How old is your dog in human years?
Working out your dog's "human age" isn't just fun — it tells you what life stage they're in, which shapes their diet, exercise and vet care. This calculator uses the size-based method vets actually use, so the number reflects how your dog is really aging.
The "1 dog year = 7 human years" myth
The classic rule — multiply your dog's age by 7 — is wrong, and it always was. Dogs don't age at a steady rate. They grow up very fast in the first two years (a 1-year-old dog is already a teenager, not a 7-year-old child), then age more slowly, and the pace depends heavily on their size. The ×7 rule was likely just a marketing line to encourage yearly vet visits.
The real formula, by size
- Year 1 ≈ 15 human years — puppies mature incredibly fast.
- Year 2 adds about 9 more, so a 2-year-old dog ≈ 24 human years.
- Each year after that adds roughly 4 (small) to 7 (giant) human years.
Size is the big variable in later life: small dogs age slowly and often live 14–16 years, while giant breeds age fast and may reach only 7–10. That's why a 10-year-old Chihuahua and a 10-year-old Great Dane are in very different places.
Dog years to human years: every size
Human-equivalent age for dogs of every size, from the same size-based method the calculator uses. Small = up to ~10 kg, Medium = 10–25 kg, Large = 25–45 kg, Giant = 45 kg+.
| Dog age | 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 |
| 16 | 80 | 94 | 108 | 122 |
| 17 | 84 | 99 | 114 | 129 |
| 18 | 88 | 104 | 120 | 136 |
| 19 | 92 | 109 | 126 | 143 |
| 20 | 96 | 114 | 132 | 150 |
How old is a 5 year old dog in human years?
Between 36 and 45, depending on size: 36 for a small dog, 39 for medium, 42 for large and 45 for a giant breed.
How old is a 10 year old dog in human years?
About 56 for a small dog, 64 for medium, 72 for large and 80 for a giant breed — larger dogs age faster after their second year.
How old is my beagle in human years?
Beagles are medium-sized dogs (10–25 kg). A 3-year-old beagle is about 29 in human years, a 7-year-old about 49, and a 12-year-old about 74. See the Medium column above for any age.
Dog life stages
Puppy (0–1 yr): rapid growth, socialisation, lots of sleep. Junior (1–2): full-size but still maturing. Adult (2–7): prime years. Senior (7+ for large dogs, ~10+ for small): watch weight, joints and teeth, and consider twice-yearly vet checks.
A more precise formula (for the curious)
A 2020 study of DNA methylation proposed human age = 16 × ln(dog age) + 31. It maps a 1-year-old dog to about 31 and lines up closely with the size-based numbers for adult dogs — good confirmation that dogs age fast early, then slow down.
Is 1 dog year really 7 human years?
No — that's a myth. Dogs age much faster in their first two years (year 1 ≈ 15 human years) and the rate depends on their size. A single fixed multiplier can't capture that, which is why this calculator uses the size-based method instead.
How do I calculate my dog's age in human years?
Count 15 for the first year, +9 for the second (24 total at age two), then add 4–7 for each additional year depending on size — small dogs add less, giant breeds add more. Enter your dog's age and size above and the calculator does it for you.
Do small dogs live longer than big dogs?
Yes, generally. Small breeds often live 14–16 years while giant breeds may live only 7–10. Larger dogs grow faster and age faster in their later years, which is why size changes the human-age number so much.
When is a dog considered a senior?
It depends on size: giant breeds can be senior by 6, large dogs around 7–8, and small dogs not until 10 or later. Senior dogs benefit from more frequent vet checks and attention to weight and joints.
How can I tell a rescue dog's age?
A vet can estimate age from teeth wear, eye clarity, coat and muscle tone. Once you have an estimate, enter it here to see the human-years equivalent and life stage. Curious about people too? Try the age calculator.