Unfortunately, the answer is not a simple one size fits all number. Depending on your dog's breed, current age, health, and daily surroundings, the amount of exercise varies. All dogs should exercise their body everyday for one to three hours through walking, running, or playing to maintain a healthy weight. Ideally, this exercise will be split up throughout the day, but with hectic work schedules or extreme weather conditions, that may not be feasible. For smaller dogs a few 10 minute walks or intense inside fetch game might be better than a long hour walk. For larger dogs, ten minutes of running followed by 20 minutes of walking is a good starting point. Breeds like Collies, Labradors, and Shepherds need even more exercise and do well with exercise that incorporates tricks. When it comes to learning new tricks this is the one thing that is the same for all dogs, they all need at least an hour of play time with their master to stimulate their brains and deter them from negative behaviors. This play can be done indoors or outdoors and should vary once in awhile to keep your dog's brain stimulated. The play can even involve the puppy parent standing still, but the dog should be moving as much as possible.
Having owned several Labrador Retrievers and currently owning a Collie/ Lab mix, I can tell you firsthand getting the right amount of play and exercise in everyday can make a huge difference in your dog's behavior and overall health. One new way to keep track of my dog's activity is with the Purina Pro5 app. This free app lets me track all kinds of activity and even set activity goals for all my pets. Another great way to stick with keeping active is to do specific activities with your dog at the same time everyday. Your dog will get into the routine and be reminding you each day when it is time to be active. Although there is no magic amount of exercise dogs need, it is important to make sure you and your dog stay active every day to help keep your dog healthy and continue to help you and your dog maintain a strong bond.