Dog & Cat Age Calculator
Enter your dog or cat's age (and a dog's adult weight) to see how old it is in human years. Dogs are calculated by size.
Dogs use the American Veterinary Medical Association (AVMA) size chart; cats use the International Cat Care / AVMA chart. Breed and health change how fast an individual pet ages.
How to use the dog and cat age calculator
- Choose dog or cat and enter the age in years and months.
- For a dog, enter its adult weight in pounds or kilograms. Weight sets the size class (small, medium, large or giant), because big dogs age faster.
- You get the human-equivalent age, the life stage and how long until the senior years. Add a name to make the result easy to share.
Why "one dog year equals seven human years" is wrong
The seven-to-one rule has no scientific basis. According to the AVMA, a dog reaches the equivalent of a 15-year-old human in its first year and about 24 by age two, then adds roughly 4 to 7 human years each year depending on size. Larger dogs age faster in later life: a 10-year-old small dog is about 56 in human terms, while a giant breed of the same age is about 79.
| Dog age | Small (≤20 lb) | Medium (21–50 lb) | Large (51–90 lb) | Giant (>90 lb) |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
Dogs are generally considered seniors at 8–11 years for small breeds, 8–10 for medium, 8–9 for large and 6–7 for giant breeds (AVMA, citing American Kennel Club data). Twice-yearly veterinary checkups are recommended from then on.
A 2020 study from the University of California San Diego compared DNA methylation in dogs and people and proposed human age = 16 × ln(dog age) + 31. By that formula a one-year-old dog is about 31 and a 12-year-old about 70. The study focused on Labrador retrievers, so the calculator shows it only as a reference value.
Cat age chart
A cat reaches about 15 human years in its first year and 24 by its second birthday, then adds about 4 years for every calendar year. The 2021 AAHA/AAFP Feline Life Stage Guidelines group cats as kittens (under 1), young adults (1–6), mature adults (7–10) and seniors (over 10).
| Cat age | Human age |
|---|---|
| 1 | 15 |
| 2 | 24 |
| 3 | 28 |
| 4 | 32 |
| 5 | 36 |
| 6 | 40 |
| 7 | 44 |
| 8 | 48 |
| 9 | 52 |
| 10 | 56 |
| 11 | 60 |
| 12 | 64 |
| 13 | 68 |
| 14 | 72 |
| 15 | 76 |
| 16 | 80 |
| 18 | 88 |
| 20 | 96 |
Sources: AVMA "Pets Age Faster Than People" and "Senior Pets"; American Kennel Club, How to Calculate Dog Years to Human Years (updated September 2026); Wang T. et al., Cell Systems 2020;11(2):176-185; International Cat Care, How to tell your cat's age in human years (updated November 2025); AAHA/AAFP Feline Life Stage Guidelines (2021). Checked October 18, 2026. Values are averages; individual pets vary by breed and health.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15 human years, and about 24 at age two, according to the AVMA. After that, dogs add roughly 4 to 7 human years each year depending on size.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 60 for a medium dog, 66 for a large dog and 79 for a giant breed.
How do you calculate a cat's age in human years?
A 1-year-old cat is about 15, a 2-year-old about 24, and each year after that adds about 4. A 10-year-old cat is about 56 and a 15-year-old about 76.
Is one dog year really seven human years?
No. Dogs mature much faster than people in the first two years and then age more slowly, and big dogs age faster than small ones, so a single multiplier is wrong at almost every age.
When is a dog considered a senior?
Around 8–11 years for small dogs, 8–10 for medium, 8–9 for large and 6–7 for giant breeds.