Free dog age calculator
Dog Years Calculator
How old is your dog in human years? This dog age calculator uses a vet age chart by size, shows your dog’s life stage and compares the result with the DNA-based formula from UC San Diego.
Age in human years
Enter your dog’s age and size to see its age in human years.
Estimate only. Not veterinary advice. Every dog ages in its own way, and breed, health and weight matter as much as size. Ask your vet about your dog’s health and care.
Age in human years
–human years
From the size-based vet age chart, rounded to whole years.
Estimate only. Not veterinary advice. Every dog ages in its own way, and breed, health and weight matter as much as size. Ask your vet about your dog’s health and care.
How to use the dog years calculator
- Enter the ageYears plus months, from the birthday or adoption papers. A guess from your vet is fine too.
- Pick the sizeChoose your dog’s adult weight: small, medium, large or giant. For a mixed breed, go by its weight today.
- Read the resultHuman years from the vet chart, the life stage, and the DNA formula as a second opinion. Results update as you type.
Got a puppy that is still growing? The puppy weight calculator estimates how big it will get, and the puppy growth chart shows growth by age and size.
Dog age chart: dog years to human years by size
| Dog’s age | Small up to 20 lb up to 9 kg | Medium 21–50 lb 9.5–22.7 kg | Large 51–90 lb 23–41 kg | Giant over 90 lb over 41 kg | DNA formula (any size) |
|---|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 | 31 |
| 2 years | 24 | 24 | 24 | 24 | 42 |
| 3 years | 28 | 28 | 30 | 32 | 49 |
| 4 years | 32 | 33 | 35 | 37 | 53 |
| 5 years | 36 | 37 | 40 | 42 | 57 |
| 6 years | 40 | 42 | 45 | 49 | 60 |
| 7 years | 44 | 47 | 50 | 56 | 62 |
| 8 years | 48 | 51 | 55 | 64 | 64 |
| 9 years | 52 | 56 | 61 | 71 | 66 |
| 10 years | 56 | 60 | 66 | 78 | 68 |
| 11 years | 60 | 65 | 72 | 86 | 69 |
| 12 years | 64 | 69 | 77 | 93 | 71 |
| 13 years | 68 | 74 | 82 | 101 | 72 |
| 14 years | 72 | 78 | 88 | 108 | 73 |
| 15 years | 76 | 83 | 93 | 115 | 74 |
| 16 years | 80 | 87 | 99 | 123 | 75 |
| 17 years | 84 | 92 | 104 | – | 76 |
| 18 years | 88 | 96 | 109 | – | 77 |
| 19 years | 92 | 101 | 115 | – | 78 |
| 20 years | 96 | 105 | 120 | – | 79 |
adult senior geriatric (at or past typical life expectancy) – not in the chart (very few giant dogs reach this age)
Size columns: the dog and cat age chart published on the American Animal Hospital Association (AAHA) website (Zoetis, 2019), adapted from the Dog Owner’s Home Veterinary Handbook. The chart uses the same weight groups as this calculator. Last column: 16 × ln(age) + 31, rounded.
How dog years are calculated
The old rule of “one dog year equals seven human years” is a myth. Dogs grow up very fast: by their first birthday most dogs are about as mature as a 15-year-old person, and by two they are roughly like a person in their mid-twenties. The AVMA sums it up for a medium-sized dog as 15 human years for the first year, about 9 for the second, and about 5 for each year after that.
After the second birthday, size starts to matter. In the vet chart above, a small dog adds about 4 human years per year, a medium dog 4 to 5, a large dog 5 to 6 and a giant dog 5 to 8. That is why a 10-year-old Chihuahua is about 56 in human years while a 10-year-old Great Dane is about 78.
The calculator reads your dog’s value from the chart. Between birthdays it moves in a straight line from one year to the next. The chart starts at 1 year, so for puppies under one it draws a straight line from birth up to 15, which is only a rough guide.
The DNA formula from UC San Diego (2020)
Human age = 16 × ln(dog age in years) + 31
Researchers at the University of California San Diego studied methylation, chemical marks that build up on DNA with age, in 104 Labrador Retrievers aged 4 weeks to 16 years and compared them with people. The result, published in Cell Systems in 2020, is the formula above. Examples: 1 year ≈ 31, 2 years ≈ 42, 5 years ≈ 57, 10 years ≈ 68, 14 years ≈ 73 human years.
It tells a slightly different story from the chart: young dogs come out older (a 1-year-old is about 31) and old dogs come out younger. It is based on a single breed and does not adjust for size, so we show it as a second opinion, not the main result. It is not meaningful for puppies under about 2 months.
Dog life stages by size
| Size | Senior from (AVMA) | Geriatric from (life expectancy) |
|---|---|---|
| Small up to 20 lb / up to 9 kg | 8–11 years | about 13.4 years |
| Medium 21–50 lb / 9.5–22.7 kg | 8–10 years | about 12.7 years |
| Large 51–90 lb / 23–41 kg | 8–9 years | about 11.5 years |
| Giant over 90 lb / over 41 kg | 6–7 years | about 9.5 years |
Puppy: until about 1 year (rapid growth usually ends at about 6–9 months, later in big breeds). Senior: the last 25% of the expected lifespan, at the ages the AVMA gives for each size; the calculator switches at the first age in the range. Geriatric: at or past the typical life expectancy (AAHA). We use life expectancy at birth for purebred dogs from a study of US Banfield vet hospital records (Montoya et al. 2023): about 13.4–13.5 years for toy and small dogs, 12.7 for medium, 11.5 for large and 9.5 for giant dogs. That study grouped dogs by slightly different weights, so the match with our four sizes is approximate.
Dog years FAQ
How old is a 1-year-old dog in human years?
About 15, according to the vet age chart used by this calculator, which gives 15 human years for the first year for every size. The UC San Diego DNA formula says about 31, because by that measure a young dog matures even faster.
Is one dog year really seven human years?
No. Dogs age much faster at the start of life. The American Veterinary Medical Association (AVMA) puts the first year of a medium-sized dog at about 15 human years, the second year at about 9 more, and each year after that at about 5. The old “times seven” rule probably came from comparing average lifespans of about 10 years for dogs and 70 for people.
How do I calculate my dog’s age in human years by hand?
Count 15 for the first year and 24 at two years. After that, add about 4 human years per year for a small dog, 4 to 5 for a medium dog, 5 to 6 for a large dog and 5 to 8 for a giant dog. The dog age chart on this page lists every year from 1 to 20.
Why do big dogs age faster than small dogs?
Large and giant breeds simply live shorter lives, and nobody knows exactly why. In US records from more than 1,000 Banfield vet hospitals, life expectancy at birth was about 13.4 to 13.5 years for toy and small purebred dogs, 12.7 years for medium, 11.5 for large and 9.5 for giant dogs.
When is a dog considered a senior?
The AVMA says a dog becomes a senior in the last 25% of the expected lifespan for its breed. On average that is about 8 to 11 years for small dogs (under 20 lb), 8 to 10 for medium dogs (20 to 50 lb), 8 to 9 for large dogs (50 to 90 lb) and 6 to 7 for giant dogs (over 90 lb). Senior dogs should see a vet at least twice a year.
What is the DNA (epigenetic) dog age formula?
In 2020, researchers at UC San Diego compared chemical marks on the DNA (methylation) of 104 Labrador Retrievers with those of people. Their formula is: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm and the dog’s age is in years. It was built from one breed only, so it does not adjust for size.
Which dog age calculator result should I trust?
Treat both as rough guides, not medical facts. The vet chart allows for size, which matters a lot for older dogs. The DNA formula is based on biology but only on Labradors. Your vet can judge your dog’s real health and what care it needs at its age.
Sources
- American Animal Hospital Association (AAHA) / Zoetis. My pet’s physiological age (dog and cat age chart, 2019). Dog chart adapted from Eldredge D, Giffin J, Carlson L, et al. Dog Owner’s Home Veterinary Handbook, 4th ed. Wiley, 2007, Appendix B.
- American Veterinary Medical Association (AVMA). Caring for senior cats and dogs (senior ages by size).
- American Kennel Club. How to calculate dog years to human years (AVMA guideline: 15, 9, then about 5 per year).
- Wang T, Ma J, Hogan AN, et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems 2020;11(2):176–185.e6.
- UC Davis School of Veterinary Medicine. Calculating your dog’s age (2020).
- Montoya M, Morrison JA, Arrignon F, et al. Life expectancy tables for dogs and cats derived from clinical data. Frontiers in Veterinary Science 2023;10:1082102.
- AAHA. Canine Life Stage Guidelines (2012; defines “geriatric”) and 2019 Canine Life Stage Guidelines (puppy and senior stages).
Puppy weight calculator
How big will your puppy get? Adult weight range, how grown it is now and a growth chart.
Puppy growth chart
Percent of adult weight by age for toy, small, medium, large and giant dogs.