Crochet guide
Crochet hook sizes explained
A crochet hook's size is the width of its shaft in millimeters. United States hooks carry a letter and a number as well, and those vary from maker to maker, so the millimeter size is the one to go by.
On this page 7 parts
What the size measures
The size of a crochet hook is the diameter of its shaft: the straight part just behind the hooked tip, where the loops sit while you work. A thicker shaft makes bigger loops, and bigger loops make bigger stitches.
Three ways a size is written
- Millimeters. The measurement itself, such as 5 mm.
- A United States letter and number. Regular hooks in the United States carry a letter, a number or both, such as H-8. The higher the number, the bigger the hook.
- An old United Kingdom number. United Kingdom patterns today usually give the hook in millimeters. Older patterns, and many conversion charts, use numbers that run the other way: the higher the number, the thinner the hook. A size 8 is 4 mm, and a size 4 is 6 mm.
Most hooks sold today are marked in millimeters and with a letter or number as well.
Why millimeters come first
The letters and numbers are not the same from one maker to the next. The G hook is the usual example: it is 4 mm from some makers and 4.25 mm from others. The millimeter size is a measurement, so it means the same on every hook.
When a pattern names a hook, go by the millimeters. When it gives only a letter, the chart below shows the usual size for it.
Hook size chart
| Millimeters | United States size |
|---|---|
| 2.25 mm | B-1 |
| 2.75 mm | C-2 |
| 3.25 mm | D-3 |
| 3.5 mm | E-4 |
| 3.75 mm | F-5 |
| 4 mm | G-6 |
| 4.5 mm | 7 |
| 5 mm | H-8 |
| 5.5 mm | I-9 |
| 6 mm | J-10 |
| 6.5 mm | K-10 1/2 |
| 8 mm | L-11 |
| 9 mm | M/N-13 |
| 10 mm | N/P-15 |
| 15 mm | P/Q |
| 16 mm | Q |
| 19 mm | S |
| 25 mm | T/U/X |
These are the sizes of the United States standard's table that other published charts give the same way. The standard lists more sizes in between, among them 4.25 mm (G) and 5.25 mm (I). On its yarn chart it writes two of the hooks above more shortly: M-13 for the 9 mm hook and Q for the 15 mm hook. The hook size chart has every row.
Steel hooks
The thinnest hooks are made of steel. They are used with crochet thread and lace-weight yarn.
Steel hooks have numbers of their own, and those run the other way from regular hooks: the higher the number, the smaller the hook.
Which size to use
- Following a pattern? Begin with the hook the pattern names.
- No pattern? The yarn's label suggests a hook size for that yarn.
- As a rule, thicker yarn takes a bigger hook and thinner yarn a smaller one.
Then let your gauge decide. If your swatch comes out larger than the pattern's gauge, make another with a smaller hook. If it comes out smaller, use a larger hook. Crochet gauge and how to measure it explains how.
To learn with, a medium-sized hook of 4 mm (G-6) to 5 mm (H-8) is a common choice.
A hook with no size on it
A hook gauge, also called a needle gauge, is a card with a series of holes, each marked with a size. Slide the shaft of the hook into the holes until you find the one it fits. That hole's size is the hook's size.
The hook size by yarn weight chart shows the usual range of hooks for each thickness of yarn, and yarn weights for crochet explains the thicknesses.