Why Do Small Dog Breeds Live Longer?

A common question among pet parents is why small dogs live longer than big dogs? In reality, does size really matter when it comes to the average lifespan of a dog? The short answer to this question is yes, dog size does affect lifespan. But is there anything that pet parents can do to help their dog — no matter their size or breed — to live a longer and happier life? Let's find out!

Why Do Small Dogs Live Longer?

One thing to keep in mind when talking about the average lifespans of small, medium, large and giant breed dogs is that these are average figures. This means that some dogs will live shorter than the average and other dogs will live longer. But if this is the case, why do small dogs live longer than large dogs?

It is believed that large dogs simply age more quickly than small dogs. It's not uncommon for some giant breeds to gain upward of 100 pounds (45.36 kilograms) in a year, whereas some small breeds may only gain 10 pounds (4.54 kilograms). This rapid growth associated with some giant breeds appears to negatively affect their longevity. When looking at the average lifespans of dogs based on breed, there are often certain generalizations; however, even within the same size category, some dogs may live longer than others due to common health issues associated with a specific breed.

What Is the Average Lifespan of a Dog?

The average lifespan of a dog is dependent on whether they're a small, medium, large or giant dog breed — so the answer varies.

Small Breed Dogs

Smaller breeds, like the Chihuahua and Maltese, which are popular due to their portability, are considered on average to be less than 20 pounds (9.07 kilograms) and have an average life expectancy of 10 to 15 years. However, the oldest known Chihuahua on record, named Megabyte, passed away at 20 years and 265 days old.

Medium and Large Dog Breeds

Medium dog breeds, like many of the spaniel breeds, are approximately 20-50 pounds (9.07-22.68 kilograms) and large breeds, like the popular Labrador retriever and boxer, are usually considered on average to be greater than 50 pounds (22.68 kilograms). The average lifespan for medium and large breeds is approximately 10-13 years.

Giant Dog Breeds

Giant dog breeds are usually considered to be greater than 90 pounds (40.82 kilograms). The average lifespan for a giant breed, such as the regal Great Dane, is unfortunately only 6-8 years, but some have lived to be 11-12 years old or older.

Further, mixed-breed dogs tend to live about 1.2 years longer on average than same-sized purebred dogs.

The current record for the longest-living dog based on Guinness World Records is held by a medium breed dog born in Australia in 1910, an Australian cattle dog named Bluey, who lived for 29 years and 5 months.