Crochet Hook Size Conversion Calculator
Created by: Emma Collins
Last updated:
Convert crochet hook sizes between US, UK, and metric (mm) systems instantly. Whether you're following an international pattern or need to find the right hook from your collection, this converter helps you match hook sizes accurately.
Crochet Hook Size Conversion Calculator
CrochetConvert hook sizes between US, UK, and metric systems
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What is a Crochet Hook Size Conversion Calculator?
A Crochet Hook Size Conversion Calculator helps you convert between US, UK, and metric (mm) crochet hook sizes. Since patterns from different countries use different sizing systems, this tool ensures you always use the correct hook for your project.
The metric measurement (millimeters) is the universal standard for hook sizing. This calculator provides instant conversions so you can work with patterns from any country or match hooks from your collection to pattern requirements.
Understanding Crochet Hook Sizes
Metric (mm): The universal standard measurement - always accurate
US Sizes: Letter-number combinations (B/1 through S)
UK/Canadian: Numbered system, different from US numbers
Steel Hooks: Separate sizing for thread crochet (sizes 00-14)
Frequently Asked Questions
What is the difference between US and UK crochet hook sizes?
US and UK crochet hook sizing systems use different numbers for the same hook. US sizes are typically numbered (like B/1, C/2, D/3), while UK sizes use different numbers. The metric (mm) measurement is the universal standard that both systems reference.
How do I know which crochet hook size to use?
Check your pattern for the recommended hook size and gauge. Make a gauge swatch with the suggested hook, then adjust up or down if your stitches are too tight or loose. The yarn label also suggests hook size ranges.
What is the most common crochet hook size?
A 5.0mm (US H/8, UK 6) hook is one of the most versatile sizes, working well with worsted weight yarn. For beginners, starting with a 5.0-5.5mm hook and medium weight yarn is recommended for easier stitch visibility.
Are steel crochet hooks sized differently?
Yes, steel crochet hooks (used for thread crochet and fine lace) have their own sizing system. Steel hook numbers run opposite to regular hooks - higher numbers mean smaller hooks. A steel size 7 is smaller than a steel size 1.
Can I substitute a different hook size than the pattern calls for?
Yes, but you must make a gauge swatch. If your gauge matches the pattern with a different hook size, that's your correct hook. Going up a hook size creates looser fabric; going down creates tighter, denser fabric.
What do the letters mean in US crochet hook sizes?
US hooks use letters (B through S) alongside numbers. B/1 is the smallest regular hook (2.25mm), progressing to larger sizes like S (19mm). The letter system predates standardization, which is why metric measurements are most reliable.
How do I convert between crochet hook and knitting needle sizes?
Crochet hooks and knitting needles of the same mm size are equivalent in diameter. A 5.0mm crochet hook equals a US 8 knitting needle. However, crochet typically uses one hook size larger than knitting for the same yarn weight.
Sources and References
- Craft Yarn Council, "Standard Hook Size Charts", 2024
- The Crochet Guild of America, "Hook Size Guide"
- Ravelry.com, "International Hook Size Reference"