Ask your vet. Ours did a calorie calculator for us every time my puppy went in for shots and was weighed. Then I would check that against the Cal per cup according to the bag of kibble and often find he needed an increase. It was helpful.
The amount you need to feed depends a lot on the food you are feeding. There should be a chart on the bag that can give you a starting point. I use the suggestion on the bag and then adjust based on body condition. You want them to be lean as they grow, and slow growth is better for larger breed dogs. My 13 week old has gained about 2 to 3 pounds a week since he came home at 8 weeks old. He currently gets about a cup and a half of Fromm LBP Gold and 3/4 of a cup of Orijen per day split into 3 meals.