How many puppies do english mastiffs usually have? Asked By: Flavio Will. Date created: Sat, Nov 28, 2020 9:27 PM. Best answers. Mastiff Litter Sizes. A mastiff might give birth to only one puppy in a pregnancy, but litters of up to 16 puppies have been reported. In between these two extremes is the average litter size, which is about eight puppies. Answered By: Lora Schowalter. Date created: Sun, Nov 29, 2020 11:30 PM. FAQ. =I At what age do puppies get parvo shots? These will include ...