understand how crochet hook sizes work, choosing the right crochet hook for any project becomes simple. This complete guide explains crochet hook sizes, includes a handy crochet hook size chart, covers US to metric (mm) conversions, and answers the big question for beginners: what size crochet hook should you start with?
How crochet hook sizes work
A crochet hook's size refers to the diameter of its shaft — the part that forms each stitch. The bigger the hook, the bigger the stitches, and the bigger (and looser) your finished crochet fabric. The smaller the hook, the tighter and finer the stitches.
Here's where it gets confusing: crochet hook sizes are labeled in two different systems at once.
- Metric (mm): The millimeter measurement is the true, universal crochet hook size — 4.0 mm, 5.0 mm, 5.5 mm, and so on. Because it's an actual measurement, the metric size never changes between brands, which is why experienced crocheters rely on it.
- US letter/number: In the United States, crochet hooks also carry a letter-and-number label like G-6, H-8, or J-10. This US crochet hook sizing is handy, but it isn't always perfectly consistent between manufacturers — so when in doubt, go by the mm.
You'll usually see both printed together on the hook, like “H-8 (5.0 mm).” When a crochet pattern calls for a specific hook, match the millimeter size first.
Jean says: When a crocheter asks me what hook they need, I always answer in millimeters. The mm is the real size — the letter is just a nickname.
Crochet hook size chart (US to mm)
Here's a crochet hook size chart showing the most common crochet hook sizes, with US letter/number labels and their metric (mm) conversions. These are the standard yarn-weight crochet hooks you'll use for the vast majority of projects.
| US size | Metric (mm) | Typical yarn weight |
|---|---|---|
| B-1 | 2.25 mm | Fingering / sock |
| C-2 | 2.75 mm | Fingering / sock |
| D-3 | 3.25 mm | Fingering / sport |
| E-4 | 3.5 mm | Sport |
| F-5 | 3.75 mm | Sport / DK |
| G-6 | 4.0 mm | DK |
| 7 | 4.5 mm | DK / worsted |
| H-8 | 5.0 mm | Worsted |
| I-9 | 5.5 mm | Worsted / aran |
| J-10 | 6.0 mm | Aran |
| K-10.5 | 6.5 mm | Aran / bulky |
| L-11 | 8.0 mm | Bulky |
| M/N-13 | 9.0 mm | Bulky / super bulky |
| N/P-15 | 10.0 mm | Super bulky |
| P/Q | 15.0 mm | Jumbo |
| Q | 16.0 mm | Jumbo |
| S | 19.0 mm | Jumbo |
Keep this crochet hook size chart handy — it's the quickest way to convert a US crochet hook size to mm (or mm to US) when you're following a pattern.
What size crochet hook should a beginner use?
If you're learning to crochet, the best crochet hook size for beginners is a mid-range H-8 (5.0 mm) or I-9 (5.5 mm) hook paired with a smooth worsted-weight yarn. This is the most recommended crochet hook size for beginners for a simple reason: a 5.0–5.5 mm hook is big enough to see and hold comfortably, small enough to feel natural, and it works perfectly with the easy-to-handle worsted yarn most beginner crochet patterns call for.
Start there, get comfortable with the basic stitches, and you can branch into other crochet hook sizes as your projects grow. (New to crochet entirely? Start with our guide to your first crochet project.)
Matching crochet hook size to yarn weight
Crochet hook sizes and yarn weight go hand in hand — thicker yarn needs a bigger crochet hook, and finer yarn needs a smaller one. Most yarn labels even print a recommended crochet hook size right on the band, so you don't have to guess. As a quick rule of thumb:
- Fingering / sock yarn: 2.25–3.5 mm crochet hooks (B-1 to E-4)
- Sport / DK yarn: 3.75–4.5 mm crochet hooks (F-5 to 7)
- Worsted / aran yarn: 5.0–6.5 mm crochet hooks (H-8 to K-10.5)
- Bulky / super bulky yarn: 8.0–10.0 mm crochet hooks (L-11 and up)
If you'd like to understand yarn weights in more depth, our yarn weights guide breaks down every weight from lace to jumbo.
Steel crochet hooks (for thread crochet)
There's one more category worth knowing: steel crochet hooks, used for fine thread crochet like doilies and lace. Steel crochet hook sizes use a separate numbering system where — confusingly — a higher number means a smaller hook (the opposite of regular hooks). Steel hooks run roughly from 0.75 mm to 1.75 mm. Unless you're crocheting with fine cotton thread, you won't need these, but it's good to know they exist so a “size 7 steel hook” doesn't throw you.
Crochet hook materials (a quick note)
Beyond crochet hook sizes, hooks also come in different materials — aluminum crochet hooks, bamboo, plastic, and ergonomic crochet hooks with soft, cushioned handles. Aluminum crochet hooks are smooth and fast; ergonomic crochet hooks are gentle on the hands during long crochet sessions and are a favorite for anyone with hand or wrist strain. Material is personal preference — the crochet hook size is what affects your stitches.
Does crochet hook size affect gauge?
Yes — crochet hook size is the main tool you use to hit the right gauge (the number of stitches and rows in a given measurement). If your crochet gauge swatch has too many stitches, size up your crochet hook; too few, size down. Always make a quick gauge swatch before starting a garment so your finished size comes out right.
The takeaway
Crochet hook sizes come down to three things: read the millimeter size first, match your crochet hook to your yarn weight, and start with an H-8 (5.0 mm) if you're a beginner. Keep the crochet hook size chart above bookmarked, and you'll never be confused at the yarn shop again.
Ready to find your next hook? Browse our crochet hooks — including smooth aluminum and comfortable ergonomic crochet hooks in every size — and our natural-fiber yarn collection, all hand-picked by a master knitter. Not sure which crochet hook size you need? Just ask; we're always happy to help. Free shipping on orders over $50.