Dogs age fast as puppies and then slow down, and big breeds age faster than small ones. This calculator uses breed lifespan data from 584,734 UK dogs and the vets' life-stage guidelines to place your dog on a human timeline.
| Method | Human years |
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No single formula is agreed on, so the tool combines the two things researchers do agree on. Dogs mature very fast in the first two years. After that, how fast a dog ages depends on how long its breed usually lives.
The curve passes through five anchor points. Everything between them is a smooth monotone curve.
Sexual maturity comes at 6 to 9 months in small dogs and 12 to 18 months in giants (AAHA). The senior stage is the last 25% of expected lifespan (AAHA). 80 years is roughly human life expectancy in high-income countries.
McMillan K.M. et al. (2024). Longevity of companion dog breeds: those at risk from early death. Scientific Reports 14, 531. Median lifespans for 155 breeds from 584,734 UK dogs.
Creevy K.E. et al. (2019). AAHA Canine Life Stage Guidelines. JAAHA 55(6). Defines puppy, young adult, mature adult, senior and end of life.
Wang T. et al. (2020). Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems 11(2). Gives human = 16·ln(dog age) + 31, measured in 104 Labrador retrievers only.
Kraus C., Pavard S., Promislow D. (2013). The size–life span trade-off decomposed: why large dogs die young. American Naturalist 181(4). Large dogs age at a faster rate after maturity.
The widely used year-by-year chart by size, popularised by the AVMA: 15 human years for year one, about 9 for year two, then 4 to 7 per year depending on size.
An estimate, not a diagnosis. Individual dogs vary with genetics, weight, neutering and care. The UK data may not match other countries exactly.