Crochet Hook Sizes Chart: mm, US Letters & Yarn Weights
By the PLoMUS Editorial Team · Last updated October 27, 2026 · Data: Craft Yarn Council standards
Quick answer: Go by the millimeter (mm) size. Letters and numbers like "H-8" are names, and the Craft Yarn Council says those names vary from company to company. The millimeter size is the measurement you can trust. The sizes people look up most often, per the Craft Yarn Council chart:
- 3.5 mm = E-4
- 4 mm = G-6
- 5 mm = H-8
- 5.5 mm = I-9
- 6 mm = J-10
- Worsted (weight 4) yarn: 5.5 to 6.5 mm (I-9 to K-10½) is the suggested hook range
Hook labels can be confusing. One package says "H-8," another says "5 mm," and an older hook might show only a letter. This page puts the official US size names next to their millimeter sizes, then shows which hook range goes with each yarn weight. Both tables are built from the Craft Yarn Council, the yarn industry trade group that publishes the standards its member companies set.
Crochet hook sizes chart (mm to US)
The table below lists every regular (non-steel) crochet hook size in the Craft Yarn Council chart. We split each US name into its letter part and its number part so you can match a hook no matter which half is printed on it.
| Size (mm) | US name | Letter part | Number part |
|---|---|---|---|
| Small hooks (2.25 to 3.75 mm) | |||
| 2.25 | B-1 | B | 1 |
| 2.5 | none listed | none | none |
| 2.75 | C-2 | C | 2 |
| 3.125 | D | D | none |
| 3.25 | D-3 | D | 3 |
| 3.5 | E-4 | E | 4 |
| 3.75 | F-5 | F | 5 |
| Medium hooks (4 to 6.5 mm) | |||
| 4 | G-6 | G | 6 |
| 4.25 | G | G | none |
| 4.5 | 7 | none | 7 |
| 5 | H-8 | H | 8 |
| 5.25 | I | I | none |
| 5.5 | I-9 | I | 9 |
| 5.75 | J | J | none |
| 6 | J-10 | J | 10 |
| 6.5 | K-10½ | K | 10½ |
| Large hooks (7 to 12 mm) | |||
| 7 | none listed | none | none |
| 8 | L-11 | L | 11 |
| 9 | M/N-13 | M or N | 13 |
| 10 | N/P-15 | N or P | 15 |
| 11.5 | P-16 | P | 16 |
| 12 | none listed | none | none |
| Jumbo hooks (15 mm and up) | |||
| 15 | P/Q | P or Q | none |
| 15.75 | Q | Q | none |
| 16 | Q | Q | none |
| 19 | S | S | none |
| 25 | T/U/X | T, U or X | none |
| 30 | T/X | T or X | none |
Source: Craft Yarn Council, Hooks & Needles, all 28 rows checked October 27, 2026 (as of October 2026). "None listed" means the Craft Yarn Council gives no US letter or number for that size. The size-group headings are ours.
What about UK and Canadian hook sizes?
Older UK and Canadian hooks may be stamped with a different number system. The Craft Yarn Council chart does not list those numbers, and we could not confirm a conversion against a primary source, so we are not printing one. The practical rule is the same either way: if a hook shows a millimeter size, go by that.
Yarn weight to hook size chart
The Craft Yarn Council sorts yarn into eight weight categories, numbered 0 to 7. You will usually find the number inside a small yarn-skein symbol on the label. Here is the hook range it suggests for each category, along with the typical crochet gauge (single crochet stitches in 4 inches).
| Weight number and name | Yarn names you will see on labels | Suggested hook (mm) | Suggested hook (US) | Typical gauge, sc per 4 in |
|---|---|---|---|---|
| 0 Lace | Fingering, 10-count crochet thread | Steel 1.6 to 1.4; regular 2.25 | Steel 6, 7, 8; regular B-1 | 32 to 42 double crochet* |
| 1 Super Fine | Sock, fingering, baby | 2.25 to 3.5 | B-1 to E-4 | 21 to 32 |
| 2 Fine | Sport, baby | 3.5 to 4.5 | E-4 to 7 | 16 to 20 |
| 3 Light | DK, light worsted | 4.5 to 5.5 | 7 to I-9 | 12 to 17 |
| 4 Medium | Worsted, afghan, aran | 5.5 to 6.5 | I-9 to K-10½ | 11 to 14 |
| 5 Bulky | Chunky, craft, rug | 6.5 to 9 | K-10½ to M-13 | 8 to 11 |
| 6 Super Bulky | Super bulky, roving | 9 to 15 | M-13 to Q | 7 to 9 |
| 7 Jumbo | Jumbo, roving | 15 and larger | Q and larger | 6 or fewer |
Source: Craft Yarn Council, Standard Yarn Weight System, checked October 27, 2026 (as of October 2026). *The Lace row gauge is given in double crochet. The Craft Yarn Council labels all of these ranges "guidelines only": they reflect the most commonly used hook sizes, not rules.
One note on Lace weight: the Craft Yarn Council points out that lace yarns are usually worked on larger hooks than you might expect, to make open, lacy fabric. That is why a gauge range is hard to pin down for weight 0. With lace, follow the gauge in your pattern.
How to read these charts
- Start with millimeters. The Craft Yarn Council calls the mm size an accurate measurement. The letter is a label. If two brands disagree on the letter, trust the mm.
- A letter plus a number is one hook. "H-8" is not two sizes. H is the letter name and 8 is the number name for the same 5 mm hook.
- Some sizes have only a letter or only a number. In the chart, 4.25 mm is just "G" and 4.5 mm is just "7."
- Fractions are part of the name. K-10½ is a 6.5 mm hook, not a 10 mm or 10.5 mm hook.
- Slashes mean more than one name is in use. A 9 mm hook may be sold as M or N, which is why the chart shows M/N-13.
- The same letter can show up more than once. "Q" appears at both 15.75 mm and 16 mm, and "G" at both 4 mm and 4.25 mm. Another reason to check the mm.
- Yarn ranges share their edges. 5.5 mm sits at the top of Light (3) and the bottom of Medium (4). Your pattern's gauge decides which end you use.
- Steel hooks run backward. Steel hooks, used with crochet thread and very fine yarn, are numbered so that a higher number means a smaller hook. The Craft Yarn Council notes this is the reverse of regular hook sizing.
Which hook size should I use?
Use this order of priority. It settles almost every "which hook?" question:
- Your pattern's gauge comes first. If the pattern says "5 mm hook, 14 sc = 4 in," the gauge is the goal and the hook is the designer's suggestion for reaching it.
- The yarn label comes second. No pattern? Look for the weight number and suggested hook on the yarn label.
- The chart above comes third. No label either? Use the Craft Yarn Council range for the yarn's weight and start in the middle.
| What you have | Where to start | Then |
|---|---|---|
| Pattern with gauge | The hook the pattern names | Make a swatch; change hook size until gauge matches |
| Yarn label, no pattern | The hook printed on the label | Adjust for the fabric you want (tighter or looser) |
| Only the weight number | The middle of the Craft Yarn Council range above | Swatch and adjust |
| An unlabeled hook | Check the handle for a mm stamp | If there is none, a hook gauge tool can tell you the size |
Swatch advice from the Craft Yarn Council crochet gauge guide (PDF), checked October 27, 2026.
How to adjust: the Craft Yarn Council's gauge guide says that if your swatch has more stitches per inch than the pattern, use the next larger hook. If it has fewer, use the next smaller hook. Keep going until the swatch matches.
Reading a pattern written in UK terms? Stitch names change too, and that changes the size of your fabric. See our US vs UK Crochet Terms Conversion Chart before you start.
Common mistakes
- Buying by letter alone. Letters and numbers vary by brand. Check the mm on the package before you buy.
- Treating the yarn chart as a rule. The ranges are a starting point. A pattern's gauge always wins.
- Skipping the gauge swatch. It takes a few minutes and catches a wrong hook before you have worked a whole project.
- Reading "10½" as millimeters. K-10½ is 6.5 mm. US numbers are names, not measurements.
- Mixing up steel and regular hooks. A steel hook numbered 7 and a regular hook numbered 7 are very different sizes, because steel numbering runs in reverse.
FAQ
Is an H-8 hook the same as a 5 mm hook?
In the Craft Yarn Council chart, yes: H-8 is listed as 5 mm. Because brands can label sizes differently, the Craft Yarn Council advises relying on the millimeter size printed on the package. If the package says 5 mm, you have the right hook, whatever letter it shows.
What size hook should I use with worsted (weight 4) yarn?
The Craft Yarn Council's suggested range for Medium (4) yarn, which includes worsted, afghan and aran, is 5.5 to 6.5 mm (I-9 to K-10½). If you have a pattern, use its hook and gauge instead, since the designer may want a tighter or looser fabric.
What hook goes with chunky (weight 5) yarn?
The suggested range for Bulky (5) yarn, which includes chunky, craft and rug yarns, is 6.5 to 9 mm (K-10½ to M-13). Start in the middle of that range, make a swatch, and go up or down a size depending on how stiff or drapey you want the fabric.
My project is coming out bigger than the pattern. What should I change?
Bigger fabric usually means you have fewer stitches per inch than the pattern's gauge. The Craft Yarn Council's gauge guide says to switch to a smaller hook in that case, and to a larger hook if you have more stitches per inch. Also check that you are reading the stitch names in the right terms (US or UK).
Why do steel hook numbers seem backward?
Steel hooks follow their own numbering, where a higher number means a smaller hook. That is the opposite of regular hooks. The Craft Yarn Council also notes that steel hook numbering varies between sources, so with thread work, always make a gauge swatch and compare it to your pattern rather than trusting the number alone.
Can I use a 5.5 mm hook for both DK and worsted yarn?
Yes, it is a reasonable place to start for either. 5.5 mm (I-9) is the top of the Light (3) range, which includes DK, and the bottom of the Medium (4) range, which includes worsted. Make a swatch and compare it to your pattern's gauge to decide whether to stay there.
Related guide
Crochet Pumpkin Size Calculator: stitches and rows for any size
Sources
- Craft Yarn Council: Hooks & Needles (hook sizes, brand variation note), checked October 27, 2026
- Craft Yarn Council: Standard Yarn Weight System (weight categories, hook ranges, gauge, lace note), checked October 27, 2026
- Craft Yarn Council: Steel Crochet Hook and Crochet Thread Sizes (steel numbering), checked October 27, 2026
- Craft Yarn Council: crochet gauge guide (PDF) (larger or smaller hook advice), checked October 27, 2026
How this article was made
Written by the PLoMUS Editorial Team with AI drafting assistance; facts checked against the sources above on October 27, 2026. The tables were built by our team from the Craft Yarn Council's published standards; the layout, size groupings and decision table are our own. We did not measure or test hooks for this article. We will recheck these standards once a year.
Update log: October 27, 2026: corrections after editorial review.
October 28, 2026: Added a summary image.
October 28, 2026: Added a link to a related guide on this blog.
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