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Dog age calculator

Your dog's age in human terms — using the size-banded table vets actually use, and the 2020 DNA-methylation formula alongside it. The old multiply-by-seven answer is shown too, so you can see how far off it is.

Nothing you enter is sent anywhere. These are estimates, not a veterinary assessment.

In human years — by size

24human years · adult

Epigenetic clock

42

Wang et al. 2020, DNA methylation

Life stage

Adult

Rough guide only

The ×7 rule

14

Shown so you can see how wrong it is

Why the three numbers disagree

The first figure follows the size-banded table vets and the American Kennel Club use, which reflects that a Great Dane ages faster than a terrier. The second comes from a 2020 study that compared DNA methylation in dogs and humans — the only one of the three with a biological basis, but it was derived from Labradors and ignores size entirely. The third is the old multiply-by-seven rule, included because seeing it beside the others is the quickest way to understand that it was never more than a rough guess.

Where multiply-by-seven came from

Nobody is quite sure, and that is the point. The most credible account is that somebody divided a typical human lifespan of around seventy years by a typical dog lifespan of around ten, got seven, and the number stuck because it is easy to do in your head. There is no study behind it.

It fails hardest exactly where people use it most — on puppies. By its arithmetic, a one-year-old dog is seven, which would make it a small child. In reality a one-year-old dog has finished growing, is sexually mature, and is behaviourally something like a teenager. The AKC table puts that dog at fifteen human years. The gap between seven and fifteen is not a rounding difference; it is a different animal.

The size-banded table

Ask a vet and you will usually get a figure from a table banded by adult weight, because size is the single strongest predictor of how fast a dog ages. Small breeds mature quickly in the first two years and then age slowly. Giant breeds keep growing for longer, then age quickly enough that seven is genuinely old for them.

Dog ageSmallMediumLargeGiant
1 year15151512
2 years24242422
5 years36363645
10 years56606679
15 years768393114

Read across a row and the divergence is obvious: at ten, a small dog is in comfortable middle age and a giant breed is well into old age. This is why feeding, exercise and screening advice changes by breed size rather than by age alone.

The epigenetic clock

In 2020 a research group compared DNA methylation — chemical tags that accumulate on the genome in a predictable pattern as an animal ages — in Labrador retrievers and humans, and fitted a curve between them:

human equivalent = 16 × ln(dog age) + 31

Because it is logarithmic, it climbs steeply and then flattens, which matches the shape of how dogs actually mature: an enormous amount of ageing happens in the first year, and far less per year after that. It is the only figure on this page with a measured biological basis. Its limitation is equally clear: it came from one breed, and it says nothing about size, so for a chihuahua or a mastiff it is a rough transfer at best.

What to actually do with the number

The useful output is not the number, it is the life stage it implies. A dog entering the senior band is a dog whose annual check-up becomes twice-yearly, whose diet is worth revisiting, and whose stiffness on the stairs deserves attention rather than a shrug. That judgement does not need the human-year figure to be exact — it needs you to notice the stage changed.

If you know a date of birth and want the exact age first, the age calculator will give it to you in years, months and days.

Is one dog year really seven human years?
No, and it never was. The rule appears to come from dividing a rough 70-year human lifespan by a rough 10-year dog lifespan, which is arithmetic rather than biology. It fails worst at the start of a dog's life: a one-year-old dog is not the equivalent of a seven-year-old child, it is closer to a human in their mid-teens — physically mature, capable of reproducing, and still growing up mentally.
Why do the two figures on this page disagree?
Because they are measuring different things. The size-banded figure follows the table vets and the American Kennel Club use, which reflects the well-documented fact that larger breeds age faster and die younger. The epigenetic figure comes from a 2020 study comparing DNA methylation — chemical marks on the genome that change predictably with age — in dogs and humans. It has a biological basis but was derived from Labrador retrievers and takes no account of size. Neither is wrong; they answer slightly different questions.
What is the epigenetic formula?
Human equivalent age = 16 × ln(dog age in years) + 31, published by Wang and colleagues in 2020. Because it uses a natural logarithm it rises steeply at first and then flattens, which matches how dogs actually mature — most of the ageing happens early. It is not defined for very young puppies, so this calculator leaves it blank below about a month.
Why do big dogs age faster?
This is one of the genuinely open questions in the field. Across species, larger animals usually live longer, but within dogs the relationship reverses: a Great Dane is elderly at seven while a chihuahua of the same age is middle-aged. The leading explanations involve faster growth rates and higher levels of growth factors carrying a cost later in life, but it is not settled, and any calculator that implies certainty here is overselling.
How accurate is any of this?
Treat all of it as an estimate. Breed, weight, neutering, dental care, diet and luck all move the answer, and two dogs of the same age and size can be in very different condition. Use these numbers to understand roughly what life stage your dog is in — which is what actually changes how you feed and exercise them — and use your vet for anything that matters.
What if I do not know my dog's exact date of birth?
Estimate to the nearest few months; at adult ages the difference barely moves the result. If your dog is a rescue, a vet can usually estimate age from teeth, and for a puppy that estimate is quite good. If you do know a date of birth, work out the exact age first with the age calculator and enter that.