A katha (also spelled kattha or cottah) is a unit of area in Nepal, Bangladesh and India approximately equal to 1/20 of a bigha.
This unit is still in use in much of Bangladesh and India, but the size varies significantly from place to place. In the Indian state of Bihar, one katha may vary from 750 ft² to 2000 ft². Also this can be 32 by 30 feet in length and breadth respectively.
In Assam 1 Katha is generally equal to 2880ft².
In north Bihar and Patna, 1 Katha is generally equal to 1360 ft². 20 Kathas equals 1 Bigha. One katha is further subdivided in 20 dhur. One dhur is further subdivided in 20 dhurki. 1 hectare= 2.5 acre approx or 4 bighas; 1 acre = 1.6 bighas or 32 kathas; 1 bigha = 20 kathas; 1 katha = 20 dhoor; 1 dhoor = 6.25 ya 6.5 haath; 1 katha = 1.65 decimal.
1 decimal in Bihar equals to 435.56 sq feet.
In Bangladesh, one katha is standardized to 720 square feet (67 m2), and 20 katha equals 1 bigha.
The Katha is still in use in Nepal, where it is equivalent to 338.57 m² (3,644.3 ft²).[.