Either breast milk or formula can easily be the sole source of nutrition during the first four to six months of life until that time when one tends to start solids. With solids introduced and being given in increasing amounts during the second half of the first year of life (as you describe), the amount of formula may vary. Infants around this age will take roughly six to eight ounces per feed about four or five times a day.
Each infant is unique, so I never recommend a minimum amount. It is also unusual for your baby to need much more than a quart (32 ounces) of formula in any given day. Babies are usually thirsty, and may prefer sweet-tasting juices that have less nutritional value. However, we wouldn't want to fill them up with empty calories. Everyone needs some liquids each day, but it's the nutritional value of either breast milk or formula that is most important.