It was once thought that one dog year is equal to seven human years, but this is not true!
Different dogs age at different rates. It isn’t quite as simple as saying that for each year that a dog ages, they age the equivalent of seven human years.
Generally the bigger the breed, the quicker they age and the shorter their lifespan.
So how does converting dog years to human years work?
Keep reading to find out just how many human years are equal to one dog year. We also share how to work out your dog’s human age.
Dog Age Calculator
Converting dog years to human years isn’t as simple as multiplying by 7.
There is a much more complicated equation to calculate how old your dog is in human years.
Use our handy human years to dog years calculator below to work it out without having to do any of the maths yourself!
Simply select their current age (in human years) and then select their gender and size.
Dog Age Chart
Many people want to know how old their dog is in human years.
The good news is that until around three years old, most dogs age at the same rate. At three years old most dogs are around 28 human years.
After this age, larger dogs start aging more quickly than smaller dogs.
A good rule of thumb is that the smaller the breed, the longer their average lifespan. A 10 year old Bull Mastiff is the equivalent of 71 in human years, but a 10 year old Jack Russel Terrier is just 56 in human years!
Take a look at our chart below to work out how old is your dog.
|Small (<20lbs)||Medium (21-50lbs)||Large (50-100lbs)||Giant (>100bs)|
|Age of Dog||Age in human years|
How Do Dog Years Work?
Dogs have a much shorter lifespan than humans.
Each year of a dog’s life is equivalent to more than just one human year.
One dog year can be the equivalent of 4 to 16 human years depending on their size, breed, gender and health.
The easiest way to compare the ages of dogs is to look at which stage of life they are in.
A dog’s life is split up into six different stages based on their physical and mental characteristics. Each dog breed will spend a different period of time in each stage of life, and therefore has a different lifespan.
These six life stages are:
- Neonatal (< 2 weeks)
- Puppy (< 6 months)
- Junior (6-12 months)
- Adult (12+ months)
This is when your dog is a newborn puppy and includes the first 2 weeks of their life, no matter the breed or size of the dog.
This is the period where your puppy comes home and is learning and growing. Dogs are considered puppies until they are around 6 months of age.
This is equivalent to your dog being a ‘teenager’. This stage lasts for 6-12 months, until they are finished growing. Larger breeds will be considered junior for longer as they continue growing for much longer than smaller breeds.
Once your dog has finished growing, they are officially adults. For small breeds this will be from 9-12 months, but large breeds will keep growing until they are as much as 2 years old.
Dogs tend to relax and want a quieter life as they hit middle age. This can vary from dog to dog but is usually around 4-5 years for larger breeds and 6-7 for smaller breeds.
As your dog ages they will become slower and show physical signs of aging like greying hair, reluctance to exercise as much and weight gain.
Smaller breeds won’t hit their senior years until they are more than 10 years old.
Larger breeds will be considered senior from as young as 6 years old.
There is a general trend that the larger the breed, the less time they spend in the ‘mature’ and ‘senior’ life stages. This is true even though it takes them longer to grow and become adults.
Dog Years To Human Years
1 dog year to 7 human years doesn’t work as a conversion rate.
So, how does converting dog years to human years actually work?
The answer is that it depends on what size category your dog falls into.
Dog breeds are divided up into 4 main size categories according to their weight when fully grown:
- Small – 0-20 lbs. (e.g. Dachshunds, Pugs and Shih Tzus)
- Medium – 21-50 lbs. (e.g. Cocker Spaniels, Australia Cattle Dogs and Basset Hounds)
- Large – 51-100 lbs. (e.g. Labrador Retrievers, German Shepherds and Boxers)
- Giant: 100+ lbs (e.g. Bull Mastiffs, Great Danes and Rottweilers)
The general rule for conversion is that the smaller the breed, the longer their lifespan.
For a smaller dog, one year can be the equivalent of around 4 human years. For a giant breed, one year can be the equivalent of around 6-8 human years.
This difference is obvious when you compare one of the smallest breeds, to one of the largest.
Chihuahuas have an average life expectancy of 14-16 years, while a Great Dane’s average life expectancy is just 7-10 years. Medium sized dogs like Pitbulls will live for 8-16 years.
This has long confused scientists, because there is a general rule that the smaller the mammal, the shorter their lives. This is the reason why an elephant lives much longer than a mouse, and why a horse lives longer than a hamster!
So why do dogs break this rule?
There are currently three working theories.
The first theory is that bigger dogs age faster. This means you will see signs of old age in bigger dogs from a much younger age than you will in smaller breeds. These signs can include:
- Greying around the muzzle
- Arthritis and joint pain
- Having less energy
- Putting on weight more easily
The second theory is that bigger dogs start aging earlier in life.
Lowering levels of IGF-1 has been shown to slow the rate of aging and extend an animal’s lifespan.
The final theory is that larger dogs have a higher risk of death throughout life, not just later on in life. The main explanation for this is that when the lifespan of dogs of different sizes was investigated, ‘accident’ as cause of death was not excluded.
The research paper did later adjust for accidents, but it still showed that larger breeds aged faster.
Is 1 Dog Year 7 Human Years?
Since the 1950s there has been a long-standing myth that for each year of a dog’s life, they age by exactly 7 human years.
This would mean that:
- 1 year old dog is 7 human years old
- At 2 they are 14 human years
- and so on…
It is thought that this rule was first established because dogs would live approximately 10 years, and humans 70.
To begin with this was a good rule of thumb for a quick calculation from human years to dog years. However, it is now understood that there is a lot more to it than this straight forward conversion of dog years to human years!
A study done by the Department of Medicine at University of California in 2019 showed that dog years to human years do not work that like.
They showed that there is a non-linear relationship between dog and human years.
In more straightforward terms, it is not as simple as 1 dog year equaling 7 human years.
The research showed that dogs reach adulthood much quicker than humans do, but then their aging slows down during adulthood. Dogs only reach their senior years in the last quarter of their lifetime.
All dogs reach their ‘teenage’ years by one year old.
In other words, all dogs are roughly 15 human years old on their first birthday.
Following this, most dogs will reach the ‘mature’ life stage by 5-6 years of age. This stage is the equivalent of a human’s ‘middle age’, making most dogs somewhere in their 40s in human years by the time they are 6 years old.
After this age, dogs of different sizes start aging differently, with large breeds aging much quicker than smaller ones.
A Chihuahua might not be considered ‘senior’ until they reach 10. A giant breed, like a Great Dane, is called ‘senior’ from as young as 6 years old.
How Old Is My Dog?
The best way to estimate a dog’s age is by looking at their teeth.
By 8 weeks old, a puppy will have all their baby teeth. These teeth are very sharp and often compared to sharks’ teeth because of how pointy they are! Your puppy will have all of these teeth when you bring them home.
Puppy teeth will gradually be replaced by permanent adult teeth and will be completely replaced by the age of 7-8 months.
Permanent teeth are bigger and less pointed.
Adult teeth are bright white and completely clean from 9 months to the age of 2.
Over time adult teeth will start yellowing and brown tartar will build up on the surface. This will be obvious from around 3-5 years of age. By 7+ years old there will be signs of wear and tear to the teeth, which look like missing or loose teeth, heavy tartar and worn-down teeth.
Teeth aren’t the only way to age a dog, but it is the most reliable method.
There aren’t many other signs of age, especially in younger dogs.
Signs of aging in senior dogs includes the development of cloudy eyes and gray hair around their muzzle, paws, and stomach.
Cloudy eyes (lenticular sclerosis) do not affect your dog’s vision, but they are associated with old age. Cloudy eyes are usually a sign of a dog being over 7 years old.
Another sign of old age in dogs is gray hair developing around their muzzle, paws, and stomach. This is especially obvious in dogs as they become older than around 8 years of age.
As dogs grow older than 9, they may also experience stiffness and arthritis in their limbs. You may notice they have difficulty jumping or standing up, more so after they have been laying still for a long period of time.
|Puppy teeth||8 weeks to 6 months|
|Bright white and completely clean adult teeth||9 months to 2 years|
|Yellowing and brown tartar on adult teeth||3 to 5 years|
|Missing or loose teeth, heavy tartar or worn-down teeth||7+ years old|
|Cloudy eyes (lenticular sclerosis)||7+ years old|
|Gray hair developing around their muzzle, paws, and stomach||8+ years old|
|Stiffness and arthritis in their limbs||7+ years old|
Things You Can Do To Help Your Dog Live Longer
There are some factors we can control to help our dogs live longer and healthier lives:
- Monitor their daily food intake and feed a balanced diet.
- Regular exercise.
- Keeping on top of vaccines and preventatives.
- Taking your dog for an annual health check.
Approximately 25-30% of dogs in the US are considered obese. Obesity can reduce a dogs lifespan by 1-2 years, so keeping your dog at the right weight is one of the easiest ways to help them live longer.
Being obese not only decreases your dog’s lifespan, but also makes them unhealthier and uncomfortable.
Keep their weight under control by monitoring their daily food intake and making sure they only get the right amount of food for their weight and activity level.
Exercise is another way to control your dog’s weight and keep them healthy.
Although you can’t control everything in your dog’s life, keeping them a healthy weight by feeding a balanced diet and getting regular exercise will help to extend their lifespan.
Keeping on top of parasite prevention and attending regular vet health checks are also helpful.
Making sure your dog is kept up to date on both their vaccines and preventatives is an easy way to keep them safe from diseases.
This comes hand in hand with taking your dog to the vets at least once a year for a complete health check. Vets can pick up on things you might not have otherwise been aware of. They can perform health checks on any lumps, bumps, and scrapes, as well as checking in their mouth, ears, and eyes.
- 1 dog year is not equal to 7 human years. This once common belief, has recently been debunked as there is a non-linear relationship between dog and human years.
- One dog year can be the equivalent of 4 to 16 human years depending on the dog’s size, breed, gender and health.
- All dogs are roughly 15 human years old on their first birthday.
- After three years of age different size dogs start aging at different speeds.
- Big dogs age faster and reach old age earlier than smaller ones.
- The smaller the dog breed, the longer their lifespan. Small breeds like Dachshunds tend to live up to 15 years, whereas giant breeds like Bull Mastiffs only live on average 6-7 years.
- The easiest way to age a dog is by looking at their teeth, but you can also tell a senior dog by looking for gray fur, cloudy eyes, and stiff limbs.
- To help our dogs live healthier for longer we can make sure they maintain a healthy weight, get enough exercise, stay up to date on vaccines and parasite control and receive regular health checks.