Karate uniform sizes are standardised throughout the industry. They're labelled by number, with lower numbers smaller than higher numbers. This numbering system corresponds with no other sizing system in the world. It takes time and practice before you can simply eye a person and know what size they need. However, two quick measurements will tell you exactly which number to get for yourself or your family.
Though there will be some small differences in cut between manufacturers, these guidelines should work for all major karate uniform brands.
Check your height with a tape measure. The specific size you need will depend on height.
Check your weight on a bathroom scale. The specific size you need will also depend on weight.
Use the following chart to determine your approximate size:
Children: 3ft, 0 inches = 13.6 Kilogram = size 000 3ft, 5 inches = 18.1 Kilogram = size 00 3ft, 10 inches= 24.9 Kilogram = size 0
Youth: 4ft, 3 inches =31.8 Kilogram = size 1 4ft, 8 inches= 40.8 Kilogram= size 2 5ft, 1 inch = 49.9 Kilogram = size 3
Adults: 5ft, 6 inches = 63.5 Kilogram = size 4 5ft, 11 inches = 77.1 Kilogram = size 5 6ft, 2 inches = 90.7 Kilogram = size 6 6ft, 5 inches = 104 Kilogram = size 7
If your height and weight are in different categories, go with height. Karate uniforms are designed to fit loosely. If your height and weight are in different, but not adjacent, categories try splitting the difference. For example, if your height is size 4 but your weight is size 6, try on a size 5.
The difference between two sizes of gi is pretty significant. If a size 5 is slightly too small, then a size 6 will be much too big. If buying a gi for your child, always err on the side of too large. Hem in the legs and sleeves, then let them out. Also, never buy premium gis for children. They'll outgrow even a lightweight gi before they wear it out.