the tin of formula should say it on the side, but they should be having around 6 feeds a day, usually every 3 to 4hrs, around 150ml each feed. but as a child health nurse said to me, if they sleep through the night, they may have more feeds through the day to make up for it.
Usually try to do 3 to 4 hourly feeds, dependent on if they are sleeping thru the night. If you times body weight by 150ml / feeds per day gives you the required amount.
eg 6kg x 150 = 900ml total for the day / 6 (4hr feeds) = 150ml
or if 3hr / 8 = 112.5
The health nurse can also calculate it as well but the equation above is what most of them run off, unless the childs under weight/prem and the 150ml is changed to 200ml.
It depends on the formula & the baby. My LO was on formula from 2 weeks and was on 120ml. Sometimes at night she would even have more. It was more then what the time said but she needed it. She is only a small baby but loved her food smile a baby will stop eating when full so don't stress. My midwife told me that if my LO finished the 120ml bottle to the end them always offer more. Hope this helps