India uses over a dozen traditional land units alongside the metric Square Foot — Gunta and Cent in the south, Bigha and Katha in the east and north, Marla and Kanal in the northwest, and Ground in Tamil Nadu. Each grew out of local agricultural and revenue record-keeping, which is why they don't share a single national conversion factor.
Square Feet is the closest thing India has to a universal unit — it's understood in every state and is what this converter uses as its base. When in doubt, convert any regional unit to Square Feet first before comparing two properties, and always verify Bigha, Katha, or Biswa figures against your state's official land records, since these three vary the most.