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Dog Age Calculator: Dog Years to Human Years
Enter your dog's age and size to see their age in human years. This dog age calculator uses the size-based dog years chart that veterinary sources publish, because a small dog and a giant breed of the same age are not the same age in human terms. It also shows the 2020 epigenetic formula from UC San Diego as a second estimate, and your dog's life stage.
Life stage:
Second estimate (UC San Diego epigenetic formula):
These are estimates for comparison, not a medical assessment. Breed, weight and health all shift the real picture, so ask your veterinarian about your own dog.
How Do I Calculate a Dog's Age in Human Years?
The method the American Kennel Club describes, citing the American Veterinary Medical Association, works in three steps for a medium-sized dog:
- The first year of a dog's life equals about 15 human years.
- The second year adds about 9 more, so a 2-year-old dog is about 24.
- Each year after that adds about 5 human years.
Size changes step three. Small dogs add about 4 human years per year, large dogs about 5 to 6, and giant breeds about 7 to 8 once they are past middle age, which is why giant breeds are seniors years before a small dog is. The calculator above reads from the size-based chart below and fills in the months between birthdays.
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Dog Years Chart: Ages 1 to 20 by Size
| Dog's age | Small (under 20 lb) |
Medium (21 to 50 lb) |
Large (51 to 90 lb) |
Giant (over 90 lb) |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 28 | 30 | 32 |
| 4 | 32 | 33 | 35 | 37 |
| 5 | 36 | 37 | 40 | 42 |
| 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 | - |
| 18 | 88 | 96 | 109 | - |
| 19 | 92 | 101 | 115 | - |
| 20 | 96 | 105 | 120 | - |
Human-equivalent ages in years, from the widely published size-based chart credited to the American Animal Hospital Association. The chart gives no figure for giant breeds past 16, because almost none reach that age; for those ages the calculator continues at the same yearly step and says so.
Why 1 Dog Year Is Not 7 Human Years
The American Veterinary Medical Association says it plainly: dogs do not age at a rate of 7 human years per dog year. Two things break the rule. Dogs mature very fast, then slow down: a 1-year-old dog can already have puppies, which is nothing like a 7-year-old child. And size matters, with small dogs living years longer than giant breeds.
In 2020 researchers at UC San Diego measured this at the level of DNA. Tracking chemical marks on DNA (methylation) in 104 Labrador retrievers across a 16-year age range, they found the relationship is a curve, and proposed the formula human age = 16 x ln(dog age) + 31, where ln is the natural logarithm. By that formula a 1-year-old dog is about 31 and a 7-year-old about 62. The study, Wang et al., Cell Systems 2020, used one breed, so it may not transfer to very small or very large dogs. That is why the calculator shows it as a second estimate beside the size-based chart.
Life Stages: Puppy to Senior
Veterinarians care less about human years than about life stage, because the stage sets the care plan. The 2019 AAHA Canine Life Stage Guidelines define four:
- Puppy - birth until rapid growth stops, around 6 to 9 months.
- Young adult - until physical and social maturity, about 3 to 4 years.
- Mature adult - from maturity until the last 25% of estimated lifespan.
- Senior - the last 25% of estimated lifespan through end of life.
Because lifespan depends on size, the senior line moves. This calculator starts the senior stage at about 11 years for small dogs, 10 for medium, 8 for large and 6 for giant breeds, and labels dogs past the typical lifespan for their size (15, 13, 11 and 9 years) as geriatric. Geriatric is an everyday term for the late senior years; AAHA itself goes from senior to end of life. Our guide to when a dog is a senior works the 25% rule out by breed.
How to Tell a Dog's Age Without Papers
For a rescue or a stray, a vet estimates age from the body. You can look at the same signs:
- Teeth. The full set of adult teeth is in by about 7 months. Clean white teeth suggest a dog around a year old; yellowing and tartar build through the adult years; heavy tartar, worn or missing teeth point to a senior. Dental care changes this a lot.
- Eyes. A bluish haze in the lens, called nuclear sclerosis, is a normal aging change that tends to appear in the senior years. It is different from cataracts, which your vet can tell apart.
- Coat. Grey around the muzzle and eyebrows usually arrives in middle age and spreads, and the coat can thin or coarsen.
- Body and movement. Loss of muscle over the hips and spine, stiffness on rising and slower walks suggest an older dog.
None of these is exact, and a vet exam is the best estimate you will get.
Dog Age Calculator FAQ
How do I calculate a dog's age?
Count 15 human years for the first year, 9 for the second, then add about 4 years per year for a small dog, 5 for a medium dog, 5 to 6 for a large dog and 7 to 8 for an older giant breed. The calculator on this page does it for you, including months.
Is 1 year 7 years in dog years?
No. The American Veterinary Medical Association says dogs do not age 7 human years per year. Dogs age fast early and slower later: a 1-year-old dog is about 15 in human years, a 2-year-old about 24, and after that the rate depends on size.
How old is a 14 year old dog in dog years?
A 14-year-old dog is about 72 in human years if small, 78 if medium, 88 if large and 108 if a giant breed.
How old is a 7 year old dog?
A 7-year-old dog is about 44 in human years if small, 47 if medium, 50 if large and 56 if a giant breed. The UC San Diego epigenetic formula puts a 7-year-old dog at about 62.
At what age is a dog a senior?
Veterinary guidelines define senior as the last 25% of estimated lifespan: roughly 11 years for small dogs, 10 for medium, 8 to 9 for large and 6 to 7 for giant breeds.
Written by Marc Brannigan, Co-Founder and CEO of HempMy Pet. Sources: American Veterinary Medical Association; 2019 AAHA Canine Life Stage Guidelines; American Kennel Club; Wang et al., Cell Systems 2020. This page is general information, not veterinary advice.
