Assuming you have an Antminer S9, which is currently the most efficient Bitcoin miner on the market, you can expect to mine about 0.14 BTC per day. This assumes that the Bitcoin network difficulty remains the same and that the price of Bitcoin stays the same. If either of these two things change, your mining profitability will change with it.
For example, if the Bitcoin network difficulty increases, you will mine fewer BTC per day. And if the price of Bitcoin falls, you will also mine fewer BTC per day. However, if the price of Bitcoin rises, you will mine more BTC per day.
In conclusion, you can expect to mine about 0.14 BTC per day with an Antminer S9.
This number can change depending on the current difficulty of the Bitcoin network and the price of Bitcoin.