Clover
clover-mfg.comJapanese notions, hooks, needles and Wonder Clips
KnittingCrochetSewing+2
Free tool · no sign-up · works offline once loaded
Crochet hook size chart & converter: mm, US letters, UK, steel
Convert crochet hook sizes between mm, US letters, old UK numbers and Japanese sizes, including steel thread hooks, and match hooks to yarn weight.
US letters vary a little between brands. Where two systems have no exact match, the converter shows the closest size and how far off it is.
Crochet hook size chart
| Metric | US | Old UK | Japanese | Notes |
|---|
Metric and US sizes follow the Craft Yarn Council standard. A dash means no standard size exists in that system.
Steel crochet hooks
| US steel size | Metric (by brand) |
|---|
Brands make the same steel number in slightly different diameters, so the Craft Yarn Council lists a range for most sizes.
Which hook for which yarn weight
| No. | Yarn weight | Gauge per 4 in | Hooks |
|---|
Three ways hooks are sized
Millimetres measure the shaft just below the throat of the hook, the part that sets the size of your loops. Every modern hook carries this number, and UK, European and Australian patterns use it on its own.
US letters run from B-1 (2.25 mm) to T/X (30 mm). The letter and number together, such as H-8, are the clearest way to read an American pattern. Watch for hooks marked with a letter only, which can be a quarter millimetre off.
Old UK numbers appear in vintage British patterns and run backwards, like old UK knitting needles: 14 is 2 mm and 000 is 10 mm.
Thread crochet
Doilies, edgings and fine lace use steel hooks and crochet thread. Thread is numbered the same way round as steel hooks: size 3 is thick, size 10 is the everyday weight and size 80 is very fine. Start with a steel 7 (1.5–1.65 mm) for size 10 thread, a 9 or 10 for size 20, and a 10 to 12 for size 30.
Reading an English pattern from another country? Check whether it uses US or UK stitch names with the US ↔ UK crochet terms converter.
How to use it
- Choose how your hook or pattern is labelled: metric, US letter, old UK, Japanese or US steel.
- Pick the size to see the same hook in every other system.
- Check which yarn weights the hook suits, or which crochet thread for a steel hook.
- Crochet a swatch and change hook size until your gauge matches the pattern.
Questions
What size is an H crochet hook in mm?
An H-8 hook is 5 mm. It is one of the most common hooks for worsted (medium, 4) yarn and matches the old UK size 6.
Why are some hook letters different between brands?
US letters were assigned by manufacturers before the sizes were standardised, so a plain G can be 4 or 4.25 mm and a J can be 5.75 or 6 mm. The number after the letter (G-6, J-10) points to the standard size. The millimetre size printed on the hook is always the reliable one.
How do steel crochet hook sizes work?
Steel hooks for thread crochet are numbered the opposite way to regular hooks: the bigger the number, the smaller the hook. They run from 00 (about 2.7–3.5 mm) down to 14 (about 0.75–0.9 mm). Size 10 crochet thread is usually worked with a steel 7 hook of about 1.5–1.65 mm.
What are Japanese crochet hook sizes?
Japanese hooks are written with a slash: 2/0 is 2 mm, 5/0 is 3 mm, 7/0 is 4 mm and 10/0 is 6 mm. Larger hooks are sold by millimetre. Fine Japanese lace hooks use a separate numbering system.
Which hook should I use for worsted yarn?
The Craft Yarn Council suggests 5.5–6.5 mm (I-9 to K-10½) hooks for medium weight yarn, although many crocheters start with 5 mm (H-8) for firmer fabric such as amigurumi.
Related sites and software
See allChiaoGoo
chiaogoo.comInterchangeable and circular knitting needles
Knitting
Dritz
dritz.comAmerican sewing notions and tools
SewingQuilting
OLFA
olfa.comRotary cutters and cutting mats
QuiltingSewing
AccuQuilt
accuquilt.comFabric die cutters for fast, accurate quilt pieces
Quilting
Bloc-Loc
blocloc.comRulers for trimming half-square triangles and flying geese
Quilting
More free tools
All 25 tools
Knitting Needle Size ConverterConvert knitting needle sizes between metric (mm), US, old UK and Japanese numbers, and see which needles suit each yarn weight.US ↔ UK Crochet Terms ConverterPaste a crochet pattern and translate it between US and UK terms in one click, with a full side-by-side chart and a searchable list of crochet abbreviations.WPI Yarn Weight CalculatorIdentify a mystery yarn from its wraps per inch, and convert yarn weight names between US, UK, Australian ply and the Craft Yarn Council 0–7 numbers.Blanket Size CalculatorCommon blanket sizes from lovey to king, a bed-fit calculator, and the stitches, rows or C2C tiles you need at your gauge.Hat Size CalculatorHead sizes from preemie to adult, then the stitches to cast on, hat height and crown shaping for your gauge, or the crown diameter for a crochet hat.Sock Size CalculatorEnter foot measurements or a shoe size and your gauge to get the cast-on, heel flap, gusset, foot length and toe for hand-knit socks.Photo to Pattern MakerTurn any photo into a cross-stitch chart, C2C crochet graph or knitting colourwork chart. Runs in your browser; your image never leaves your device.Cross-Stitch Fabric CalculatorWork out the finished design size and how much Aida, evenweave or linen to cut for any stitch count.