Koi judging in Japan is based on the 50-30-20 rule and includes the three basic topics, including 50% conformation, 30% quality, and 20% pattern, followed by standards within each variety.

When purchasing Koi for show you may want to base your choice on these topics as this is how shows are judged. Those purchasing Koi for pleasure will also find satisfaction using these topics as a guide in the selection of pleasing and healthy Koi.  

Conformation is the appropriate body shape, proportions, finnage, head shape, spacing and can include the ability to emanate power.

Quality is seen in many ways including skin, skin texture, depth of color and shine.

Pattern should be balanced side to side and front to back, as well as rules within varieties.

This is just the tip of the iceberg on each of these topics and and each one is very indepth and requires high standards when it comes down to selection of a Koi to show and in judging of Koi at shows. If you have the opportunity, attend a local Koi club show and follow the judges around as they do the judging, it will be a great learning  experience.