Dog Age Chart: Dog Years to Human Years by Size & Breed

The dog age chart — 1 to 15 years, by size

The table below gives the human-years age for every dog age from 1 to 15, for small dogs (under 20 lb), medium dogs (21–50 lb), and large dogs (51–90 lb). The first two rows are the same for every size — 15 at year 1, 24 at year 2 — and the columns split after that: small dogs add 4 a year, medium dogs add 5, and large dogs add 6. By age 15 the gap between sizes is 26 human years: a 15-year-old small dog is 76, a medium dog is 89, and a large dog is 102.

Dog age in human years — printable reference

Why the first two years count for so much

A 1-year-old dog is not 7 human years old — it is 15. A dog reaches sexual maturity and near-adult size in its first year, which no 7-year-old human does, and by its second birthday it is roughly 24 — a young adult. That is why the AVMA guideline front-loads the first two years: 15 for year 1, 9 more for year 2, and only then a steady 4, 5, or 6 a year. The old times-seven rule gets the shape of ageing backwards: it says a 1-year-old dog is 7 (too young) and a 10-year-old medium dog is 70 (too old — the chart says 64). Use the first-two-years weighting and the numbers line up with how dogs actually develop.

Why size takes over after year 2

After the fast first two years, the columns split because bigger dogs age faster. A small dog adds 4 human years a year, a medium dog 5, and a large dog 6 — and over a decade that compounds: at age 10 a small dog is 56, a medium dog is 64, and a large dog is 72. The gap is the reason large dogs become seniors first: a large dog is a senior at 6, a medium dog at 8, and a small dog at 10. It is the opposite of most animals, where bigger means longer-lived — with dogs, the big breeds wear out sooner, which is why a 7-year-old Great Dane is an old dog and a 7-year-old Chihuahua is barely middle-aged.

Life stages, by size

Puppy: under 1 year — below this chart's range, and the fastest ageing of all: a puppy goes from birth to roughly 15 human years in its first year. Adult: from age 1 until the senior line — small dogs stay adult until 10, medium dogs until 8, and large dogs until 6. Senior: small dogs from 10, medium dogs from 8, large dogs from 6. The senior line is the one that matters for vet care: twice-yearly check-ups, senior blood work, and joint and weight checks start at the senior age for the dog's size, not at a fixed birthday.

Every branch, checked

1 year old: 15 human years, every size — the first year is the same for all dogs.

2 years old: 24 human years, every size — 15 plus 9.

10 years old, Small: 24 plus 8 years at 4 a year is 24 + 32 = 56.

10 years old, Large: 24 plus 8 years at 6 a year is 24 + 48 = 72.

15 years old, Medium: 24 plus 13 years at 5 a year is 24 + 65 = 89.

7 years old, Large: 24 plus 5 years at 6 a year is 24 + 30 = 54 — and already a senior, since large dogs turn senior at 6.

Output · formula · meaning

Who uses this

• The new puppy owner: brings home a 1-year-old dog and learns it is already 15 human years — a teenager, not a child — and that the second year adds 9 more, to 24.
• The medium-dog owner: has a 5-year-old medium dog and learns it is 39 human years — an adult, and 4 more than the old times-seven rule says.
• The large-breed owner: has a 7-year-old large dog and learns it is 54 human years — and already a senior, because large dogs turn senior at 6.
• The senior-dog owner: has a 10-year-old small dog and learns it is 56 human years and just turned senior — the age when twice-yearly vet checks start.

Accuracy & limitations

This chart follows the AVMA guideline — year 1 is 15 human years, year 2 adds 9, then small dogs add 4 a year, medium dogs 5, and large dogs 6 — and the numbers are the guideline's rounded values, not measurements of any one dog. Breeds vary inside every size band: a 50 lb Border Collie and a 50 lb Bulldog do not age identically, and giant breeds over 90 lb (Great Danes, Mastiffs) age faster still — the AVMA and AKC charts treat them separately, and this chart stops at large (51–90 lb). Published charts also differ slightly from each other: the American Kennel Club's year-by-year chart puts a 10-year-old large dog at 66 rather than 72, and a 15-year-old medium dog at 83 rather than 89, because it uses table values that do not rise by a constant amount every year. The difference is the approximation, not an error in either chart — both agree on the shape (fast first two years, bigger dogs faster after) and differ by a few human years at some ages. A newer DNA-based formula (human age = 16 × ln(dog age) + 31) gives yet another set of numbers. Treat every figure here as an estimate for care and feeding decisions, not a veterinary diagnosis — ask your vet about your own dog's age-related care.