Obi in martial arts

Many Japanese martial arts feature an obi as part of their exercise outfit. These obis are often made of thick cotton and are about 5 cm wide. The martial arts obis are most often worn in the koma-musubi knot (square knot); in practice where hakama is worn, the obi is tied in other ways.

In many martial arts the colour of the obi signifies the wearer's skill level. Usually the colours start from the beginner's white and end in the master's black, or red and white master belt.

Unlike in many other martial arts, adult practitioners of aikido do not wear coloured obis, though in some schools different colour codes have been formed, especially for children. The children's obis range from white for beginner level to 5th kyū, other colours for the rest of the kyū levels, and black for levels 1st dan and up.

In some aikido schools, wearing a hakama is a privilege earned by reaching the first dan level. In other schools, all practitioners may wear a hakama. After taking up using a hakama, the colour of obi does not matter since it will be covered by the hakama.

Below is a typical example of obi colours per level in aikido:

However, aikido schools worldwide may use their own systems with little reference to other schools save the use of a black belt for at least some dan grades.

Ninja obi are required to JNF or WNF.

The outfit used for Atarashii naginata practice includes a hakama that covers the obi. The obi is always white; its colour has no significance beyond simply blending in with the white keikogi worn when practicing the art.

The outfit worn to iaido practise includes a hakama, which is worn over the top of the obi, which fastens the keikogi. The obi colour has no meaning in iaido, and is usually chosen to blend in with the kimono or hakama worn by the practitioner.

The outfit used for jōdō practise includes a hakama that covers the obi. The colour of the obi has no significance.

Below are the colours of obis worn for judo practise. Junior practitioners have a different colour range. There are also other colour ranges used worldwide.

The colours for obis used for jujutsu practise range as follows:

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