How To Tell Your Dog’s TRUE Age | A Guide To Dog Development
Understanding your dog’s age is essential for providing proper care and meeting their evolving needs at different life stages. While we cherish every moment spent with our companions, accurately gauging their age isn’t always straightforward. Whether you’ve adopted a rescue or you’re simply curious about your own dog’s stage in life, decoding your dog’s age requires a bit of detective work.
Here, we’ll delve into the various methods and indicators that can help you determine your dog’s age with reasonable accuracy. From physical cues to behavioral traits, we’ll explore the subtle nuances that mark each developmental stage in your dog’s life, show how to find your dog’s ‘true age’ in human years, and give you a familiar equivalence to help you better understand dog development from playful puppyhood through their golden years.
How To Tell Your Dog’s Age
A dog’s age estimation is most accurate when based on clinical findings. These physical characteristics can vary from dog to dog, but overall they are visible in most dogs of normal health status. While some will allow you to determine an exact age, others will give you range or an indication of ‘no younger than # years old’.
Dentition
Dentition aging is the method of aging based on your dog’s teeth. It’s also the easiest and quickest method with no special equipment required.
Teeth change immensely throughout a dog’s life, especially in the early years. In puppies, eruption of deciduous (milk/baby teeth) and adult teeth can be extremely helpful in estimating age. In addition to the simple absence or presence of these teeth, a more accurate estimate can be attained by measuring the width of the pulp cavity (the chamber containing the crown).
Canine Dentition Formulas:
Number of teeth (upper/lower)
Deciduous = 2*(Incisor 3/3 + Canine 1/1 + Premolar 3/3) = 28
Permanent = 2*(Incisor 3/3 + Canine 1/1 + Premolar 4/4 + Molar 2/3) = 42
| Deciduous teeth (age in weeks) | Permanent teeth (age in weeks) | |
| Incisors | 3-6 | 12-20 |
| Canine | 3-5 | 12-24 |
| Premolars | 4-12 | 16-24 |
| Molars | not applicable | 16-28 |
While much more difficult once the deciduous teeth are gone (usually by 6 months of age), dentition can also be used to help age adult dogs. This is most commonly performed by visually inspecting a dog’s mouth from canine tooth back to molars. Look for tooth staining, tartar buildup, and gum inflammation. The more severe, the older the dog.
This method, though moderately reliable, is not 100% accurate. Factors such as genetics, breed, size, and individual care level can have a large impact on the appearance of a dog’s teeth. If you are unsure, compare your dog’s teeth to another dog who’s age you know.
Bone Development
For dog’s under the age of 2, bone development can be used to accurately estimate age. At specific ages in a young dog’s life, ossification centers (the areas inside the bones in which they solidify) and epiphyseal plates (flat bony structures at either end of long bones that hold growth plate cartilage) slowly change in appearance before closing completely.
These changes are best identified with radiographs (x-rays), and can be confirmed by a veterinary radiologist. Multiple radiographs are best and should be taken 1 month apart to better identify changes in bone development.
Nuclear Sclerosis
Nuclear sclerosis refers to a compression of the central region of the lens in the eye called the nucleus due to a buildup of the fibers of the lens over time that are produced throughout the dog’s life. This can result in cloudiness, hardening, and yellowing of the nucleus of the eye due to its increase in density.
Nuclear Sclerosis can be used to indicate an animal that is over 5 years of age, but is most often noted in dogs 8-10 years of age.
Benign Prostatic Hypertrophy
Benign Prostatic Hypertrophy is an enlargement of the prostate in which small pockets of fluid can form. This condition is exclusively seen in male dogs and is a natural consequence to aging. BPH diagnosis can be used to confirm the age of an intact male dog is over 5 years.
Heart Valve Appearance
The appearance of a dog’s heart on an echocardiogram can suggest an approximate age to a veterinary cardiologist.
Specific structural differences between young and old dogs include left ventricle wall thickness and relative wall thickness. The diastolic wall stress index (WSID) is significantly decreased in old dogs (P<0.05). Young and old dogs show similar electrical and systolic function, but overall, old dogs have a different cardiac structure compared to young dogs.
Additional Assigns of Aging
While not a good metric for determining a dog’s exact age, there are other obvious external signs of aging. Common clinical signs include loss of pigmentation (whitening of fur), decrease in skin and fur condition (dryness & brittleness), diminished senses (hearing & vision impairment), lethargy (reduction in overall activity), and lowered immunocompetence (more susceptible to disease).
There are also several behavioral changes in aging dogs such as increased irritability, nervousness, and restlessness. Although, these symptoms could also signal underlying health conditions so check with your veterinarian. Especially, considering the increased likelihood of these conditions that come with aging.
Dog Age in Human Years
Understanding your dog’s age in human terms can provide valuable insights into their life stage and behavior to help you tailor their care and training accordingly. The adage that one dog year equals seven human years is a well-known approximation, but the reality is far more nuanced. Just like humans, dogs age at different rates depending on various factors such as breed, size, individual experiences, and overall health.
We can play with the numbers, however, to get an idea of your dog’s age in human years in terms of lifespan equivalence. This is mostly based on weight, but a multitude of other factors influence lifespan. After all, not even all humans live to the same age. See the chart below for an estimate on your dog’s age in human years.
| Weight (lbs) | Weight (lbs) | Weight (lbs) | Weight (lbs) | |
| Age (yrs) | 0-20 | 20-50 | 50-90 | >90 |
| 1 | 7 | 7 | 8 | 9 |
| 2 | 13 | 14 | 16 | 18 |
| 3 | 20 | 21 | 24 | 26 |
| 4 | 26 | 27 | 31 | 34 |
| 5 | 33 | 34 | 38 | 41 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 78 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 101 |
| 14 | 72 | 78 | 88 | 108 |
| 15 | 76 | 83 | 93 | 115 |
| 16 | 80 | 87 | 99 | 123 |
| 17 | 84 | 92 | 104 | 131 |
| 18 | 88 | 96 | 109 | 139 |
| 19 | 92 | 101 | 115 | |
| 20 | 96 | 105 | 120 | |
| 21 | 100 | 109 | 126 | |
| 22 | 104 | 113 | 130 | ⃞ Juvenile |
| 23 | 108 | 117 | ⃞ Adult | |
| 24 | 112 | 120 | ⃞ Senior | |
| 25 | 116 | 124 | ⃞ Geriatric |
Developmental Equivalence
While the numbers for dog to equivalent human years are based on a lifespan ratio, the ratio of age to equivalent life stage is not proportional. In other words, a two-year-old great dane is not going to be in the same life stage in terms of development and behavior as an eighteen-year-old teenager. This is especially true in young puppies. Generally speaking, puppies develop at a much faster rate than people. This holds more true the younger the age.
See the chart below for a life stage equivalence breakdown
| Stage | Dog Age | Human Equivalence | Developmental Changes |
| Neonate/Newborn | 0 – 3 weeks | 0 – 3 months | – Just like newborns, neonatal puppies are completely dependent on their mother at this stage -Both babies and puppies will spend almost all of their time sleeping and eating -While babies can hear and see to some degree as newborns, neonates have their eyes and ears completely sealed for the first few weeks |
| Puppy/Infant | 3 – 8 weeks | 3 – 12 months | -This stage is when both infants and puppies will gain a small amount of independence. -Puppies and infants become ambulatory and find their voice during this stage -You’ll notice a change in their behavior as well as they will get more expressive, social, and begin to play |
| Youth/Toddler | 8 – 15 weeks | 1 – 3 years | -This is the roly-poly puppy stage. While still hilariously clumsy, they begin to run and explore the world -This is also when puppies and babies get most of their socialization; learning what’s fun and what’s scary -Most puppies will leave their mother and siblings and go to their new home at this stage |
| Juvenile/Child | 15 weeks – 6 months | 3 – 12 years | -This is the stage puppies and children get settled into their patterns and routines -They will begin to lose their teeth. So chew toys are a must. Just make sure they don’t share too often 😉 -Puppies and babies are still highly social, but for many, stranger danger is beginning to kick in |
| Adolescent/Teenager | 6 months – 1 year | 13 – 18 years | -This is the awkward teenage phase for your dog -Just like with people, dogs grow up first before filling out. This can give your adolescent dog a goofy appearance in this stage -Your puppy will reach sexual maturity at this stage as they settle into full grown adulthood |
| Young Adult | 1 – 3 years | 18 – 25 years | -This is the stage in which your dog will reach full development and enter into the adult phase -Many young adult dogs still act very much like an overgrown puppy, but have the appearance of a full grown dog -In male dogs, this is when testosterone levels are at their peak, as much as 7x their baseline as adults |
| Adult | 4 – 7 years | 26 – 65 years | -By now your dog is fully set into adulthood -Your dog will spend most of their lives in this stage -This is when all your hard work and training in the previous stages pays off |
| Senior | 7 – 11 years | 65 – 80 years | -Your dog has officially entered its senior years -They will start to show the external signs of aging mentioned earlier -Your dog’s activity level will begin to slow down…finally! |
| Geriatric | 11+ years | 80+ years | -These are your dog’s golden years -Most geriatric dogs return to a puppy like role of eating and sleeping all day -Health issues are common and likely at this age -Give your dog the best retirement you can and love them for all the time they have left |
Overall
We love our dog’s no matter what stage of life they’re in. But knowing your dog’s age and understanding how it translates to a familiar frame of reference is key to providing the level of care, training, and attention that your dog needs. Each stage of life in dogs is as different and transformative as they are in people. Learn how to tell your dog’s age, what that age is in human years, and how that stage of life translates to people and you will ensure them a long and happy life with you.
