Crochet hook size chart
Crochet hooks are measured in millimetres, and the US letter is just a nickname for that measurement. A 5.0mm hook is a US H-8, a 6.0mm is a J-10, and a 4.0mm is a G-6. Older UK and Canadian patterns use a separate number scale that runs backwards, so a 4.0mm hook is a UK 8. The chart below converts all three, and shows which yarn weight each hook is usually paired with.
Crochet hook conversion chart
Sizes between 3.5mm and 6.5mm cover most beginner patterns. If a pattern gives only a letter, work from the millimetre column, since letters drift a little between brands.
| Millimetres | US size | Old UK/Canada | Usual yarn weight |
|---|---|---|---|
| 2.25 mm | B-1 | 13 | 1 Super Fine |
| 2.75 mm | C-2 | 12 | 1 Super Fine |
| 3.25 mm | D-3 | 10 | 1 Super Fine, 2 Fine |
| 3.5 mm | E-4 | 9 | 2 Fine |
| 3.75 mm | F-5 | - | 2 Fine |
| 4.0 mm | G-6 | 8 | 3 Light |
| 4.5 mm | 7 | 7 | 3 Light |
| 5.0 mm | H-8 | 6 | 3 Light, 4 Medium |
| 5.5 mm | I-9 | 5 | 4 Medium |
| 6.0 mm | J-10 | 4 | 4 Medium |
| 6.5 mm | K-10.5 | 3 | 4 Medium, 5 Bulky |
| 8.0 mm | L-11 | 0 | 5 Bulky |
| 9.0 mm | M/N-13 | 00 | 5 Bulky, 6 Super Bulky |
| 10.0 mm | N/P-15 | 000 | 6 Super Bulky |
| 15.0 mm | P/Q | - | 6 Super Bulky, 7 Jumbo |
| 16.0 mm | Q | - | 7 Jumbo |
| 19.0 mm | S | - | 7 Jumbo |
Not sure which weight your yarn is? Check the yarn weight chart.
Steel hooks for crochet thread
Steel hooks are numbered on their own scale, and it runs backwards: a higher number is a smaller hook. They are used for thread crochet, doilies, and fine lace rather than yarn.
| Millimetres | US size |
|---|---|
| 0.75 mm | 14 |
| 0.9 mm | 12 |
| 1.05 mm | 11 |
| 1.25 mm | 8 |
| 1.5 mm | 6 |
| 1.65 mm | 4 |
| 1.9 mm | 0 |
Knitting needle size conversion
Needles use the same millimetre measurement, with a different US number scale. If you crochet and knit, this is the other half of the same chart.
| Millimetres | US size | Old UK/Canada |
|---|---|---|
| 2.0 mm | 0 | 14 |
| 2.25 mm | 1 | 13 |
| 2.75 mm | 2 | 12 |
| 3.0 mm | - | 11 |
| 3.25 mm | 3 | 10 |
| 3.5 mm | 4 | - |
| 3.75 mm | 5 | 9 |
| 4.0 mm | 6 | 8 |
| 4.5 mm | 7 | 7 |
| 5.0 mm | 8 | 6 |
| 5.5 mm | 9 | 5 |
| 6.0 mm | 10 | 4 |
| 6.5 mm | 10.5 | 3 |
| 8.0 mm | 11 | 0 |
| 9.0 mm | 13 | 00 |
| 10.0 mm | 15 | 000 |
| 12.75 mm | 17 | - |
| 15.0 mm | 19 | - |
| 19.0 mm | 35 | - |
| 25.0 mm | 50 | - |
Common questions
What hook size should I use for worsted weight yarn?
A 5.0mm (H-8) to 6.5mm (K-10.5) hook is the usual range for worsted weight yarn, which is weight 4 on the standard scale. Most worsted patterns assume a 5.0mm or 5.5mm hook.
Start with the size printed on the yarn label, then swatch. If your fabric comes out stiff and small, go up a size. If it comes out loose and floppy, go down. Amigurumi is the deliberate exception: it uses a hook one or two sizes smaller than the label suggests so the stitches stay tight enough to hide the stuffing.
What do the US hook letters and numbers mean?
US hooks carry a letter and a number together, like H-8 or K-10.5. The pair is a label, not a measurement, and it maps onto exactly one millimetre size.
Two sizes break the pattern. The 4.5mm hook is a plain 7 with no letter, and the 3.75mm F-5 has no old UK equivalent at all. Above 10mm, brands stop agreeing entirely, which is why very large hooks are usually sold by millimetre.
Are UK and US crochet hook sizes different?
Modern UK patterns use millimetres, so a UK 4.0mm hook and a US G-6 are the same hook. The confusion comes from older UK and Canadian patterns, which use a number scale that runs the opposite way to the US one: as the number goes down, the hook gets bigger.
Hook sizing is a separate problem from stitch naming. UK patterns also use different names for the stitches themselves, where a UK double crochet is the short stitch a US pattern calls a single crochet. Check both before you start.
Does hook size change my gauge?
Yes, and it is the main lever you have. A bigger hook makes bigger stitches, so fewer of them fit in four inches and the finished piece comes out larger. A smaller hook does the reverse.
That is why patterns give a gauge rather than trusting the hook size alone. Two people can work the same pattern with the same 5.0mm hook and end up with different sizes, because tension is personal. Swatch, measure, and change hook size until your gauge matches the pattern.
Once you have picked a hook, measure your gauge and run the numbers through the free gauge calculator.