It’s easy to know exactly how old your dog is if you got it from a breeder, but strays and rescues often don’t have a luxury that is a passport. Whether you want to estimate how old your pet is or how are dog years compared to human years developmentally, there are a few handy methods to help you out. Also, are “dog years” even real?

How age of dogs is calculated

First off, let’s start with determining your dog’s actual age. It’s very important information to have because of health reasons – you have to time your vaccinations and medical procedures, also we can’t overestimate how much dog life is impacted by various (dietary, exercise) choices we make depending on its age. Here’s how dog age can be determined reliably.

1. Checking your dog’s teeth

One of the easiest methods and also probably the most accurate one for puppies. 

AgeDescription
1-3 weeksNo teeth
3 weeksFirst canines start appearing
1 monthThe incisors start becoming noticeable
2 monthsFull set of teeth
6 monthsThe first set of teeth starts changing
8-10 monthsPermanent teeth finish forming
1 yearFull fresh set of teeth, white and bumpy
2 yearsThe bumps on the molars are fading away
4 yearsThe teeth lose their gloss and become matte
5 yearsThe tooth enamel starts yellowing
6-7 yearsThe incisors start changing shape, the yellowing continues
8 yearsThe incisors are covered in plaque and become dulled
10 years +Dogs usually start losing teeth, some decay can be noticeable

2. How dog years can be determined by coat

Bad news, they mostly can’t. But the coat does change somewhat during the dog’s life. If you notice grey hair, it means your pet is at least 8-9 years old. Also a good way to tell when a dog is transitioning from puppy to adult – the coat loses some of the silkiness and becomes tougher.

3. How are dog years measured by group

We’ll get to how dog years compare to human years a bit later, but let’s just mention that our pets go through the same developmental stages as people. And determining what group your fluffy friend falls in can be key to finding out how old they are in dog years.

NewbornUp to 2-3 weeks. They mostly sleep and their eyes are closed, no teeth.
Puppy1 month to 1 year. They start learning to walk and interact. By 8-10 months puppies usually get their 1st full set of teeth.
TeenagerIf you were to convert dog years to human, that’s where they start hitting their “teens”. Dogs go through puberty just like any other mammal. Around 12 months of age their body and behaviour starts changing, going through that distinct “awkward” stage.
AdultUsually dogs between 2-7 years of age. Most dogs lose their hyperactivity but become more emotionally stable. The coat and teeth become firmer and tougher.
Senior8 years+. Grey hairs start appearing, the dog moves less and sleeps more. Some health problems can surface so make sure to give your friend lots of attention.

Dog versus human years: the scientific method

People have been trying to find out how many dog years are in a human year since as early as the 13th century – at least that’s where the first written records are from. And while no one exactly knows how the 9 to 1 or 7 to 1 ratios came about, we know that people have been comparing the lifespans of our species since forever. Besides just answering the question of “how old”, dog years in human years should represent the important developmental stages we share.

The Lebeau theory

French scientist A. Lebeau wanted to move away from the simplistic “how many dog years are in one human year” calculation and actually compared the most important development markers in humans and dogs, such as puberty, reaching adulthood and lifespan, giving the phrase “dog years” more meaning. He has discovered that dogs go through as many stages in 1 year as humans do in 15! A 2 year old dog can be compared to a mid-20s human, and then each next year of age 4 “human” years can be added. As you can see, this theory doesn’t give a definite answer about how many dog years in a year that we call “human” – it all depends on the developmental stage.

Your dog goes through as much development as you did in 15 years in just 12 months – that makes your year-old puppy a 9th grader!

Kleiber’s law

Lebeau’s theory, while comprehensive, didn’t take one important thing into account – the impact of dog’s breed, and therefore the size and different physical features. There have been attempts to tie animal lifespan expectations to the famous Kleiber’s Law, dictating that any animal’s metabolic rate scales to the ¾ power of its mass. However, as interesting as it would be to figure out how much dog years is one year of our time just by their weight, this theory didn’t receive any conclusive evidence, because smaller breeds of dogs (especially chihuahuas) despite their fast heart rate and metabolism usually live much longer than the larger breeds. Interestingly enough, Kleiber’s law works on most other animals – so what makes dogs so different? Scientists speculate that the reason may be tied to the growth hormone or to larger breeds being more prone to getting cancer and other life-threatening diseases.

So how are dog years calculated nowadays?

As we mentioned before, people have been trying to convert dog to human years since centuries ago. And 3 main methods persist even up to these days.

  • Using the “7 to 1” rule of thumb, where you just multiply your pet’s “dog years age” by 7 to get their “human years age”. This method is flawed and doesn’t really reflect subtleties, especially in younger animals, but it’s still adopted widely because of its simplicity.
  • Using a rough table, which determines how are dog years compared to human years based on its ballpark size. It obviously doesn’t include all the breeds and you will have to determine which category your fluffy friend falls into by yourself, but overall it’s an easy and visual way to get info and also to compare how dog life cycles differ depending on their size.
  • Using a specialised dog to human years calculator or converter. For your convenience, we have included this calculator right here on this page, just scroll down a little bit. Obviously the most precise method, where all the maths are done by the software, it requires a bit more nuanced input – so obviously you need to know your dog’s exact age before using it. For your convenience, we have combined both the speed and convenience of the “traditional” rule of thumb with the precision that can only be achieved with research.

So how do the methods of how dog years are calculated compare?

MethodPrecision

Measuring

Method

Simplicity
Our dog year converterAs precise as you can get without actual medical testsTakes into account your dog’s breed and precise ageAs simple as pushing a button
The 7 to 1 ruleOff, especially in younger dogsOnly needs a ballpark numberBasic arithmetics

How long do dogs live in general?

Of course when asking the question of how dogs age compared to humans we need to touch on their average life expectancy. The number usually mentioned by the scientists is 12 years – just as the average human is expected to live 70 years, give or take a few, if you remember how dog years are roughly converted to human years, that gives them 12. Of course, it depends greatly on your dog’s breed, genetics, environment, exercise and diet. Smaller dogs are statistically more likely to live longer – some scientists say it’s because the risk of cancer in larger breeds is a staggering 50% to miniature dogs’ 10%. For example, an average bulldog usually lives for just 6 years, while an average border terrier’s life expectancy is a respectable 14. Smaller dogs usually reach adulthood faster, so their biological “clocks” run overtime during the first 2 years of life, but they slow down significantly further down the line. For the big breeds, and especially the giant breeds like mastiffs and great danes, it’s the exact opposite – they develop slower but age almost staggeringly fast.

A dog’s usual life expectancy is around 12 years, which corresponds to a similar span to humans. Smaller dogs are more likely to live a longer life.

Oldest dogs – the record breakers

However, it’s not all doom and gloom when it comes to your favourite pet’s lifespan. If you take into account how dog years are counted, those who get to 20 or more dog years can be considered respectable centenarians. The current benchmark of how old in dog years a pet can live is Bluey, an Australian cattle-dog who lived 29 years and 5 months before passing away in 1939. Bluey is closely followed by Butch the beagle, who lived 28 years, and a welsh collie named Taffy, who brought joy to her family for 27 years and 317 days. In fact, the top list includes a fair bit of collies and dachshunds,so it’s fair to say those breeds are quite robust!

So, does the phrase “dog years” have any meaning?

We have mentioned a few times that the traditional rule of multiplying “dog years” by 7 to get “human years” is little but a myth, but are dog years even real? It’s safe to say they are, since a dog’s time goes by much different from a human’s. They breeze past childhood and adolescence extremely fast, while enjoying their adulthood for a solid several years before slipping into the calm of old age. If you’re curious about how old your pets are in dog years, our handy calculator is right here to do all the work for you. Many factors determine a dog’s developmental stage, with size and breed being the most important, but with the best care provided your pet is sure to live the longest and healthiest possible life.

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