Dog age calculator
A dog’s first year is about 15 human years and its second adds about 9 more. After that, large dogs age faster than small ones. The old "times seven" rule is a myth.
- Each year now adds
- 6 human years
- Dog’s actual age
- 5.0 years
A medium dog aged 5 years. Bigger dogs age faster once they're grown.
An estimate. Breed, health and lifestyle all affect how fast a dog ages.
Dog years to human years by size
From the Purina UK dog age chart.
| Dog’s age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 12 |
| 2 years | 24 | 24 | 24 | 22 |
| 3 years | 28 | 28 | 28 | 31 |
| 4 years | 32 | 32 | 32 | 38 |
| 5 years | 36 | 36 | 36 | 45 |
| 6 years | 40 | 42 | 45 | 49 |
| 7 years | 44 | 47 | 50 | 56 |
| 8 years | 48 | 51 | 55 | 64 |
| 9 years | 52 | 56 | 61 | 71 |
| 10 years | 56 | 60 | 66 | 79 |
| 11 years | 60 | 65 | 72 | 86 |
| 12 years | 64 | 69 | 77 | 93 |
| 13 years | 68 | 74 | 82 | 100 |
| 14 years | 72 | 78 | 88 | 107 |
| 15 years | 76 | 83 | 93 | 114 |
| 16 years | 80 | 87 | 99 | 121 |
How we calculate this
We use the Purina UK dog age chart, which gives a human-equivalent age for each year of a dog’s life, by size. Between birthdays, we work it out proportionally.
As a rough guide to size by adult weight: small up to 9 kg, medium 10 to 23 kg, large 23 to 41 kg, and giant over 41 kg. For dogs older than 16, we continue at the same rate as the last year in the chart.
Questions people ask
Is one dog year really seven human years?
No. Dogs grow up very quickly, so the first year is worth about 15 human years for most dogs, and a two-year-old is about 24. After that it depends on size, with small dogs adding about 4 years each year and giant breeds about 7.
Why do big dogs age faster?
Larger breeds tend to have shorter lives, so they reach old age sooner. A 10-year-old giant breed is about 79 in human years, compared with 56 for a small dog.
When is a dog a senior?
It varies by size: larger breeds reach their senior years sooner than small ones. Ask your vet when to start senior health checks for your dog.
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