The amount of BTC mined per day depends on the amount of mining power produced by a mining rig. The higher the mining hash rate, the more likely it is BTC block rewards will be found. The lower the mining hash rate, the less likely block rewards will be found. According to the CoinWarz profitability calculator, at the time of writing, a mining rig producing 120 TH/s would produce 0.00053550 BTC per day.