Crochet Hook Size Chart

Crochet hook sizes: US, metric and UK

A crochet hook's size is the diameter of its shank, the smooth part where the loops sit, measured in millimeters. US hooks also carry a letter, a number or both. The chart gives the Craft Yarn Council's standard US label for each size, the old UK number where published charts agree, and the yarn weights whose recommended hook range includes it.

Look up any hook with the tool above: type a letter, a number or a label such as K-10½, or switch to millimeters to find the nearest standard size.

What the chart can't settle on its own:

• Letters vary between brands; millimeters don't. The slashed labels (M/N-13, N/P-15, P/Q, T/U/X) exist because brands put different letters on the same size. A hook marked N may be 9 mm or 10 mm, so read the number or the millimeters.
• G-6 and Q have brand variants. Some brands, Boye among them, make their G-6 4.25 mm instead of 4 mm, and some sell their Q hook as 16 mm.
• 7 mm and 12 mm have no US label. They are sold by millimeters. The 4.5 mm hook has a number, 7, but no letter.
• Old UK sizes are only listed where charts agree. From 4 mm to 10 mm the conversions are consistent. Below 4 mm published charts disagree, especially around 3.5 and 3.75 mm, so the chart says "Varies" rather than guessing. Hooks over 10 mm never had an old UK number.
• Two yarn weights means the edge of both ranges. The Craft Yarn Council's hook ranges meet at sizes like 5.5 mm, the top of the 3 Light range and the bottom of 4 Medium.

Hook sizes by yarn weight

The Craft Yarn Council's yarn weight system gives a hook range for each weight, and most yarn labels print it. The gauges are single crochet over 4 inches, except lace weight, which is given in double crochet. These are the same ranges as the chart on the knitting and crochet page.

Use these ranges to choose a hook to swatch with. The gauge in your pattern decides the hook you finish with.

How to read the size on a crochet hook

Most hooks print the size on the flat thumb rest or on the handle, usually as a letter and number plus millimeters, such as "H-8 5 mm" or "H/8 – 5.00 mm". The millimeters are the measurement; the letter and number are a label. Hooks from outside the US may print only millimeters, or a different numbering system beside them, so the millimeters are the part to compare.

The millimeter size is the diameter of the shank, the straight section between the throat (the groove under the head) and the thumb rest. That is where your loops sit, so it sets the size of your stitches. The shape of the head doesn't change the size.

If the marking has worn off a hook, push the shank through the holes of a knitting needle gauge. Most gauges are marked in millimeters, and the smallest hole the shank slides through is its size.

How hook size changes your gauge

A larger hook makes larger loops, so you get fewer stitches and rows per 4 inches and a looser, softer fabric. A smaller hook gives more stitches per 4 inches and a firmer fabric. That gives a simple rule when your swatch doesn't match the pattern:

• Too many stitches per 4 inches: your stitches are too small. Go up a hook size.
• Too few stitches per 4 inches: your stitches are too big. Go down a hook size.

Change one size at a time and make a new swatch, because the step from one hook to the next is not the same size everywhere on the chart.

Small differences add up. A baby blanket 126 single crochet wide measures 36 inches at 14 stitches per 4 inches. If a different hook changes your gauge to 13 stitches per 4 inches, the same 126 stitches measure 38.8 inches; at 15 stitches, they measure 33.6 inches. A single stitch of gauge moves the width by more than 2 inches. Once you have a gauge you like, the crochet blanket size calculator works out the chain and rows for it, and the yarn calculator uses the new swatch to estimate how much yarn to buy.

Steel hooks for crochet thread

Hooks finer than B-1 (2.25 mm) are usually steel hooks, made for crochet thread and fine lace. They have their own numbers, and those run backward: the higher the number, the smaller the hook, so a size 10 steel hook is far finer than a J-10. Brands don't agree on the millimeters for each steel number, so this chart doesn't list them. Buy and substitute steel hooks by the millimeter size printed on the hook. For lace-weight yarn, the Craft Yarn Council suggests steel hooks 6 to 8 or a regular B-1.

Tips for choosing a hook

• Start with the yarn label. Most ball bands print a recommended hook size. Use it for your first swatch.
• Match the gauge, not the letter. The hook in a pattern is the one the designer used. If your gauge is different, change hooks until it matches.
• Chain loosely. If your foundation chain comes out tighter than the rows above it, make the chain with a hook one or two sizes larger.
• Go smaller for amigurumi. Stuffed toys are usually worked on a smaller hook than the yarn label suggests, so the fabric is tight and the stuffing doesn't show.
• Go bigger for drape. Shawls and lacy stitches open up and hang better on a hook larger than the label suggests.
• Keep one brand within a project. Inline heads, as on Susan Bates hooks, and tapered heads, as on Boye hooks, form loops differently, so two hooks of the same millimeter size can give slightly different gauges.
• Shop by millimeters. Sizes such as 7 mm and 12 mm have no US label, and others carry different letters from brand to brand.