Crochet hooks in different sizes and colors, arranged in a cup on a table

The Ultimate Guide to Crochet Hook Sizes: Comparing Metric, US, and UK Measurements

Introduction to Crochet Hooks

As a crocheter, you know that the right hook can make all the difference in your project. But with so many different crochet hook size systems, it can take time to figure out which hook is the right one for your project.

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Different Crochet Hook Size Systems

  • In the past, crochet hook sizes were typically measured in millimeters, with a range of sizes from small (2.0 mm) to large (25.0 mm). This system is still used in many countries worldwide, including Canada, Europe, and Australia.
  • In the United States, crochet hook sizes are measured using a different system. Instead of millimeters, US crochet hook sizes are measured using letters (A, B, C, etc.) and numbers (1, 2, 3, etc.), with sizes ranging from very small (size A-1, or 2.25 mm) to large (size Q, or 15.75 mm).

Comparing Crochet Hook Sizes

  • Comparing crochet hook sizes between these different systems can be confusing, especially if you're used to working with one system and trying to find a hook in another. 
    Crochet hooks in different sizes and colors, arranged in a cup on a table
  • That's where a crochet hook size conversion chart comes in handy! With a conversion chart, you can easily find the equivalent size hook in a different measurement system, allowing you to choose the right hook for your project no matter where you are.

The Size Chart

  • In the next section, we'll provide a handy crochet hook size conversion chart that you can use to compare metric, UK, and US sizes.


Metric Diameter (mm) US Letter US Number UK Number Recommended Yarn Weight
2.00 0 14 Super Fine (Sock, Fingering, Baby)
2.25 B 1 13 Super Fine (Sock, Fingering, Baby)
2.50 1,5 12 Super Fine (Sock, Fingering, Baby)
2.75 C 2 11 Super Fine (Sock, Fingering, Baby)
3.00 3 11 Super Fine (Sock, Fingering, Baby)
3.25 D 3 10

Super Fine (Sock, Fingering, Baby)

Fine (Sport, Baby)

3.50 E 4 9 Fine (Sport, Baby)
3.75 F 5

Fine (Sport, Baby)

Light (DK, Light Worsted)

4.00 G 6 8 Light (DK, Light Worsted)
4.25 G 6 Light (DK, Light Worsted)
4.50 7 7

Light (DK, Light Worsted)

Medium (Worsted, Afghan, Aran)

5.00 H 8 6 Medium (Worsted, Afghan, Aran)
5.50 I 9 5

Medium (Worsted, Afghan, Aran)

Bulky (Chunky, Craft, Rug)

6.00 J 10 4 Medium (Worsted, Afghan, Aran)
6.50 K 10,5 3 Medium (Worsted, Afghan, Aran)
7.00 Bulky (Chunky, Craft, Rug)
8.00 L 11 0

Bulky (Chunky, Craft, Rug)

Super Bulky (Bulky, Roving)

9.00 M 13 00 Super Bulky (Bulky, Roving)
10.00 N 15 000 Super Bulky (Bulky, Roving)
11.50 P 16 Super Bulky (Bulky, Roving)
12.75 17

Super Bulky (Bulky, Roving)

Jumbo (Jumbo, Roving)

15.00 P/Q 19 Jumbo (Jumbo, Roving)
16.00 Q Jumbo (Jumbo, Roving)
19.00 S 35 Jumbo (Jumbo, Roving)
25.00 U 50 Jumbo (Jumbo, Roving)


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