Start with the millimetre marking whenever it is available. Letter and number labels are convenient pattern references, but manufacturers do not use them with perfect consistency.
Enter the physical diameter. Exact common matches appear in the result; the complete reference remains below.
10 mm
| Millimetres | US label |
|---|---|
| 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-10½ |
| 8 mm | L-11 |
| 9 mm | M/N-13 |
| 10 mm | N/P-15 |
A hook marked 5 mm is commonly labelled H-8 in US ranges.
Why millimetres come first
A millimetre value describes the physical diameter of the hook shaft. A US letter or number is a naming convention, and manufacturers do not apply every label identically. StitchMeasure therefore keeps the metric diameter visible and returns the regional label as a pattern-reading aid rather than an absolute standard.
If a pattern says H-8 and your hook says 5 mm, those markings commonly describe the same nominal size. Confirm the tool, then make a swatch: matching a hook label is only the start of matching the fabric.
Resolve a mismatch
Read every marking on the pattern and hook. If they disagree, anchor the comparison to the physical millimetre size and use the pattern gauge to test the choice. Never identify an unmarked hook from its colour or handle style.
How to use this page
- Choose the millimetre size printed on the hook or pattern.
- Read the closest commonly used US label.
- Confirm the millimetre marking on the actual tool before starting your project.
What to check before you rely on the result
- Regional labels are approximate, not physical measurements.
- Older or brand-specific hooks may use a different label.
Source note
This original presentation was checked against the relevant Craft Yarn Council reference. Regional labels may vary; no third-party graphic or table layout is reproduced.
Consulted authority ↗