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Dog Age Calculator by Breed: How Breed Size Changes Dog Years to Human Years

If you have ever wondered why a 10-year-old Great Dane looks old while a 10-year-old Chihuahua still acts young, the answer is breed size. Dogs do not all age at the same speed — and that is why a good dog age calculator asks for breed or size, not just age.

Why breed matters

All dogs age fast in their first two years: about 15 human years in year one, and about 24 by the end of year two. After that, size takes over. Small breeds age slowly (about 4 human years per dog year), medium breeds a little faster (5), large breeds faster still (6), and giant breeds fastest (7). That is the size-based method used in veterinary guidance (AKC, based on AVMA).

So two dogs born on the same day can be very different ages in human years. A 5-year-old Chihuahua is about 36, a 5-year-old Labrador about 42, and a 5-year-old Great Dane about 45. By age 10 the gap is huge: 56, 72 and 80.

Dog age by breed size — examples at age 5 and 10

Size	Example breeds	Age 5	Age 10
Small (under 20 lb)	Chihuahua, Pomeranian, Yorkshire Terrier, Pug	36	56
Medium (21–50 lb)	Beagle, Border Collie, Bulldog, Cocker Spaniel	39	64
Large (51–90 lb)	Labrador, Golden Retriever, German Shepherd, Boxer	42	72
Giant (over 90 lb)	Great Dane, Mastiff, Saint Bernard, Newfoundland	45	80

What if your dog is a mixed breed?

Use adult weight instead of breed. Under 20 lb counts as small, 21–50 lb as medium, 51–90 lb as large, and over 90 lb as giant. Our calculator lets you pick size directly, so mixed-breed owners get an accurate result too.

Popular breeds — age charts

See the full 1–16 year chart for each breed: Labrador Retriever, German Shepherd, Golden Retriever.