There is no normal litter size for puppies. Usually, the size of a dog litter is mainly based on the size of the dog's body simply because biologically, larger bodies are capable of carrying a larger litter than smaller bodies. The size of the litter also depends on the breed of the female. Typical litter size tends to range from 1 to 12 puppies, with an average of 5 to 6 puppies in all dogs.
However, large breeds can have up to 15 offspring. It's a wide range and depends on your dog's species, size, health, and pregnancy history. Breeders will tell you that they have larger litters if x, smaller litters if y, that they will never mate with a dog if z. Towards the end of your dog's pregnancy, your veterinarian will likely be able to feel the mother's belly or take an X-ray to determine an “exact number of puppies in their belly” (although it can be easy to miss one of the puppies, so you'll never know for sure until the little wiggles start coming out).
In general, large dogs have larger litters because, biologically, they can safely carry more puppies. The first four to five litters of a female dog are generally larger than the litters produced after the fifth brood. The smaller a dog's gene pool, the smaller its litters tend to be; on the contrary, dogs that come from more diverse backgrounds tend to have larger litters. Most of the time, evolutionary pressures result in the litter size most appropriate to a species' life history and survival strategy.
Doing so is very hard on the mother's body, and many believe it will result in a decrease in the total number of puppies produced by a dog over the course of its life. For example, dogs of breeds that normally produce litters of five puppies can only produce one or two for their first litter. As a general trend, the maximum litter size generally coincides with the total number of teats present, however, the average litter size is usually about half the number of available teats. So, while Pomeranian litters are likely to be much smaller than those of a wolf dog, Pomerania will have the opportunity to produce many more litters throughout its life.
While dogs can produce quite a few litters throughout their lives, it's important to realize that every pregnancy affects the health of dogs. Dogs fall somewhere between these two ends of the spectrum, since the average litter size across all breeds is approximately five. On the other hand, although larger dog breeds are capable of carrying larger litters, and often do, sizing alone does not guarantee a large litter. In general, smaller dog breeds have smaller litters because their body size does not allow them to carry large litters.
And, every time a dog becomes pregnant, she is more likely to have even more puppies with the next calf. According to the American Kennel Club, litters born in spring are generally larger than litters born at other times of the year.