Dog Age Calculator
Convert your dog's age to human years by size — or switch to the cat calculator.
21–50 lb (10–23 kg)
A medium dog aged 5 years is about
36human years
- Life stage
- Adult
DNA-based estimate (16 × ln(age) + 31): about 57 years. The old “× 7” rule would say 35.
Dog years to human years chart
| Dog age | Small | Medium | Large | Giant | Cat |
|---|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 | 15 |
| 2 | 24 | 24 | 24 | 22 | 24 |
| 3 | 28 | 28 | 28 | 31 | 28 |
| 4 | 32 | 32 | 32 | 38 | 32 |
| 5 | 36 | 36 | 36 | 45 | 36 |
| 6 | 40 | 42 | 45 | 49 | 40 |
| 7 | 44 | 47 | 50 | 56 | 44 |
| 8 | 48 | 51 | 55 | 64 | 48 |
| 9 | 52 | 56 | 61 | 71 | 52 |
| 10 | 56 | 60 | 66 | 79 | 56 |
| 11 | 60 | 65 | 72 | 86 | 60 |
| 12 | 64 | 69 | 77 | 93 | 64 |
| 13 | 68 | 74 | 82 | 100 | 68 |
| 14 | 72 | 78 | 88 | 107 | 72 |
| 15 | 76 | 83 | 93 | 114 | 76 |
| 16 | 80 | 87 | 99 | 121 | 80 |
Sizes by adult weight: small up to 20 lb (9 kg); medium 21–50 lb (10–23 kg); large 51–90 lb (23–41 kg); giant over 90 lb (41 kg). Estimates only — ask your vet about your own pet's health.
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How to use it
- 1
Pick dog or cat
Dogs use a size-based chart; cats use a single scale.
- 2
Enter the age
Years and months — puppies and kittens work too.
- 3
Choose a size
Larger dogs age faster after about age five.
Frequently asked questions
Is one dog year really seven human years?
No. Dogs mature very quickly — a one-year-old dog is roughly like a 15-year-old human, and a two-year-old like a 24-year-old. After that, each dog year is about 4–7 human years depending on size, with giant breeds ageing fastest.
Why do big dogs age faster?
Large and giant breeds have shorter lifespans and reach senior age sooner (around 6–7 years) than small dogs (around 10 years), so the chart adds more human years per year for bigger dogs.
What is the DNA-based dog age formula?
A 2019 UC San Diego study compared DNA methylation in Labradors and humans and proposed human age ≈ 16 × ln(dog age) + 31. It suggests dogs age very fast early on; it was studied in one breed, so we show it alongside the size-based chart.
How do you convert cat years to human years?
A one-year-old cat is about 15 in human years and a two-year-old about 24. After that, add roughly 4 human years per cat year — so a 10-year-old cat is about 56.