Crochet hook sizing can be confusing because different countries use different systems: Metric (millimeters), US Letter sizes, and older UK number sizes. Use our quick reference guide to pick the exact tool for your pattern.

1. Universal Hook Size Conversion Chart

Metric (mm) US Letter Best Yarn Weight Common Projects
2.25 mm – 2.75 mm B/1 to C/2 Fingering / Sport Miniature amigurumi, keychains
3.00 mm – 3.75 mm D/3 to F/5 DK / Light Worsted Standard amigurumi, floral coasters
4.00 mm – 5.00 mm G/6 to H/8 Worsted (#4) Tote bags, wearables, blankets
5.50 mm – 6.50 mm I/9 to K/10.5 Bulky (#5) Cozy throws, chunky winter hats

2. The Amigurumi Sizing Rule

When making crochet stuffed toys, always size down your hook by 0.5mm to 1.0mm from the yarn manufacturer's recommended hook size. This creates compact, tight stitches that prevent polyester stuffing from poking through.

Find inspiration for your next project in our Pattern Catalog or browse our cozy Blanket Collection.