In what price band a stock should trade within is decided by the exchanges.
Circuit Limit is calculated based on previous closing price of the security.
Eg, if stock ABC has price band of 10% and closes at 100, the next day Upper Circuit limit will be 110 and Lower Circuit Limit will be 90.
You can download the list of applicable price bands for each scrip from NSE website.
Though, you do not have to manually calculate them, the Circuit Limit are already displayed in Market Depth on Kite.
It is tough to sell a stock which is hitting Lower Circuit as there are only sellers and very less to none buyers.