There is no short answer for when a dog is considered a senior. Dogs don’t have just one standard age for seniority because, depending on certain factors, they have different life expectancies.

Smaller dogs often live over 15 years (sometimes longer than 20), medium and large-size dogs typically live between 10-15 years, and some giant dog breeds such as mastiffs, may only live 6  to 10 years. 

Veterinarians consider dogs to be “seniors” when they reach the last 25 percent of the estimated lifespan for their breed.

Different breeds are considered seniors at these age ranges (on average):

  • 8 to 11 years for small breeds
  • 8 to 10 years for medium and large breeds
  • 6 to 7 years for giant breeds.

In this article, we’ll talk about the aging process in dogs and how it compares to human years.

Your Dog’s Age in Human Years

The idea that one dog year is equivalent to seven human years is a concept that has been passed down through many generations. It likely came from the fact that the average lifespan for humans used to be approximately 70 and approximately 10 for dogs, so therefore, a 7 to 1 ratio made sense.

However, this theory doesn’t consider the many other factors that influence the aging process in dogs, such as size, breed, lifestyle, weight, and health – to mention a few. 

There are several new approaches to convert dog years to human years

For instance, The American Veterinary Medical Association (AVMA) provides these guidelines:

  • The first year of a dog’s life is equal to 15 human years
  • The second year of a dog’s life is equal to about 9 human years.
  • Each additional year is equal to about 4 to 5 human years.

There is another methodology developed by researchers from the University of California San Diego, based on changes observed in Human DNA vs Dog DNA over time. This approach might be more precise but is more complex to calculate.

The formula is as follows: Human age = 16*ln(dog age) + 31

Let’s use the formula to calculate my own furry friends' ages:

Example 1: Mickey, a 14-year-old Shih Tzu is about 73 in human years.

16 * ln(14) + 31

16 * 2.6 + 31

42.2 + 31

Mickey's age in human years is 73.2.

Example 2: Boston, a 10-year-old terrier is about 68 in human years.

6 * ln(10) + 31

16 * 2.3 + 31

36.8 + 31

Boston's age in human years is 67.8.

Example 3: Bobo, a 7-year-old Shih Tzu is about 62 in human years.

16 * ln(7) + 31

16 * 1.9 + 31

31.1 + 31

Bobo's age in human years is 62.1.

Mickey, the 14 year old Shih Tzu is about 73 in human years.Boston, a 10-year-old terrier is about 68 in human years.Bobo, a 7-year-old Shih Tzu is about 62 in human years.

Remember, however, that the calculation may not be accurate for every dog because, as mentioned above, breed and size also play a role in the aging rate.

Small, medium, and large breeds tend to age at a similar rate until the age of 5, and after that, the small breed rate remains steady while larger breeds’ aging process speeds up. On the other hand, giant breeds age slower in the first 2 years and then much faster after that. 

If you want to skip the math, here is a conversion chart from dog age to human age.

Dog Years 

Small Breeds

(< 20 lbs)

Medium Breeds

(20-50 lbs)

Large Breeds

(50-90 lbs)

Giant Breeds

(> 90 lbs)
       

Human Years

1

15

15

15

12

2

24

24

24

22

3

28

28

28

31

4

32

32

32

38

5

36

36

36

45

6

40

42

45

49

7

44

47

50

56

8

48

51

55

64

9

52

56

61

71

10

56

60

66

79

11

60

65

72

86

12

64

69

77

93

13

68

74

82

100

14

72

78

88

107

15

76

83

93

114

Signs That Your Dog is a Senior

Some common signs of aging in dogs include:

  • Reduced energy levels, lethargy, and less activity 
  • Difficulty moving
  • Changes in thirst and appetite
  • Weight gain or loss
  • Changes in sleeping patterns 
  • Dental problems that may lead to difficulty in eating 
  • Changes in behavior or temperament, such as disorientation, excessive barking, house soiling, anxiety, etc.
  • Changes in sight or hearing
  • Muscle mass loss, especially in the hind legs
  • White hairs on the face and muzzle

Does My Dog Need an Orthopedic Evaluation?

Let’s Start!
Does My Dog Need an Orthopedic Evaluation?
1. Have you observed that your dog has an abnormal stance or gait?
2. Is your dog limping or favoring their leg or paw?
3. Does your dog have a history of arthritis and seems to be in pain?
4. Is your dog showing signs of lameness (constant or intermittent)?
5. Is your dog showing reluctance or the inability to stand up?
6. Is your dog reluctant or unable to jump up or climb stairs?
7. Is your dog more irritable than usual?
8. Is your dog more lethargic than usual?
9. Does your dog seem to be physically uncomfortable or in pain?
10. Does your dog’s appetite seem less than usual?
11. Has your dog gained weight recently with no explanation?
12. Is your dog more hesitant to go for walks?
13. Is your dog tilting their head more than usual?
14. Is your dog shifting their wait while standing or walking more than usual?
15. Is your dog showing signs of stiffness in legs or joints?
16. Is your dog experiencing swelling of their joints?

Does My Dog Need an Orthopedic Evaluation?

1. Have you observed that your dog has an abnormal stance or gait?
2. Is your dog limping or favoring their leg or paw?
3. Does your dog have a history of arthritis and seems to be in pain?
4. Is your dog showing signs of lameness (constant or intermittent)?
5. Is your dog showing reluctance or the inability to stand up?
6. Is your dog reluctant or unable to jump up or climb stairs?
7. Is your dog more irritable than usual?
8. Is your dog more lethargic than usual?
9. Does your dog seem to be physically uncomfortable or in pain?
10. Does your dog’s appetite seem less than usual?
11. Has your dog gained weight recently with no explanation?
12. Is your dog more hesitant to go for walks?
13. Is your dog tilting their head more than usual?
14. Is your dog shifting their wait while standing or walking more than usual?
15. Is your dog showing signs of stiffness in legs or joints?
16. Is your dog experiencing swelling of their joints?
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Dog Life Expectancy Factors

Besides the factors that we have already mentioned, such as breed, size, lifestyle, etc, there is another variable that contributes not only life expectancy, but also the quality of your pup’s life, and that is weight management. 

Overweight dogs have a significantly lower quality of life than slimmer dogs. That is because obesity can lead to other health problems such as diabetes, joint pain, liver problems, heart disease, skin infections, and the list goes on. That’s why it is so important to give them proper nutrition to promote healthy aging.

Why Do Dogs Age Faster Than Humans?

Sadly our furry friends have a shorter life expectancy than us humans, mostly because their bodies have faster metabolic rates than ours. This means that their bodies will undergo extra labor and will wear out faster. But, with good nutrition and activity, we can help them to live their best lives for as long as possible.

Conclusion

Dogs age at different rates based upon several factors, but there are similarities among breeds of the same size group. So, to answer the question of when a dog enters their golden years, experts have developed guidelines by size:

  • 8 to 11 years for small breeds (less than 20 pounds)
  • 8 to 10 years for medium breeds (20 to 50 pounds)
  • 8 to 9 years for large breeds (50 to 90 pounds)
  • 6 to 7 years for giant breeds (more than 90 pounds)

It is important to be aware of your dog’s aging process and maturity, so that you can monitor their health more closely and take proactive steps to address illness or chronic conditions.