Crochet Hook Size Converter
Convert between US, UK, metric and other international hook sizing systems
Tip: Enter a value in any field to see instant conversions across all systems.
Health Disclaimer: Extended periods of crocheting can potentially cause repetitive strain injuries. Please take regular breaks (15 minutes every hour), stretch your hands and wrists, and consider using ergonomic hooks. If you experience persistent pain or numbness in your hands, wrists, or arms, please consult a healthcare professional.
Conversion Results
Metric (mm):
US Size:
UK Size:
Japanese Size:
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Recommended For:
This hook size is commonly used for medium weight yarn projects like scarves and blankets.
Hook Material Suggestion:
For this size, aluminum hooks offer good durability and smooth stitching.
Understanding Crochet Hook Sizing Systems
Metric System
The metric system measures hook size in millimeters (mm) based on the diameter of the shaft. This is the most precise and universal system used internationally. Sizes typically range from 0.6mm (extremely fine) to 25mm (jumbo).
US System
The US uses a combination of letters and numbers. Steel hooks use numbers (higher number = smaller hook), while larger hooks use letters (A-S). The system isn't perfectly consistent, which makes conversion tools essential.
UK System
The UK system uses numbers running opposite to the US number system. In the UK system, larger numbers indicate smaller hooks (14 is tiny, while 000 is quite large). This inverse relationship can be confusing when reading international patterns.
Japanese System
The Japanese system uses numbers that roughly correspond to millimeter sizes, though not exactly. Japanese hooks are particularly popular for amigurumi and fine work due to their precision engineering.
"Using the correct hook size is crucial for achieving proper tension and stitch definition. Our converter helps you navigate different international sizing systems with confidence."
Crochet Hook Materials & Their Benefits
Aluminum/Metal
Lightweight and durable, metal hooks provide smooth stitching with less friction. The slick surface allows yarn to glide easily, making them ideal for speed crocheters. Best for plant-based fibers like cotton and bamboo.
Wooden/Bamboo
Warmer to the touch and slightly "grippier" than metal, wooden hooks are excellent for slippery yarns like silk or mohair. They reduce hand fatigue during long sessions and are often preferred by those with joint pain.
Plastic/Acrylic
Lightweight and economical, plastic hooks are great for beginners. They come in vibrant colors and larger sizes that might be costly in other materials. Some are even ergonomically designed to reduce hand strain.
Ergonomic Handles
Many hooks now feature specialized grips or handles to reduce strain and make crocheting more comfortable. These hybrid designs often combine materials, with a metal hook and a cushioned handle for extended crafting sessions.
Pro Tip: If you're experiencing hand pain while crocheting, try switching to a different hook material. Many crocheters find that wooden hooks put less strain on joints compared to metal ones.
Frequently Asked Questions
Why do crochet patterns specify particular hook sizes?
Hook sizes directly affect gauge (the number of stitches and rows per inch). Using the specified hook helps ensure your finished project will have the intended dimensions. However, always check your gauge and adjust hook size if needed to match the pattern's gauge requirements.
Are crochet hook sizes standardized internationally?
Only the metric (mm) measurements are truly standardized. The letter/number designations can vary slightly between manufacturers and countries. This is why our converter focuses on the mm size as the most reliable reference point for conversions between systems.
What if my pattern doesn't specify which sizing system it's using?
Check the pattern's origin. US patterns typically use letters for larger hooks and numbers for steel hooks. UK patterns use numbers exclusively. When in doubt, look for any metric equivalents mentioned, or check if the pattern specifies yarn weight, which can help you make an educated guess about appropriate hook size.
How much does hook size affect my finished project?
Hook size has a significant impact. A smaller hook creates tighter, firmer fabric with less drape, while a larger hook produces looser, more open work with more flexibility. Even a 0.5mm difference can change the size of a garment by several inches or affect the stiffness of amigurumi projects.
What if I can't find the exact hook size my pattern calls for?
Use the closest size available and check your gauge. You might need to adjust your tension (how tightly you crochet) to compensate. Our converter helps you find the closest equivalent in different sizing systems, giving you more options to work with.