a five year old medium dog
- Dog age
- 5
- Size
- Medium, 10 to 25 kg
Human equivalent age39
24 at two years, plus three years at five
Open this exampleEverydaypets
Dog and Cat Age Calculator
A dog age conversion that reflects how dogs actually age. The first year is worth about fifteen human years and the second about nine, after which larger breeds age faster than small ones.
Also called: dog years to human years, pet age calculator.
Human equivalent age
39
About 39 in human terms for a medium dog. The old multiply-by-seven rule would say 35, which is wrong at both ends: dogs age fast early and larger breeds age faster throughout.
Under the multiply-by-seven rule
35
Life stage
Adult
Typical lifespan for the size
13
Share of typical lifespan
38.5%
Size category
medium
Method and background
How this is calculated
Multiplying by seven is wrong in both directions. A one year old dog is sexually mature and physically adult, which is nothing like a seven year old child, so the first year counts for around fifteen. The second adds about nine more. After that the rate depends on size: a small dog ages around four human years annually while a giant breed ages six or more, which is why great danes rarely reach ten and terriers often pass fifteen.
dogs mature very fast in the first two years, then age at a rate that depends on their size- y
- Dog age in years
Worked examples
Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
the first year is worth fifteen
- Dog age
- 1
- Size
- Medium, 10 to 25 kg
Human equivalent age15
boundary: where the seven rule is most wrong
Open this examplea giant breed ages faster
- Dog age
- 5
- Size
- Giant, over 45 kg
Human equivalent age43.5
degenerate case
Open this exampleMethod and limits
What it assumes
- Population averages. Individual dogs vary enormously with breed and health.
What it deliberately does not model
- Breed matters as much as size within a category.
- Epigenetic clock research gives a different curve again; this uses the veterinary size-based convention.
Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator
Frequently asked questions
- Why is the seven-year rule wrong?
- Because it is linear and dogs are not. A one year old dog is an adult, and a great dane at eight is far older in body than a chihuahua at eight, which one multiplier cannot capture.