The easiest way to determine the average lifespan of a certain dog breed is to look at charts dedicated to this. Another way is to take the size of the breed into account, as it is a well-known fact that smaller breeds live longer. Dogs weighing 20 pounds or less have an average life expectancy of 11 years. Those weighing 90 pounds or more live for around 8 years.
There are some breeds that have especially short life expectancies; one of them is the French Mastiff, expected to live only around 5 to 8 years. The Great Dane and the Bernese Mountain Dog both live for around 6 to 8 years, while the Irish Wolfhound can live up to 10 years. Other breeds with short life expectancies include the Saint Bernard, the Newfoundland and the Scottish Deerhound, with average life spans of 8 to 10 years.
In terms of breeds with long life expectancies, Chihuahuas tend to live for 15 to 20 years. Megabyte is the oldest Chihuahua on record, having died at 20 years and 265 days. In addition, the Australian Cattle Dog is a breed with several records of dogs living over 20 years. Bluey, an Australian Cattle Dog, is the longest living dog on record, having died at 29 years and 5 months.