Achievement in Judo is recognised by a series of ranks or grades. The student ranks are called kyu and are usually differentiated by colored belts (obi). Different colors may be used around the world and in some countries there are more than 6 kyu ranks. The ten black belt, or expert, ranks are called dan. The traditional Judo ranks are:

        English                 Japanese

        6th grade               rokyu
        5th grade               gokyu
        4th grade               yonkyu
        3rd grade               sankyu
        2nd grade               nikyu
        1st grade               ikkyu

        1st degree              shodan
        2nd degree              nidan
        3rd degree              sandan
        4th degree              yodan
        5th degree              godan
        6th degree              rokudan
        7th degree              shichidan
        8th degree              hachidan
        9th degree              kudan
        10th degree             judan

In the days before Kano created Judo, there was no kyu/dan ranking system in the martial arts. A more traditional method of recognizing achievement was the presentation of certificates or scrolls, often with the secrets of the school inscribed. Kano started the modern rank system when he awarded shodan to two of his senior students (Shiro Saigo and Tsunejiro Tomita) in 1883. Even then, there was no external differentiation between yudansha (black belt ranks) and mudansha (those who hadn't yet attained black belt ranking). Kano apparently began the custom of having his yudansha wear black obi (belts) in 1886. These obi weren't the belts karateka and judoka wear today -- Kano hadn't invented the judogi (Judo uniform) yet, and his students were still practicing in kimono. They were the wide obi still worn with formal kimono. In 1907, Kano introduced the modern judogi and its modern obi, but he still only used white and black belt ranks.

Around 1930 Jigoro Kano created a new belt to recognize the special achievements of high ranking black belts. Other arts such as the tea ceremony and swordsmanship provided recognition for their masters in the form of a special tea pot or sword. Jigoro Kano chose to recognize sixth, seventh, and eighth degree black belts with a special obi made of alternating red and white panels. The white color was chosen for purity, and red for the intense desire to train and the sacrifices made. The colors red and white are an enduring symbol of Japan, and they have been used in Judo since Jigoro Kano started the first Red and White Tournament in 1884. He also created the red belt to recognize 9th and 10th dans.