Dog Age Calculator Dog Years to Human Years by Size
Step 1: Enter your dog’s age
Step 2: Pick your dog’s adult size, or type its weight (the answer updates as you go)
| Dog’s age | Small | Medium | Large | Giant |
|---|
Estimate only, not veterinary advice: dogs age at different speeds by breed, health and care. Ask your vet about your own dog. Everything runs in your browser and nothing you type is sent to QuickOnlineTips.
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About this tool
This free dog age calculator turns your dog’s age into human years, adjusted for size, because a Chihuahua and a Great Dane do not age at the same speed. Enter the age in years and months, pick small, medium, large or giant (or type the weight), and see the human-years answer, the life stage and a full dog years chart.
Quick answer: A dog’s first year equals about 15 human years and the second year adds about 9 more, so a 2-year-old dog is roughly 24. After that each dog year adds about 4 human years for small dogs, 5 for medium, 6 for large and 7 for giant breeds. A 5-year-old medium dog is about 39 in human years.
How to calculate dog years to human years
The old “multiply by 7” rule is a myth. Dogs grow up very fast: most reach adulthood within a year or two, then age more slowly. The method used here follows the size-based guideline published by the American Veterinary Medical Association (AVMA) and repeated by the American Kennel Club:
- Year 1: about 15 human years for every dog.
- Year 2: about 9 more, so 24 at age two.
- Every year after: about 4 (small), 5 (medium), 6 (large) or 7 (giant) human years.
So the formula after age 2 is: human years = 24 + (dog age − 2) × the yearly rate for your dog’s size. Puppies under a year are worked out in proportion, so a 6-month-old puppy is about 8 in human years.
Dog years chart by size
| Dog’s age | Small (up to 20 lb) | Medium (21–50 lb) | Large (51–90 lb) | Giant (over 90 lb) |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 5 years | 36 | 39 | 42 | 45 |
| 7 years | 44 | 49 | 54 | 59 |
| 10 years | 56 | 64 | 72 | 80 |
| 12 years | 64 | 74 | 84 | 94 |
| 15 years | 76 | 89 | 102 | 115 |
The calculator above shows the same chart from 6 months to 16 years and highlights your dog’s row and size.
Why big dogs age faster
Large and giant breeds grow for longer as puppies but then age faster as adults, and on average they live shorter lives. Small breeds often live 12 to 16 years, while giant breeds such as Great Danes and Mastiffs usually live 7 to 10. That is why the gap between sizes widens with every year after the second birthday.
The epigenetic estimate
From age 1 the calculator also shows a second figure from a 2020 study by researchers at the University of California San Diego (Wang and colleagues, published in Cell Systems). They compared DNA-ageing marks in Labrador Retrievers and people and proposed: human age = 16 × ln(dog age) + 31. It puts young adult dogs much “older” than the AVMA chart (a 1-year-old is about 31) and older dogs closer together. It was measured in one breed, so treat it as a curiosity and use the size-based answer for everyday care.
When is a dog a senior?
Roughly: small dogs around 10 years, medium dogs around 8, large dogs around 7 and giant breeds as early as 6. Senior dogs benefit from vet check-ups twice a year, as many vets recommend, so changes are caught early.
This is an estimate for fun and general care planning, not veterinary advice. For human ages, try the age calculator, or convert pounds and kilograms with the weight converter.
FAQ
How old is a 1-year-old dog in human years?
About 15. Most dogs are already like teenagers at their first birthday.
Is one dog year really seven human years?
No. The “times seven” rule comes from comparing average lifespans and gets puppies and older dogs wrong. Size-based charts are closer.
Which size is my mixed-breed dog?
Go by your dog’s adult weight: type it in the weight box and the calculator picks the size for you.
Does this work for cats?
No. Cats age differently from dogs and do not vary by size in the same way.
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