Karate belt numbers such as 0, 1, 2, and 3 describe the belt’s size; higher numbers generally mean a longer belt. These sizing numbers are separate from rank, and there is no reliable age-to-size conversion. Children and adults may wear the same size depending on their waist measurement. Sizes also vary by manufacturer, so use the chart for the exact belt you are buying.
Measure around your waist where the belt will sit, ideally over your uniform, or measure a belt that already fits. A traditional double-wrap belt goes around the waist twice before it is tied. In the Century example below, a 25–28-inch waist corresponds to size 3, while a 23–24-inch waist corresponds to size 2. This chart allows approximately 12-inch ends after tying; check your instructor’s preferred fit and the seller’s chart before ordering.
Double-wrap belt size chart
| Size | Waist (inches) | Belt length |
|---|---|---|
| 0 | Up to 20″ | 85″ / 216 cm |
| 1 | 21–22″ | 88″ / 224 cm |
| 2 | 23–24″ | 92″ / 234 cm |
| 3 | 25–28″ | 96″ / 244 cm |
| 4 | 29–32″ | 104″ / 264 cm |
| 5 | 33–36″ | 112″ / 284 cm |
| 6 | 37–40″ | 120″ / 305 cm |
| 7 | 41–45″ | 130″ / 330 cm |
| 8 | 46–50″ | 140″ / 356 cm |
| 9 | 51–55″ | 150″ / 381 cm |