Katha or Biswa (also spelled kattha or cottah; Hindi: कट्ठा, Assamese: কঠা, Bengali: কাঠা) is a unit of area mostly used for land measurement in India, Nepal, and Bangladesh. After metrication in the mid-20th century by these countries, the unit became officially obsolete. But this unit is still in use in much of Bangladesh, Northern India, Eastern India and Nepal. The measurement of katha varies significantly from place to place.
In Purvanchal, 1 Katha = 1,361.25 square feet (126.464 m2) or 151.25 square yard. One Bigha is made up of 5 to 20 Katha. Katha is divided into 20 Dhur and Dhur is subdivided into 20 Dhurki.