Complete Crochet Hook Size Conversion Chart & Guide: US, UK, Metric & Japanese Standards

Introduction: Understanding Crochet Hook Sizing

Crochet hooks come in various sizing systems depending on the country of origin and manufacturer. This inconsistency can be confusing when following patterns from different regions or working with international yarn companies. This comprehensive guide provides easy-to-reference conversion charts and practical information to help you select the right hook for any project, regardless of which sizing system the pattern uses.

Core Crochet Hook Sizing Systems

Four main sizing systems are used globally for crochet hooks:

1. US System: Uses letters and numbers (B-1 through S)
2. UK/Canadian System: Uses numbers only (14 down to 0, then 00, 000, etc.)
3. Metric System: Uses millimeters (0.6mm to 20mm+)
4. Japanese System: Uses numbers (2/0 to 15)

The metric measurement (mm) is the most universal and precise reference point, as it directly indicates the hook’s diameter.

Master Conversion Chart: All Sizing Systems

Specialty Hook Sizes

Tunisian Crochet Hooks

Tunisian hooks are longer than standard hooks and often have a stopper at the end. They follow the same sizing systems but may be labeled as “Afghan hooks” or “Tunisian hooks.”

Double-ended Hooks

Used for Tunisian crochet in the round or for Cro-hooking (a technique combining crochet and knitting). These follow standard sizing systems.

Ergonomic and Specialty Hooks

These hooks may have modified handles but still use standard sizing systems for the hook head.

Hook Materials and Their Impact

Yarn Weight to Hook Size Recommendations

Using the appropriate hook size for your yarn is crucial for achieving the desired fabric texture and drape.

Common Challenges and Solutions

Challenge: Pattern Uses Different Sizing System

Solution:

• Always refer to the metric measurement when in doubt
• Use this conversion chart to find equivalent sizes
• When between sizes, check gauge or choose based on your tension (looser crocheters should size down)

Challenge: Hook Size Not Available

Solution:

• Substitute with closest available size
• Check gauge with the substitute hook
• Adjust pattern as needed based on gauge results

Challenge: Inconsistent Hook Sizing Between Brands

Solution:

• Measure hook diameter with a gauge tool
• Rely on the metric measurement rather than letter/number
• Test gauge before beginning project

Challenge: Achieving Correct Gauge

Solution:

• If gauge swatch is too tight, go up a hook size
• If gauge swatch is too loose, go down a hook size
• Change hook material if yarn is slipping or dragging

Best Practices for Hook Selection

Choosing the Right Hook for Your Project

1. Check pattern recommendations first
2. Consider yarn label suggestions as a starting point
3. Think about desired fabric texture:
   • Tighter fabric = smaller hook
   • Drapier fabric = larger hook
4. Factor in your personal tension:
   • Tight crocheters may need to size up
   • Loose crocheters may need to size down
5. Consider project type:
   • Amigurumi typically uses smaller hooks than yarn label suggests
   • Shawls and garments often use larger hooks for drape
   • Bags and baskets may use smaller hooks for structure

Storing and Organizing Your Hooks

• Label hooks with size if not already marked
• Store similar sizes together
• Consider color-coding by size range
• Use hook cases with labeled slots
• Keep conversion chart with your hooks

International Pattern Reading Tips

US Pattern Terminology

• Typically uses letter/number combination
• May list metric size in parentheses
• Look for “US Size” designation

UK Pattern Terminology

• Uses different number system (opposite direction from US)
• Often lists size as “No. 8” or similar
• Look for “UK Size” designation

Japanese Pattern Terminology

• Often uses charts with minimal text
• Hook size typically given in mm
• May use Japanese size numbers in some cases

International Symbol Patterns

• Most symbol crochet patterns include a hook size in mm
• Always check gauge information

Resources for Further Learning

Measuring Tools

• Hook gauge tools (physical)
• Digital calipers for precise measurement
• Printable hook sizers

Mobile Apps

• Crochet Hook Converter apps
• Gauge calculator apps
• Ravelry app (for pattern information)

Online Resources

• Craft Yarn Council standards
• Conversion calculators
• Video tutorials on gauge and hook selection

Books

• “The Crochet Stitch Handbook” by Betty Barnden
• “Crochet: The Complete Guide” by Jane Davis
• “Vogue Knitting: The Ultimate Crochet Book”

Final Tips

1. Always make a gauge swatch before starting a project
2. Keep this conversion chart in your crochet toolkit
3. When in doubt, go by the metric measurement
4. Label unmarked hooks with permanent marker or stickers
5. Consider having duplicate sizes in different materials for different yarns
6. Pay attention to how hook material affects your tension
7. Remember that the “right” hook is the one that gives you the fabric you want
8. Trust your hands – comfort during crocheting is important