Find your dog’s age in human years. Small, medium, large and giant dogs age at different speeds, so size is part of the calculation.
The old rule that one dog year equals seven human years is easy to remember but not very accurate. Dogs grow up very fast in their first two years, then age more steadily, and big breeds age faster than small ones. This calculator uses size-based charts of the kind vets share, and also shows a newer DNA-based estimate for comparison.
How do I convert dog years to human years?
A dog’s first year is roughly equal to 15 human years, and the second year adds about 9 more, so a 2-year-old dog is about 24. After that, small dogs add around 4 years per year and large dogs 5 to 7. A 5-year-old medium dog is about 42 in human years.
Dog age chart by size
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 5 | 36 | 42 | 45 | 49 |
| 8 | 48 | 56 | 61 | 71 |
| 10 | 56 | 65 | 72 | 86 |
| 12 | 64 | 74 | 82 | 100 |
| 15 | 76 | 87 | 99 | 121 |
The DNA-based formula
A 2020 study of Labrador retrievers compared changes in DNA methylation and proposed this formula. It suggests dogs age very quickly early on. It was based on one breed, so the size charts are still the more practical guide for most owners.
How to use the Dog Age Calculator
Enter your dog's age
Type the age in years. Half years such as 2.5 work too.
Choose the adult size
Pick your dog’s size when fully grown. For mixed breeds, use their current or expected adult weight.
Read the human age
The human-equivalent age appears with the life stage, and the DNA formula and old ×7 rule are shown for comparison.
Frequently asked questions
Is one dog year really seven human years?
No. That rule is a rough average. Dogs mature much faster in their first two years, and large breeds age faster than small ones.
When is a dog considered a senior?
Small dogs around 10 years, medium dogs around 8, large dogs around 7 and giant breeds as early as 5.
Why do big dogs age faster?
Large breeds grow quickly and tend to develop age-related problems sooner, which shortens their average lifespan.
How old is a 1-year-old dog in human years?
About 15 for most dogs, roughly the age of a young teenager.
Can I use this for puppies under one year?
Yes. Enter a decimal such as 0.5 for six months.
Sources and further reading
- How to Calculate Dog Years to Human Years — American Kennel Club
- A Better Method Than "Multiply by 7" — UC San Diego
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Last reviewed: October 2026