Inches |
CM |
14" |
35.6 |
15" |
38.1 |
16" |
40.6 |
17" |
43.2 |
18" |
45.7 |
19" |
48.3 |
20" |
50.8 |
21" |
53.3 |
22" |
55.9 |
23" |
58.4 |
24" |
61 |
26" |
66 |
28" |
71.1 |
30" |
76.2 |
Inches |
CM |
6" |
15.2 |
6.5" |
16.5 |
7" |
17.7 |
7.5" |
19 |
8" |
20.3 |
8.5" |
21.6 |
9" |
22.8 |
| Inside Diameter (mm) |
inside Circumference |
United States & Canada |
UK, Europe and Australia |
Asia |
| 14.88 | 46.8 | 4 | H | 7 |
| 15.09 | 47.4 | 4¼ | H½ | |
| 15.29 | 48 | 4½ | I | 8 |
| 15.49 | 48.7 | 4¾ | J | |
| 15.7 | 49.3 | 5 | J½ | 9 |
| 15.9 | 50 | 5¼ | K | |
| 16.1 | 50.6 | 5½ | K½ | 10 |
| 16.31 | 51.2 | 5¾ | L | |
| 16.51 | 51.9 | 6 | L½ | 11 |
| 16.71 | 52.5 | 6¼ | M | 12 |
| 16.92 | 53.1 | 6½ | M½ | 13 |
| 17.12 | 53.8 | 6¾ | N | |
| 17.32 | 54.4 | 7 | N½ | 14 |
| 17.53 | 55.1 | 7¼ | O | |
| 17.73 | 55.7 | 7½ | O½ | 15 |
| 17.93 | 56.3 | 7¾ | P | |
| 18.14 | 57 | 8 | P½ | 16 |
| 18.34 | 57.6 | 8¼ | Q | |
| 18.54 | 58.3 | 8½ | Q½ | 17 |
| 18.75 | 58.9 | 8¾ | R | |
| 18.95 | 59.5 | 9 | R½ | 18 |
| 19.15 | 60.2 | 9¼ | S | |
| 19.35 | 60.8 | 9½ | S½ | 19 |
| 19.56 | 61.4 | 9¾ | T | |
| 19.76 | 62.1 | 10 | T½ | 20 |
| 19.96 | 62.7 | 10¼ | U | 21 |
| 20.17 | 63.4 | 10½ | U½ | 22 |
| 20.37 | 64 | 10¾ | V | |
| 20.57 | 64.6 | 11 | V½ | 23 |
| 20.78 | 65.3 | 11¼ | W | |
| 20.98 | 65.9 | 11½ | W½ | 24 |
| 21.18 | 66.6 | 11¾ | X | |
| 21.39 | 67.2 | 12 | X½ | 25 |
| 21.59 | 67.8 | 12¼ | Y | |
| 21.79 | 68.5 | 12½ | Z | 26 |
| 22 | 69.1 | 12¾ | Z½ | |
| 22.2 | 69.7 | 13 | 27 | |
| 22.4 | 70.4 | 13¼ | Z1 | |
| 22.61 | 71 | 13½ | ||
| 22.81 | 71.7 | 13¾ | Z2 | |
| 23.01 | 72.3 | 14 | Z3 |