As a general guide feeding amounts are given on packs of dog food. However, they are just that - a guide. Every dog is an individual and some need more calories than others. Lifestage and lifestyle will have an impact on the amount of food an individual dog would need to eat to maintain their bodyweight.
First of all establish your dog's current body condition - is he over or under weight? The best way to do this is body condition scoring by checking for fat over the ribs and around the waist and belly. If your dog is overweight feed less than the feeding recommendations on pack, if underweight start off by feeding more.
Every week re-assess your dog and adjust feeding amounts up or down, depending on how close they are to the 'ideal' body weight and condition. Keep in mind that if your dog starts getting more exercise he will need more food and if he starts to spend more time indoors and exercises less, feeding amounts will need to be adjusted back down again.
By Libby Sheridan (Hills Pet Nutrition) (Professional Advisor)