In the common misconception of how we calculate dog years every year of your dog’s life is worth seven in human terms. But is this an accurate way of assessing the relative age of your dog? According to the latest research, it is way off, with the real formula being much more complicated. 

Whilst A&T Dogs provide dog training and doggy day-care service, the team is becoming more aware of the correlation between the dog’s age groups and their characteristics. We can then maximise our tailored approach to daycare schedules and activities or training regimes to suit what works for different ages. 

Where Did ‘Dog Years’ Come From?

Some dogs have been known to live longer into their late teens, making them well over a hundred. What’s more, larger dogs are known to have a shorter lifespan than smaller dogs, further undermining the ‘dog years’ formula. 

Non-Linear Development In Dogs

Anyone who has dogs, or who works with them in dog kennels or doggy day-care, knows that dog development is not a straight line. Dogs mature fast from birth, developing teeth within eight weeks and reaching sexual maturity by around nine months. In humans, teeth don’t appear until around nine months and sexual maturity happens around age 12. Clearly, dogs mature rapidly at first, then slow down as they get older.

Calculating Dog Years 

Bearing in mind the non-linear ageing, the American Veterinary Medical Association (AVMA) says that we should consider the first year of a dog’s life to be the equivalent of around 15 human years, the second year to be the equivalent of nine years and every year after that to be worth between four and five human years. 

How Do I Calculate Dog Years in Human Years? 

The formula for dog years comes from dividing the average lifespan of a human, around 77 years, by the average lifespan of a dog, around 11 years. Just reading that you can see that it is not going to be true.

This fits with the ‘dog years’ theory when you consider a seven-year-old dog is 49 human years (7×7) under the ‘dog years’ approach and also 49 under AVMA formula (15+9+(5×5)), however, the important difference is the rate at which they get to this ‘age’.

How Vets Count Dog Years

Generally speaking, vets don’t tend to use an exact formula, preferring to put dogs into ‘life stages’ as follows, based on a life expectancy of 13 years:

  • Puppy Stage – 0 to 9 months – birth to sexual maturity
  • Adolescent Stage – 9 – 12 months – sexually mature and still growing
  • Adult Dog – 12 months to 6 years – finished growing, fully mature
  • Middle Aged Dog – 6½ – 9½years – mid to late maturity
  • Senior Dog – over 9½years – last quarter of average life
  • Geriatric Dog – over 13 years – older than average life

An Alternative Formula To Calculating Dog Years

A study of 104 Labrador retrievers by the University of California, San Diego looked at genetic markers on the DNA called methylation markers, which correspond to ageing in both humans and dogs. They found that a dog‘s age could be calculated using the following logarithmic formula:

Dog’s age in human years = 16 x ln(dog’s age) + 31 years

This puts our seven-year-old dog at around 62 human years. This formula may be more accurate and based on genetic science, but for those of us who can’t do logarithmic functions in our heads, it’s probably easier to use the AVMA system of 15 + 9 + 5 + 5… etc.

Do Different Dog Breeds Age At Different Rates?

Even the simplified approach above has its problems, as different breeds age at different rates. Unlike most other animals, where larger creatures tend to live longer than smaller ones (think elephants vs mice), larger dogs have a shorter life expectancy than smaller ones. Research from Gottingen University in Germany found that every 4.4 pounds (2 kg) increase in body mass reduces a breed’s average life expectancy by around a month. 

 Do Smaller Dogs Live Longer Than Larger Dogs? 

Larger dogs tend to age faster and have shorter lifespans than smaller dogs. Smaller dogs and dog breeds typically weigh less than larger ones. Sometimes, this can be a factor in determining your dog’s age and lifespan as larger dogs have a higher physical strain, which results in them ageing more quickly. Furthermore, faster growth can lead to rapid cell growth creating a higher chance of abnormal cell growth also, larger breeds age quicker, so they are susceptible to illnesses sooner. 

Why Do Dog Ages Matter?

Understanding how old your dog really is in human terms is not only fun, it’s important for their health and wellbeing. If you use the traditional ‘dog years’ formula, you can badly underestimate how old your dog really is, and not look after them appropriately or get them the right veterinary care.

When your pet comes to our Lancaster facilities at A&T Trained Dogs, our expert doggy day-care team will accurately assess how old your dog really is, including size and breed factors to design care and activities that are appropriate for them and their life stage. For more information, please contact us online or call us on 01524 587315.