Free Crochet Craft Tools & Calculators
Interactive calculators, row counters, size converters, and planning tools engineered specifically for yarn crafters. 100% offline-ready.
Hook Size Converter
Crochet Hook Size Converter
Convert metric (mm) hook sizes to US letter names, UK numbers, and Japanese sizes.
| Metric (mm) | US Letter | UK Number | Japan Size | Recommended Yarn Weight |
|---|---|---|---|---|
| 2.00 mm | - | 14 | 2/0 | Lace / Thread (#0) |
| 2.25 mm | B-1 | 13 | 3/0 | Super Fine / Sock (#1) |
| 2.75 mm | C-2 | 12 | 4/0 | Super Fine / Fingering (#1) |
| 3.25 mm | D-3 | 10 | 5/0 | Fine / Sport (#2) |
| 3.50 mm | E-4 | 9 | 6/0 | Fine / Sport (#2) / Amigurumi |
| 3.75 mm | F-5 | 8 | - | Light / DK (#3) |
| 4.00 mm | G-6 | 8 | 7/0 | Light / DK (#3) |
| 4.50 mm | 7 | 7 | 7.5/0 | Worsted / Aran (#4) |
| 5.00 mm | H-8 | 6 | 8/0 | Worsted / Afghan (#4) |
| 5.50 mm | I-9 | 5 | 9/0 | Worsted / Heavy Aran (#4) |
| 6.00 mm | J-10 | 4 | 10/0 | Bulky (#5) |
| 6.50 mm | K-10.5 | 3 | - | Bulky (#5) |
| 8.00 mm | L-11 | 0 | - | Super Bulky (#6) |
| 9.00 mm | M/N-13 | 00 | - | Super Bulky (#6) |
| 10.00 mm | N/P-15 | 000 | - | Jumbo (#7) |
Crochet Hook Size Conversion Chart — Metric mm, US Letter & UK Sizes
Navigate vintage patterns and international charts with precise millimeter to letter and steel number conversions.
Crochet Hook Size Conversion Chart - Metric mm, US Letters & UK Numbers
Navigating vintage crochet patterns, international PDF downloads, or Japanese amigurumi charts requires accurate crochet hook conversions. Use our free crochet hook size converter to map metric millimeter (mm) dimensions to US letter names, UK steel numbers, and Japanese hook sizes instantly.
Comprehensive International Hook Size Conversion Matrix
| Metric Size (mm) | US Letter / Name | UK / Canadian Size | Japanese Hook Size | Best For Yarn Weight |
|---|---|---|---|---|
| 2.00 mm | — | 14 | 2/0 | #0 Lace / Thread |
| 2.25 mm | B - 1 | 13 | — | #1 Sock / Fingering |
| 2.50 mm | — | 12 | 4/0 | #1 Sock / Fingering |
| 2.75 mm | C - 2 | — | — | #1 Super Fine |
| 3.00 mm | — | 11 | 5/0 | #2 Sport |
| 3.25 mm | D - 3 | 10 | — | #2 Sport |
| 3.50 mm | E - 4 | 9 | 6/0 | #2 Sport / #3 DK |
| 3.75 mm | F - 5 | — | — | #3 Light / DK |
| 4.00 mm | G - 6 | 8 | 7/0 | #3 Light / DK |
| 4.50 mm | 7 | 7 | 7.5/0 | #3 DK / #4 Worsted |
| 5.00 mm | H - 8 | 6 | 8/0 | #4 Medium / Worsted |
| 5.50 mm | I - 9 | 5 | 9/0 | #4 Medium / Worsted |
| 6.00 mm | J - 10 | 4 | 10/0 | #4 Worsted / #5 Bulky |
| 6.50 mm | K - 10.5 | 3 | — | #5 Bulky / Chunky |
| 8.00 mm | L - 11 | 0 | — | #5 Bulky / #6 Super Bulky |
| 9.00 mm | M / N - 13 | 00 | — | #6 Super Bulky |
| 10.00 mm | N / P - 15 | 000 | — | #6 Super Bulky |
| 15.00 mm | P / Q | — | — | #7 Jumbo |
Frequently Asked Questions
Q: What US size is a 5.0 mm crochet hook?
A: A 5.0 mm hook is a US H-8 (or UK size 6). It is the most popular hook size in the world for #4 worsted weight yarn.
Q: Why do hook letter names vary between manufacturers?
A: Some brands label 3.75mm as "F" while others label 4.0mm as "G". Always rely on the exact millimeter (mm) measurement stamped on the hook shaft for precise gauge matching.