Why do big dogs age faster?

Scientists are not fully sure, but large breeds show age-related changes earlier and have shorter lifespans.

When is a dog a senior?

Around 7 for large and giant breeds, and 10–12 for small breeds.

No, it is a friendly estimate. Genetics, health and lifestyle all matter.

Pick the size category that matches your dog's adult weight.

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Forget "multiply by 7" — enter your dog's age and size for a smarter human-years estimate.

Dog's age

years

Size

In human years that's about

39 years old

Life stage: Adult

Dog age	Small	Medium	Large	Giant
1 yr	15	15	15	15
2 yr	24	24	24	24
4 yr	32	34	36	38
6 yr	40	44	48	52
8 yr	48	54	60	66
10 yr	56	64	72	80
12 yr	64	74	84	94
14 yr	72	84	96	108
16 yr	80	94	108	122

Bigger dogs age faster after their second birthday — regular vet check-ups matter more as they get older.

Dogs grow up fast, then age at different speeds depending on size:

A 6-year-old Labrador (large): 24 + (4 × 6) = 48 human years. A 6-year-old Chihuahua (small) is 24 + (4 × 4) = 40.

Dogs mature much faster in their first two years, and large breeds age faster later on. ×7 gets both wrong.

Enter your dog's weight, age, activity and food calories to see daily calories and cups per meal.

Enter your puppy's age, weight and breed size to see how big they may grow — with a growth chart.

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Last updated September 28, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.