How old is a dog in human years, by size? A toy dog ages more slowly than a giant dog after age 2, adding about 4 human years per year against about 7 for a giant dog — so a 10-year-old toy dog is about 56 in human years, and a 10-year-old giant dog is about 80. This guide is the dog age chart by size: the full table, the model behind it, and what the numbers mean for food, exercise, and vet visits. Every figure is an estimate, not an exact conversion. The dog age calculator works out the figure for your dog's exact age and size.
The short version is: a 1-year-old dog is about 15 in human years, a 2-year-old is about 24, and after that a dog adds about 4 human years per year if it is toy or small, 5 if it is medium, 6 if it is large, and 7 if it is giant. Use the table below for your dog's age and size, or the dog age calculator for the exact figure. The how old is my dog in human years guide gives the same model with worked examples.
Dog age chart by size
The table below gives the human-age equivalents for dogs aged 1 to 15, by size. Find your dog's age in the left column, then read across to its size.
| Dog age | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 | 24 |
| 3 years | 28 | 28 | 29 | 30 | 31 |
| 5 years | 36 | 36 | 39 | 42 | 45 |
| 7 years | 44 | 44 | 49 | 54 | 59 |
| 10 years | 56 | 56 | 64 | 72 | 80 |
| 12 years | 64 | 64 | 74 | 84 | 94 |
| 15 years | 76 | 76 | 89 | 102 | 115 |
Read the table from top to bottom and the pattern is clear: a dog ages fast in its first two years — 15 human years in the first year, and 24 by the end of the second — and then slows down, but a large dog slows down less than a small one. At age 5, a toy dog is about 36 in human years and a giant dog is about 45; at age 10, the gap is 56 against 80; at age 15, it is 76 against 115. The gap grows because the larger dog adds more human years per year after age 2.
The model behind the chart
The model most veterinarians use is the AVMA/AKC size model: the first year of a dog’s life equals about 15 human years, the second year brings the total to about 24 human years, and after that you add about 4 human years per dog year for a toy or small dog, about 5 for a medium dog, about 6 for a large dog, and about 7 for a giant dog.
A second way to estimate a dog’s human age comes from a 2020 epigenetic study by Wang and colleagues at the University of California, San Diego, published in Cell Systems: human age equals 16 times the natural logarithm of the dog’s age, plus 31. For a 5-year-old dog that gives about 57 human years, and for a 10-year-old about 68. The two models agree best in middle age and differ most in very young and very old dogs. Use the stage, not the number, to make decisions about food, exercise, and vet visits.
Life stages for dogs
Dogs move through three broad life stages, and the boundaries depend on size:
Puppy or kitten (birth to about 12–18 months). Growth is rapid, especially in the first year. Feed a puppy or kitten food, feed little and often, and keep exercise gentle while joints are still developing.
Adult (about 18 months to senior age). Growth is finished and weight should be stable. This is the longest stage and the easiest to manage: consistent food, daily exercise suited to the breed, and a vet check once a year.
Senior (from about 10 years for a toy or small dog, 8 to 10 for a medium dog, 7 to 8 for a large dog, and 6 to 7 for a giant dog). The last quarter or so of a typical lifespan. Energy often drops, joints stiffen, and senses dull. Vet checks should move to twice a year, food may need adjusting, and exercise should stay regular but gentler.
Those boundaries are approximate. A dog that is lean, active, and healthy may act like an adult well past its senior boundary, while one with a health problem may need senior care earlier. The when is a dog considered a senior guide gives the thresholds by size.
How to use the chart
Find your dog's age in the left column, then read across to its size. If your dog is between two ages in the table, take the nearer one — the models are estimates, and a year either way does not change the stage of life. If you do not know your dog's size, use its weight: a toy dog is typically 1 to 5 kg, a small dog 5 to 10 kg, a medium dog 10 to 25 kg, a large dog 25 to 40 kg, and a giant dog 40 to 90 kg. The average dog weight by breed size guide gives the full size tables.
Use the chart to plan care, not to worry: a dog that is a puppy or kitten needs puppy or kitten food and gentle exercise, an adult needs measured food and daily exercise, and a senior needs twice-yearly vet checks and gentler exercise. The number in the chart is a guide to the stage, not a prescription — and a dog's weight, health, and activity matter as much as its age. The dog age chart by breed guide gives the figures breed by breed, and the how to calculate dog age guide gives the step-by-step method.
Common mistakes
The most common mistake is the 'multiply by seven' rule: multiplying by seven gives 35 human years for a 5-year-old dog, against about 39 on the size model — and it is wrong in the other direction for puppies and kittens, where a 1-year-old dog is already about 15 in human years, not 7. The second mistake is using the dog model for a cat, or the cat rule for a dog: dogs and cats age differently, and the models are not interchangeable.
The third mistake is taking the number too literally: the models give an estimate of the stage of life, not an exact conversion, and two dogs of the same age can be in very different shape. The fourth is forgetting size for dogs: a large dog ages faster than a small one, so a 10-year-old Great Dane is much older in human years than a 10-year-old Chihuahua. The dog years to human years converter and the cat years to human years converter give the same figures as a converter.
For related reading, see the dog age calculator, the dog age calculator guide, the how old is my dog in human years guide, the dog age chart by breed guide, the when is a dog considered a senior guide, the average dog weight by breed size guide.
Frequently asked questions
How old is a dog in human years by size?
A 1-year-old dog is about 15 in human years, a 2-year-old is about 24, and after that a dog adds about 4 human years per year if it is toy or small, 5 if it is medium, 6 if it is large, and 7 if it is giant. A 10-year-old toy dog is about 56, and a 10-year-old giant dog is about 80. Use the table above for your dog's exact age and size.
Is the 'multiply by 7' rule right?
No. Multiplying by seven gives 35 human years for a 5-year-old dog, against about 39 on the size model — and it is wrong in the other direction for puppies and kittens, where a 1-year-old dog is already about 15 in human years, not 7.
How old is a 10-year-old dog in human years?
A 10-year-old toy or small dog is about 56 in human years, a medium dog about 64, a large dog about 72, and a giant dog about 80.
When is a dog considered a senior?
A dog is usually considered a senior from about 10 years for a toy or small dog, 8 to 10 for a medium dog, 7 to 8 for a large dog, and 6 to 7 for a giant dog. Those are rough guides, and your vet may move the boundary earlier or later depending on your individual dog's health.
How long do dogs live?
Typical lifespans by size are about 12 to 16 years for toy breeds, 12 to 15 for small breeds, 10 to 14 for medium breeds, 10 to 12 for large breeds, and 7 to 10 for giant breeds. Those are ranges, not promises.
How do I work out my dog's size?
Use its weight: a toy dog is typically 1 to 5 kg, a small dog 5 to 10 kg, a medium dog 10 to 25 kg, a large dog 25 to 40 kg, and a giant dog 40 to 90 kg. The average weight by breed size guide gives the full size tables.
Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.