The best way to really tell is by feeling your dog. Until you have some experience with it you can ask a dog trainer, groomer, breeder or your vet for some help... just let them know you want an honest answer and don't take it personally if they say your dog is a little on the heavy or light side. I have had a lot of people ask but then be a little hurt when I have to tell them. I have also had groomers and vets tell me they wont tell someone when their dog is overweight because the risk that they will loose that person's business is to high.

The good thing is that with a little practice it is fairly easy to tell if your dog is within a good weight range. When you feel your dog you should be able to easily find their ribs but not their hip bones as easily. This will greatly depend on the dogs breed, with some breeds like Italian greyhounds and Vizsla you should be able to see their ribs but with a pug you shouldn't. What I typically ask people to try is feeling their own ribs and paying attention to if they can easily find them to count them. Think about your physical health and then compare how that feels to how their dogs ribs feel. Another good rule of thumb is to feel the back of your hand, that is about what your dog's rib cage should feel like.

For puppies it can be a little harder because when they are very young they have less muscle tone so expect them to feel a little more ribby than an adult. Also because their needs change as they go through periods of growth. The directions on the bag are just a VERY rough guideline. For example, I have three dogs that are between 38 and 44 LBS and one eats half of what the other two eat... she has a different energy level and just processes the food differently just like people do. Many puppies also go through periods where they don't really want to eat as much as they used to. This can mean that they are teething and it isn't comfortable to eat dry kibble or it can mean they just need less food because their growing art a different rate. If this happens add a little water to the food and let it get just a little soft to see if they eat better. If they do then it's probably just sore gums from teething.

In my experience, most pet dogs are overweight but that may or may not hold true outside of the US. So, even though your question didn't specifically ask about the risks...Overweight puppies can grow faster than they are really supposed to and this can cause structure issues and injuries in adulthood. Overweight adult dogs will have shorter life spans because they are prone to issues like hip dysplasia and diabetes. If you have an overweight dog you also have to be careful not to suddenly take them on long hikes or other activities that they are not physically fit enough to do or you will risk injury.

The best way to really tell is by feeling your dog. Until you have some experience with it you can ask a dog trainer, groomer, breeder or your vet for some help... just let them know you want an honest answer and don't take it personally if they say your dog is a little on the heavy or light side. I have had a lot of people ask but then be a little hurt when I have to tell them. I have also had groomers and vets tell me they wont tell someone when their dog is overweight because the risk that they will loose that person's business is to high.

The good thing is that with a little practice it is fairly easy to tell if your dog is within a good weight range. When you feel your dog you should be able to easily find their ribs but not their hip bones as easily. This will greatly depend on the dogs breed, with some breeds like Italian greyhounds and Vizsla you should be able to see their ribs but with a pug you shouldn't. What I typically ask people to try is feeling their own ribs and paying attention to if they can easily find them to count them. Think about your physical health and then compare how that feels to how their dogs ribs feel. Another good rule of thumb is to feel the back of your hand, that is about what your dog's rib cage should feel like.

It can also be helpful to look at images of dogs. You should see a well defined waist but you should not see hip bones. Like I said earlier for some breeds you should also see ribs. It sounds like you have a breed that will be easier to judge by feel than looks though.

For puppies it can be a little harder because when they are very young they have less muscle tone so at times they will feel a little more ribby than an adult or a little more "plush" if they are just about to go through a growth spirt. Their needs change as they go through periods of growth. The directions on the bag are just a VERY rough guideline. For example, I have three dogs that are between 38 and 44 LBS and one eats half of what the other two eat... she has a different energy level and just processes the food differently just like people do. 

Many puppies also go through periods where they don't really want to eat as much as they used to. This can mean that they are teething and it isn't comfortable to eat dry kibble or it can mean they just need less food because their growing at a different rate. If this happens, add a little water to the food and let it get just a little soft to see if they eat better. If they do then it's probably just sore gums from teething.

In my experience, most pet dogs are overweight but that may or may not hold true outside of the US. So, even though your question didn't specifically ask about the risks...Overweight puppies can grow faster than they are really supposed to and this can cause structure issues and injuries in adulthood. Overweight adult dogs will have shorter life spans because they are prone to issues like hip dysplasia and diabetes. If you have an overweight dog you also have to be careful not to suddenly take them on long hikes or other activities that they are not physically fit enough to do or you will risk injury.