Small vs Medium vs Large vs Giant Dogs

How we group sizes

We place each breed in one of four size classes based on typical adult size and lifespan. The boundaries aren't absolute, and breeds that fall between two classes are placed in whichever best matches how the breed usually ages.

• Small: for example Chihuahua, Yorkshire Terrier, Dachshund and Cavalier King Charles Spaniel.
• Medium: for example Beagle, Poodle (Standard), Australian Shepherd and Bulldog.
• Large: for example Labrador Retriever, German Shepherd, Rottweiler and Doberman Pinscher.
• Giant: for example Great Dane, Mastiff, Newfoundland and Cane Corso.

Human years by size

Every dog is counted as roughly 15 human years at age one and 24 at age two, in line with veterinary guidance. From year three we use our own size-adjusted model, and the gap widens with each year:

Lifespan and senior age

Many small breeds live 13–16 years or more, while several giant breeds have a life expectancy of around 8–10 years. This is reflected in when dogs are considered seniors: around 10 for small, 8 for medium, 7 for large and 6 for giant dogs.

Differences through life

• Puppyhood: Large and giant breeds grow for longer and may keep growing until 18–24 months. Controlled growth and the right food matter for their joints.
• Adulthood: Small dogs often have a longer adult period before signs of ageing appear.
• Senior years: Large dogs are more prone to joint problems, while small breeds more often have dental issues.
• Check-ups: Because large dogs age faster, it can make sense to start senior check-ups earlier.