Crochet Hook Sizes: Chart and Converter
Look up a crochet hook by millimeters or its US label. Use the table to compare common sizes, identify labels with more than one diameter and choose a starting point for your next swatch. The metric size on your actual hook is more reliable than assuming every manufacturer uses the same letter.
Find a hook size
Metric and US crochet hook chart
| Diameter (mm) | US label |
|---|---|
| 2.25 | B-1 |
| 2.5 | Not assigned |
| 2.75 | C-2 |
| 3.125 | D |
| 3.25 | D-3 |
| 3.5 | E-4 |
| 3.75 | F-5 |
| 4 | G-6 |
| 4.25 | G |
| 4.5 | 7 |
| 5 | H-8 |
| 5.25 | I |
| 5.5 | I-9 |
| 5.75 | J |
| 6 | J-10 |
| 6.5 | K-10½ |
| 7 | Not assigned |
| 8 | L-11 |
| 9 | M/N-13 |
| 10 | N/P-15 |
| 11.5 | P-16 |
| 12 | Not assigned |
| 15 | P/Q |
| 15.75 | Q |
| 16 | Q |
| 19 | S |
| 25 | T/U/X |
| 30 | T/X |
Why one letter can have several sizes
A label such as G or Q can appear on more than one diameter. This finder shows every matching entry instead of silently selecting one. A missing label means that no US name is assigned in this reference, not that the diameter is unavailable.
Check gauge before changing hooks
Make a swatch in the intended stitch and compare its measurements with the pattern. If it is too large, try a smaller hook; if too small, try a larger one. Yarn, tension and stitch structure all affect the result.
Is H-8 the same as 5 mm?
Yes, H-8 corresponds to 5 mm in this reference. Confirm the metric marking on your hook.
Does this chart include steel thread hooks?
No. Steel thread hooks use a separate numbering system. Do not convert a steel hook number using this regular-hook table.
Can I enter a UK or Japanese size?
This version supports metric and US regular-hook sizes only. Check your manufacturer’s chart for other systems.
Sizing source: Craft Yarn Council: Hooks & Needles. Checked October 4, 2026.