Crochet hooks are sized by the diameter of the shaft.
The larger sizes are made of aluminum or plastic. That material is not strong enough for the smaller sizes, sometimes called “thread hooks”, which are made of steel.
Today in most of the world, crochet hooks are sized directly in millimeters. In the UK and Japan, for example, the larger sizes run 10, 9, 8, 7, 6.5, 6, 5.5, 5, 4.5, 4, 3.75, 3.50, 3, 2.5, and 2 millimeters. At that point the small size forces a switch to steel in the series 2.10, 1.75, 1.50, 1.25, 1.00, 0.90, 0.75, 0.50 millimeter.
| Old UK |
United States | Millimeters | ||
|---|---|---|---|---|
| Number | Letter plus number | letter | ||
| 1.25 | ||||
| 1.5 | ||||
| 14 | 2 | |||
| 4 | ||||
| 13 | 3 | B-1 | 2.25 | |
| 12 | C | 2.5 | ||
| 11 | 2 | C-2 | 2.75 | |
| D | 3 | |||
| D | 3.125 | |||
| 10 | 1 | D-3 | 3.25 | |
| 9 | 0 | E-4 | E | 3.5 |
| 00 | F-5 | 3.75 | ||
| 8 | F-5, G-6 | F | 4 | |
| G-6 | G | 4.25 | ||
| 7 | 7 | 4.5 | ||
| 6 | H-8 | H | 5 | |
| I | 5.25 | |||
| 5 | I-9 | 5.50 | ||
| J | 5.75 | |||
| 4 | J-10 | 6 | ||
| 3 | K-10½ | 6.5 | ||
| 2 | 7 | |||
| K | 7.5 | |||
| 0 | L-11 | 8 | ||
| 00 | M/N-13, N-13 | 9 | ||
| 000 | N/P-15, P-15 | 10 | ||
| P-16 | 11.50 | |||
| 17 | 12 | |||
| 12.75 | ||||
| 19 | P/Q | 15 | ||
| Q-19 | Q | 15.75 | ||
| Q | 16 | |||
| S-35 | S | 19 | ||
| T/U/X | 25 | |||
| T/X | 30 | |||
Five-inch long steel crochet hooks are sized from number 00, the largest, to number 15, the smallest. Steel hooks are usually used with cotton thread, rather than yarn; size 15 is capable of use with #250 thread.
During the 19th century, the United States imported steel crochet hooks from England and Germany. The Boye Needle Company, in Chicago, began to manufacture complete sets of steel hooks in sizes 1 to 14 in 1907.
| USA | Old UK |
millimeters | Comments |
|---|---|---|---|
| 15 | Boye introduced this size in Nov. 1924¹. | ||
| 14 | 6 | 0.6 | |
| 13 | 0.75 | ||
| 12 | 5 | 0.70 | |
| 11 | 0.8 | ||
| 10 | 4 | 1 | |
| 9 | 1.15 | ||
| 8 | 3 | 1.25 | |
| 7 | 2½ | 1.50 | |
| 6 | 1.6 | ||
| 5 | 1.7 | ||
| 4 | 2 | 1.75 | |
| 3 | 1.85 | ||
| 2 | 1.95 | ||
| 1 | 1 | 2 | |
| 0 | 00 | 2.25 | Boye introduced this size in Dec. 1924¹ |
| 00 | 3 | Boye introduced this size in Dec. 1924¹ |
1. Boye history from Sylvia Ourada through Nancy Nehring.
Bone hooks are 4½ or 5 inches long and made in sizes 1 through 6.
Afghan hooks are distinguished by a lack of a flat finger grip.
Wooden hooks are 9" or 10" long, and come in sizes from 7 through 16.
Good crochet-hooks are of the utmost importance in forming nice even work. They should be very smooth and selected of a size suited to the material to be worked. Crochet and tricot hooks are made of steel for fine work, and of ivory, bone, wood, and vulcanite for coarse work. They should be measured like a knitting-pin, by inserting them in the round hole of a gauge. For measuring hooks we use Walker's bell gauge.
The Young Ladies Journal Complete Guide to the Work-Table containing instructions in Berlin Work, Crochet, Drawn-Thread Work, Embroidery, Knitting, Knotting or Macrame, Lace, Netting, Poonah Painting and Tatting.
London: E. Harrison, 1884.
Page 11.
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Last revised: 20 May 2018.