Crochet Hook Sizes Chart (mm, US & UK Conversions)

Crochet hook sizes chart (mm, US & UK)

Here's the full conversion chart. Bookmark it, or grab the printable version below, and you'll never second-guess a hook size again.

Now, a quick explainer on why there are three different labels in the first place.

How crochet hook sizes work (mm vs US vs UK)

Three different labels for the same hooks — no wonder it's confusing. Here's the simple logic behind each one.

• Millimeters (mm) — the actual diameter of the hook's shaft, and the one number that's the same worldwide. Bigger mm = bigger hook. This is the label to trust.
• US sizes (letters + numbers) — the US labels hooks with a letter and a paired number, like G/6, H/8, I/9. As the letters climb the alphabet, the hook gets bigger.
• UK sizes (numbers) — the UK uses a number system that runs backwards: the bigger the number, the smaller the hook. So a UK 13 is tiny and a UK 000 is huge. This reverse scale trips up almost everyone.

The other thing that changes which hook to grab isn't the label at all — it's your yarn. Let's line those up.

Which hook size for which yarn weight

The hook you reach for depends mostly on your yarn's thickness (its weight). Thicker yarn needs a bigger hook, thinner yarn a smaller one. Here's the go-to pairing:

When to go up or down a size

The recommended hook is a starting point, not a rule. If your fabric comes out stiff and dense, go up a hook size. If it's loose and holey, go down. Your yarn stays the same — you just change the hook until the fabric feels right.

Learn more about pairing tools and fiber in our full crochet tools & yarn guide.

Steel hooks (for thread crochet)

If you've ever seen a tiny hook next to a spool of fine thread, that's a steel hook, used for delicate thread crochet like doilies, lace, and fine edgings. They have their own sizing system, and it catches everyone out, so it's worth a separate chart.

The important twist: steel hook numbers run backwards. The higher the number, the smaller the hook — the opposite of regular yarn hooks. So a steel size 14 is teeny, and a size 00 is the biggest of the bunch.

Most beginners won't touch steel hooks for a while, so if that's you, feel free to skip this and come back when you're ready to try thread crochet.

How to find the size of an unmarked hook

Inherited a hook with no size on it? Or the label's rubbed off? It happens all the time, and there are two easy ways to figure out what you've got.

1. Use a hook/needle gauge. This is the reliable one. A hook gauge is a small flat tool with holes of different sizes labeled in mm. Slide the shaft of your hook (not the pointed head) through the holes — the smallest hole it fits through snugly is your size. Cheap, quick, and exact.

2. Measure it with a ruler. No gauge handy? Lay the hook on a millimeter ruler and measure the diameter of the shaft(the straight part behind the hook head, not the thick handle). Match that measurement to the mm column in the chart above. It's less precise than a gauge, but it'll get you close.

What size hook should a beginner use?

Why 5.0mm wins for learning:

• Easy to hold and control — not too big, not too fiddly.
• Pairs with worsted yarn, the smooth, mid-thick yarn most beginner patterns use.
• Shows your stitches clearly, so you can see exactly what your hook is doing.
• Works with tons of free patterns, so you'll never be short of things to make.

Once you're comfortable, you'll naturally collect other sizes as your patterns call for them, but a single 5.0mm and a ball of worsted yarn is genuinely all you need to start. Ready to put it to use? Learn the basics in our crochet stitches guide, then browse our →free beginner patterns.