Dog years to human years is not a single conversion — it depends on size. A small dog ages slowly, a giant dog ages fast, and a one-size-fits-all chart is wrong for most dogs. This dog years to human years chart gives the full conversion for toy, small, medium, large, and giant dogs from 1 to 15 years, using the AVMA/AKC size model, plus the formula behind it, the UCSD formula as a second opinion, and the life stages each age corresponds to. If you want the answer for one dog, the dog age calculator applies the same model to your dog's age and size in seconds.
The old rule of multiplying by seven is simple but wrong. It says a 1-year-old dog is 7 in human years, when the dog is already about 15 — a teenager, not a small child — and it says a 10-year-old large dog is 70, when the size model says 72 for a large dog but only 56 for a small dog. The seven-times rule is wrong in both directions, and it hides the size difference that matters most. Use the chart below instead.
Dog years to human years chart
Find your dog's age in the left column, then read across to the column for your dog's size: toy (under 5 kg), small (5–10 kg), medium (10–25 kg), large (25–40 kg), or giant (40 kg and over).
| Dog age (years) | Toy / Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 31 |
| 4 | 32 | 34 | 36 | 38 |
| 5 | 36 | 39 | 42 | 45 |
| 6 | 40 | 44 | 48 | 52 |
| 7 | 44 | 49 | 54 | 59 |
| 8 | 48 | 54 | 60 | 66 |
| 9 | 52 | 59 | 66 | 73 |
| 10 | 56 | 64 | 72 | 80 |
| 11 | 60 | 69 | 78 | 87 |
| 12 | 64 | 74 | 84 | 94 |
| 13 | 68 | 79 | 90 | 101 |
| 14 | 72 | 84 | 96 | 108 |
| 15 | 76 | 89 | 102 | 115 |
The chart shows the size gap clearly. At 5 years old, a small dog is about 36 in human years, a medium dog about 39, a large dog about 42, and a giant dog about 45. At 10 years old, the gap is wide: a small dog is about 56, a medium dog about 64, a large dog about 72, and a giant dog about 80. At 12, a small dog is about 64 and a giant dog is about 94. The same birthday means a very different stage of life, and that is why size, not just age, should set your expectations about food, exercise, and vet care.
The formula behind the chart
The AVMA/AKC size model works in three steps. The first year of a dog's life equals about 15 human years. The second year brings the total to about 24 human years. After that, you add about 4 human years per dog year for a small or toy dog, 5 for a medium dog, 6 for a large dog, and 7 for a giant dog. The formula for a dog aged two years or more is therefore human years ≈ 24 + (dog age − 2) × rate, where the rate is 4, 5, 6, or 7 depending on size.
For example, a 7-year-old large dog is about 24 + 5 × 6 = 54 in human years. A 7-year-old small dog is about 24 + 5 × 4 = 44. These are estimates, not exact conversions: individual dogs vary with genetics, diet, health, and care, and the model is a population average. What matters is the stage of life the number points to — puppy, adult, or senior — because the stage, not the number, is what should change food, exercise, and vet visits.
The UCSD formula as a second opinion
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. The researchers compared chemical marks on the DNA of dogs and humans as they age and produced this formula: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm and dog age is in years. For a 5-year-old dog that gives about 57, for a 10-year-old about 68, and for a 15-year-old about 74.
The UCSD formula does not use size, so it gives the same answer for a Chihuahua and a Great Dane of the same age — which is why it is a research model, not a veterinary standard for life-stage decisions. It is most useful as a second opinion: if both models put your dog in the same broad stage of life, you can be confident about the stage, even though the exact number differs. Use the size model in the chart above for practical decisions.
Life stages by age and size
A dog moves through three broad life stages, and the boundaries depend on size. Puppies are dogs up to about 12–18 months, though large and giant breeds keep growing for longer. Adults are dogs from about 18 months until the senior years begin. Seniors are dogs in the last quarter of their expected life: as a rough guide, from about 10 to 12 years for toy and small breeds, 8 to 10 for medium breeds, 7 to 8 for large breeds, and 6 to 7 for giant breeds. Typical lifespans by size are about 12 to 16 years for toy breeds, 12 to 15 for small, 10 to 14 for medium, 10 to 12 for large, and 7 to 10 for giant.
Those boundaries are approximate, and a dog that is lean, active, and healthy may act like an adult well past the senior boundary, while one with a health problem may need senior care earlier. The breed pages on this site give the senior age and lifespan for each breed — for example, the Labrador Retriever age guide and the Great Dane age guide — so you can see the milestones for your own dog rather than a generic average.
How to use the chart
Use the chart to set expectations, not to make medical decisions. If the chart says your dog is a senior, move vet checks to twice a year, review the diet, and keep exercise regular but gentler. If it says your dog is a mature adult, keep weight steady, keep teeth clean, and do not skip the annual vet check. If it says your dog is still a puppy, feed a puppy food, feed little and often, and keep exercise gentle while joints are still developing. And if the chart surprises you — a 1-year-old dog is already 15, a 2-year-old is already 24 — that surprise is the point: dogs live their first two years fast, and the care you give in those years shapes the rest of their life.
For related reading, see the dog age calculator, the dog years to human years converter, the small dog age guide, the Labrador Retriever age guide, the Great Dane age guide, the dog breeds hub.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15 human years on the AVMA/AKC size model, for dogs of all sizes. The first year covers the equivalent of childhood and adolescence, which is why a 1-year-old dog is a young adult, not a puppy any more.
How old is a 10-year-old dog in human years?
It depends on size: about 56 for a small dog, 64 for a medium dog, 72 for a large dog, and 80 for a giant dog. Use the chart above or the dog age calculator.
Why do large dogs age faster than small dogs?
Larger dogs grow faster, age faster, and typically live shorter lives than smaller dogs — a giant breed typically lives 7 to 10 years against 12 to 16 for a toy breed. The reasons are still debated, but the pattern is consistent across breeds.
Is the 'multiply by 7' rule right?
No. It gives 35 human years for a 5-year-old dog, against about 36 to 45 depending on size, and it gives 7 for a 1-year-old, against about 15. Use the size model in the chart above instead.
What is the UCSD dog age formula?
Human age = 16 × ln(dog age) + 31, from a 2020 epigenetic study by Wang and colleagues (Cell Systems). It is a research model, not a veterinary standard, and it does not use size — use the AVMA/AKC size model for practical decisions.
When is a dog considered a senior?
As a rough guide, from about 10 to 12 years for small breeds, 8 to 10 for medium, 7 to 8 for large, and 6 to 7 for giant breeds. Your vet may move the boundary earlier or later for your individual dog.
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.