Crochet Hook Sizes: Chart & Converter
Millimeters to US, UK, and Japanese hook sizes — an interactive converter plus the full chart, with typical yarn pairings.
Metric
5 mm
US
H/8
UK & Canada
6
Japan
8/0
Typical use: Worsted (the classic)
Full crochet hook size chart
| mm | US | UK & Canada | Japan | Typical yarn |
|---|---|---|---|---|
| 2 | A/0 | 14 | 2/0 | Lace / thread |
| 2.25 | B/1 | 13 | — | Lace / thread |
| 2.5 | C/2 | 12 | 4/0 | Fingering |
| 2.75 | C/2 | 11 | — | Fingering |
| 3 | — | 10 | 5/0 | Fingering / sport |
| 3.25 | D/3 | 10 | — | Sport |
| 3.5 | E/4 | 9 | 6/0 | Sport / DK |
| 3.75 | F/5 | 8 | — | DK |
| 4 | G/6 | 8 | 7/0 | DK |
| 4.5 | 7 | 7 | 7.5/0 | DK / worsted |
| 5 | H/8 | 6 | 8/0 | Worsted (the classic) |
| 5.5 | I/9 | 5 | 9/0 | Worsted |
| 6 | J/10 | 4 | 10/0 | Worsted / aran |
| 6.5 | K/10.5 | 3 | 10.5/0 | Aran / bulky |
| 7 | — | 2 | — | Bulky |
| 8 | L/11 | 1 | — | Bulky |
| 9 | M/N/13 | 00 | — | Super bulky |
| 10 | N/P/15 | 000 | — | Super bulky |
| 12 | O/17 | — | — | Jumbo |
| 15 | P/Q | — | — | Jumbo |
| 19 | S/35 | — | — | Jumbo |
| 25 | T/U/X | — | — | Jumbo |
UK/Japan equivalents are the closest standard sizes — a few metric sizes have no exact match. When in doubt, swatch.
Crochet hooks are labeled in four different systems: millimeters (metric), US letters and numbers, UK/Canada numbers (which run backwards — bigger number, smaller hook), and Japanese numbers. Patterns rarely tell you which system they mean, and hook brands mix them on the same packaging.
The converter above translates any size instantly, and the full chart covers 2.0 mm to 25 mm with typical yarn pairings. When a pattern says "G hook" and your hook only shows millimeters, this is the page to bookmark.
What you get
Instant 4-way conversion
Pick millimeters or a US letter and see US, UK/Canada, and Japan equivalents together.
Full 2.0–25 mm chart
Every standard size from steel-thread territory to jumbo blanket hooks, in one printable table.
Typical yarn pairings
Each size shows the yarn weight it's most often used with, from lace thread to jumbo roving.
Highlighted match
The size you converted stays highlighted in the chart so you can see its neighbors at a glance.
Honest equivalents
Where a metric size has no exact UK or Japan match, the chart says so — no false precision.
Free, no sign-up
Works offline in your browser. Bookmark it and forget the conversion anxiety.
How to convert crochet hook sizes
Check what's printed on your hook
Most modern hooks show millimeters, sometimes alongside a US letter. Older or vintage hooks may show only a number — that's often the UK system.
Convert with the tool above
Choose the size you have — in mm or US letters — and read off the US, UK, and Japanese equivalents.
Match the pattern's gauge, not just the size
Sizes vary slightly between brands and systems. Always swatch: if your gauge is off, go up or down a size even when the conversion is exact.
Converter vs. memorizing the chart
| Interactive converter | Memory and guesswork | |
|---|---|---|
| Speed | Two clicks to all four systems | Scroll a wall of numbers every time |
| UK numbers | Handled — including the backwards direction | The classic way to grab the wrong hook |
| Ambiguous sizes | Flags sizes with no exact equivalent | Close enough… until the gauge swatch says otherwise |
| Learning | Chart with yarn pairings teaches as you convert | You convert and learn nothing |
Frequently asked questions
What size is an H crochet hook?
An H hook (H/8 in the US system) is 5.0 mm. It's the classic size for worsted-weight (#4) yarn and the most commonly used hook in US patterns — if a pattern just says "H", it means 5.0 mm.
What size is a G hook, and what about other letters?
G/6 = 4.0 mm, I/9 = 5.5 mm, J/10 = 6.0 mm, K/10.5 = 6.5 mm, F/5 = 3.75 mm, E/4 = 3.5 mm, B/1 = 2.25 mm, C/2 = 2.75 mm, D/3 = 3.25 mm. Use the converter above for the full list with UK and Japan equivalents.
Why do UK crochet hook numbers go backwards?
UK and Canada sizes are numbered in reverse: the bigger the number, the smaller the hook. A UK 14 is 2.0 mm while a UK 000 is 10 mm. It's a legacy of old wire-gauge standards. When in doubt, always trust millimeters — they're the only system that's unambiguous.
What size crochet hook should a beginner use?
Start with a 5.0 mm (H/8) or 5.5 mm (I/9) hook and smooth, light-colored worsted-weight yarn. Mid-range hooks make stitches easy to see and control; very small and very large hooks both fight beginners.
Do crochet hook sizes vary between brands?
Slightly, yes — especially between US letter hooks from different makers and in very old hooks. Two "G" hooks can differ by a quarter millimeter. That's why patterns give a gauge: match the gauge with whatever hook gets you there, regardless of its label.
Is this crochet hook conversion chart free?
Yes — free with no sign-up, and it runs in your browser so it works even without a connection once loaded.