The free guide to life with your dog
Breeds, training, health, food and names
One dog year equals seven human years? It’s a nice round myth, and it’s wrong at both ends. A one-year-old dog is closer to a teenager than a seven-year-old child, and big dogs age much faster than small ones. Here’s a better way to work it out.
Dogs grow up incredibly fast. By their first birthday most are sexually mature and nearly full size, roughly what a 15-year-old human is. By two, they’re young adults, around 24 in human terms. After that, ageing slows down, and the speed depends mostly on size: a Great Dane is a senior at seven, a Jack Russell can still be bouncing at twelve.
A common veterinary rule of thumb: about 15 human years for the first year, 9 more for the second, then 4 to 6 a year depending on size. Figures are rounded.
| Dog’s age | Small dog (under 10 kg) | Medium dog (10 to 25 kg) | Large dog (over 25 kg) |
|---|---|---|---|
| 1 year | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 |
| 5 years | 36 | 39 | 42 |
| 7 years | 44 | 49 | 54 |
| 10 years | 56 | 64 | 72 |
| 12 years | 64 | 74 | 84 |
| 15 years | 76 | 89 | 102 |
In 2020, researchers at the University of California San Diego compared changes in DNA (so-called epigenetic clocks) in Labradors and humans. Their formula: human age = 16 × ln(dog’s age) + 31. It confirms that dogs age very fast early on, then much more slowly. It was built on one breed, though, so use it as a curiosity rather than a rule.
Roughly from seven or eight for big breeds, ten or so for medium dogs, and around twelve for small ones. From then on, a check-up twice a year is a good idea: dental disease, arthritis, kidney problems and lumps are all easier to manage when caught early.
Your vet can estimate age from the teeth (wear, tartar, adult teeth by about seven months), the eyes, the coat and muscle tone. Expect a range of a couple of years rather than an exact figure.
About 15, a teenager, whatever the breed.
Around 56 for a small dog, 64 for a medium one and 72 for a large one.
Generally small breeds and crossbreeds of healthy weight. Giant breeds have the shortest lives.
