There is no single answer — every baby is different. A general rule: babies need about 150ml of formula per kg of body weight per day in the first 6 months.
Feeding guide by age: First weeks: 60-90ml every 2-3 hours. By 2 months: 120-150ml every 3-4 hours. By 6 months: 180-240ml, 4-5 times per day.
Signs of adequate intake: 6 or more wet diapers per day, steady weight gain, alert and content between feeds.