Most Beagles should be given between one and one and a half cups of dog food twice per day. This is dependent on the dog as like humans they have different metabolic rates, nutrition levels and activity levels.
Most beagles should eat about 1 to 1 1/2 cups of dog food twice a day. A test to let you know if you need to reduce or increase the amount is to pinch the dogs skin with your finger and thumb. If you feel fat reduce the amount.
It depends on the calorie/fat content of the food. Almost all bagged dog food specifies the amount of food you should give your pet based on the pet's age and weight.
Canned food has a higher water content, thus more is required. Dry food varies greatly, depending on the content. Fillers such as corn gluten meal don't have nutritional value and you will have to feed more.