When a dog is pregnant, you never know how many new arrivals to expect. Some bear lonely litters of single pups, while other size figures are in the double digits. You can't be sure without an ultrasound, but you can make an educated guess.
Litter Sizes on Average
If you take all types of dogs into consideration, litters average between 6 and 10 tiny puppies, the Humane Society of Tampa Bay reports. This range is an average: Many mother dogs indeed bear fewer than six or more than 10 offspring in a single litter.
When guessing how many puppies a dog may have, look at her size. If she's a massive Bernese mountain dog, her litter may include up to 20 youngsters, the Humane Society of Utah says. If she's a diminutive Lhasa apso, however, the number is likely to be drastically lower -- anywhere from three to eight pups at once. A midsize pooch may be somewhere in between. But your dog may be exceptional. A Bernese mountain dog may produce a smaller litter than usual, and a Lhasa may have a larger one. Pomeranians are an example of a breed that typically produces tiny litters; golden retrievers usually have big ones.
Alternating Litter Size
Pregnancy can be physically taxing on bitches' physiques, using up minerals, proteins, energy and the like -- especially in cases of big litters. If a female dog previously gave birth to a sizable litter, her next might be a small one. If her previous litter was tiny, she might instead have a big bunch this time around.
A mother dog's age is also a factor in litter size. If a bitch is barely past her puppy stage, she is more likely to have a tiny litter. This also applies to older female dogs -- those over 5 years old. If a dog is on the older side with her first-ever pregnancy, say 4 years or older, she also may have fewer puppies than the more youthful mamas.
If you're serious about knowing how many puppies your dog may have, your safest bet is to have a veterinarian conduct an ultrasound on the expectant mother. These scans can generally offer reliable numbers. Her bulging belly can't reveal too much from the outside, after all. A vet can feel for babies after a certain point in gestation, but don't try it yourself.