A good chair is one which can be termed as ergonomic. An ergonomic chair supports the seven most important points in your body while you are seated.

These seven points are:

1. Upper back (thoracic)
2. Lower back (lumbar)
3. Sitting bones (ischial tuberosities)
4. Thigh behind the knee
5. Area behind the knee
6. Arms
7. Feet

OTHER SALIENT FEATURES OF A GOOD CHAIR :

A 3-D contoured backrest reaching right upto the shoulders with correct lumbar support.

A firm seat, which does not exceed two-thirds of the length of the thigh.

A seat arch with a slightly backward slope.

An armrest at an appropriate height.