Crochet Hook Size Chart: The Ultimate Metric, US & UK Conversion Reference

📅 Last updated: February 2026
Sarah Mitchell
CYC Certified Instructor · 20+ Years Crochet Experience

Written from two decades of hands-on crochet experience. Every recommendation in this guide has been tested with real yarn and real hooks. Reviewed for accuracy by Maria Gonzalez, 30-year fiber arts instructor.

✅ Fact-Checked📋 Editorial Standards

📋 Table of Contents

  1. Why Crochet Hook Sizes Are So Confusing
  2. Complete Crochet Hook Size Conversion Table
  3. Steel Crochet Hooks for Thread Crochet
  4. Which Hook Size for Which Yarn Weight
  5. Hook Materials and How They Affect Your Stitching
  6. Ergonomic Crochet Hooks
  7. FAQ

Why Crochet Hook Sizes Are So Confusing

If you've ever stared at a crochet pattern calling for a "UK size 9" hook and wondered whether that's the same as a US E/4 or a metric 3.5 mm, you're not alone. The confusion stems from three independent sizing systems that developed across different regions and eras, each using its own logic. The metric system measures hook diameter in millimeters — straightforward and universal. The US system assigns letters (and sometimes numbers) that progress alphabetically as hooks get larger. The UK/Canadian system uses numbers derived from the old Steelmaker's Wire Gauge, where confusingly, smaller numbers mean larger hooks.

To make matters worse, some older US patterns use only numbers (not letters), and the UK system has been largely discontinued by modern hook manufacturers in favor of metric sizing. Vintage patterns from the 1950s–1980s often reference UK sizes without metric equivalents, leaving modern crocheters scrambling for conversion charts. Our hook size converter tool eliminates this confusion entirely — enter any size in any system and see all three equivalents instantly.

The Craft Yarn Council has been working to standardize hook sizing around the metric system, and most hooks sold today display their millimeter size prominently on the handle. However, many popular patterns, tutorials, and social media posts still reference US letter sizes (especially in North American crochet communities), making a reliable conversion reference essential for every crocheter's toolkit.

Complete Crochet Hook Size Conversion Table (Metric, US, UK)

This comprehensive table includes all standard crochet hook sizes used worldwide. Sizes marked with "—" indicate that no equivalent exists in that particular system. The most commonly used sizes for general crochet projects are highlighted.

Metric (mm) US Size UK/Canadian Best Yarn Weight
2.0 mm B/1 14 Lace
2.25 mm B/1 13 Lace – Fingering
2.5 mm C/2 12 Fingering
2.75 mm C/2 12 Fingering
3.0 mm D/3 11 Fingering – Sport
3.25 mm D/3 10 Sport
3.5 mm E/4 9 Sport
3.75 mm F/5 9 Sport–DK
4.0 mm G/6 8 DK
4.5 mm 7 7 DK – Worsted
5.0 mm H/8 6 Worsted
5.5 mm I/9 5 Worsted
6.0 mm J/10 4 Worsted – Bulky
6.5 mm K/10½ 3 Bulky
7.0 mm — 2 Bulky
8.0 mm L/11 0 Bulky
9.0 mm M/13 00 Super Bulky
10.0 mm N/15 000 Super Bulky
11.5 mm P/16 — Super Bulky
15.0 mm Q — Jumbo
19.0 mm S — Jumbo
25.0 mm U — Jumbo

Steel Crochet Hooks for Thread Crochet

Steel crochet hooks are a separate category used exclusively for thread crochet — doilies, lace edgings, tablecloths, and other delicate work with crochet thread rather than yarn. Steel hooks are much smaller than standard aluminum or bamboo hooks, ranging from 0.6 mm to approximately 2.0 mm in diameter. They have their own numbering system where, confusingly, higher numbers indicate smaller hooks — the exact opposite of the standard hook numbering convention.

A steel size 1 hook is approximately 2.75 mm (relatively large for steel hooks), while a steel size 14 is a tiny 0.6 mm. Thread crochet is a specialized skill that requires excellent eyesight, fine motor control, and patience. It produces stunningly intricate lace work that has been prized for centuries. If you're interested in thread crochet, invest in a set of steel hooks and fine crochet thread (typically size 10 or size 3 thread).

Which Hook Size for Which Yarn Weight

The Craft Yarn Council publishes recommended hook size ranges for each yarn weight category. These recommendations provide a starting point, but your personal gauge may require adjusting up or down. The most reliable method is always to check the yarn label, which prints the recommended hook size for that specific yarn, and then make a gauge swatch to confirm.

💡 Pro Tip If you're between hook sizes and your yarn label recommends "5.0–6.0 mm," start with the middle size (5.5 mm) and adjust based on your gauge swatch. Going up creates a looser, more drapey fabric; going down creates a tighter, denser fabric. Neither is wrong — choose based on the fabric feel you want for your project.

Hook Materials and How They Affect Your Stitching

Aluminum: The most common and affordable option. Lightweight, smooth, and durable. Yarn glides quickly, making aluminum ideal for speed crocheters. Best with acrylic, cotton, and other non-slippery yarns. Available in all standard sizes from 2.0 mm to 25.0 mm.

Bamboo/Wood: Warmer to the touch, lighter than aluminum, and provides more friction against the yarn. Excellent for slippery fibers like silk, bamboo fiber, and mercerized cotton. The natural grip prevents stitches from sliding off accidentally. However, bamboo hooks can break if you crochet with very heavy tension.

Plastic/Resin: Very lightweight and affordable. Large plastic hooks (10 mm+) are significantly lighter than their aluminum equivalents, reducing hand fatigue for jumbo yarn projects. However, the surface can be slightly rougher, which may slow your yarn speed.

Ergonomic Crochet Hooks: Sizing and Selection Guide

Ergonomic hooks have revolutionized crochet comfort. They feature enlarged, cushioned handles (often made of rubber, silicone, or thermoplastic) that distribute pressure across a larger area of your hand, reducing strain on the thumb, index finger, and wrist. Brands like Clover Amour, Tulip Etimo, and Furls Odyssey have become bestsellers precisely because they allow crocheters to work for longer periods without pain or fatigue.

Ergonomic hooks use the same standard millimeter sizing as regular hooks — a 5.0 mm ergonomic hook produces the same gauge as a 5.0 mm aluminum hook. The difference is purely in the handle comfort. If you experience hand pain, cramping, or numbness while crocheting, switching to ergonomic hooks is one of the most effective interventions available. Many crocheters with arthritis, carpal tunnel syndrome, or repetitive strain injuries credit ergonomic hooks with allowing them to continue their craft pain-free.

Frequently Asked Questions

The 5.0 mm (US H/8) hook is the most commonly used size worldwide. It pairs with worsted weight yarn — the most popular yarn weight for blankets, hats, scarves, and general-purpose crochet projects. If you're buying your first hook, start with a 5.0 mm or 5.5 mm.
Worsted weight yarn (CYC #4) typically uses hooks in the 5.0–6.0 mm range (US H/8 to J/10). Check your specific yarn label for the recommended hook size, as different yarn brands and fiber contents can shift the ideal hook within this range.
The metric (mm) measurements are shared between crochet hooks and knitting needles — a 5.0 mm tool is 5.0 mm regardless of craft. However, the US numbering systems differ: knitting uses numbers only (US 8 = 5.0 mm) while crochet uses letters (US H/8 = 5.0 mm). Don't mix them up!

📚 Sources & References

  1. Craft Yarn Council — Standard Yarn Weight System
  2. Craft Yarn Council — How to Read Yarn Labels
  3. Edie Eckman — "The Crochet Answer Book" (Storey Publishing, 2nd Edition)
  4. Crochet Guild of America (CGOA) — Professional Development Resources

Related Resources

🪝 Hook Size Converter⚖️ Yarn Weight Chart📐 Gauge Guide