We gave Castor food three times a day until he was like eight or nine months old, and after that two times per day. When it comes to level of activity, bulldogs are not high energy dogs, but puppies are supposed to eat quite a lot. We gave Castor puppy kibble (various brands, trying to find something that worked!) and we calculated the amount of food based on his age, weight (there were tables on the bags). When we tranistioned him to adult food (at seven months, perhaps - don't remember), the recommendations were to aim at target weight. Castor's tummy couldn't take the suggested portions, though, so we always fed him less. When he was about a year, we changed to raw feeding and now we can give him much more food and he has filled out a bit.
The bottom line is that you will notice how much food your dog needs - loose stool can mean that he gets too much food (i.e. more food than his tummy can take), for instance.