Calculators
Dog Age Calculator
Enter your dog’s age and size to see its age in human years by two methods side by side, or switch to cat for the feline equivalent and life stage.
36 years
in human years for a medium dog aged 5 years, from the AKC size chart
57 years
DNA methylation formula: 16 × ln(5) + 31 = 56.8
From Wang et al., Cell Systems (2020), fitted on Labrador Retrievers only, and it does not adjust for size or breed.
AKC dog age chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
Human-equivalent years from the American Kennel Club chart “How Old Is My Dog in Human Years?”.
An approximation for fun and orientation, not a health assessment. Processed on your device — nothing is sent anywhere.
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Frequently asked questions
Is one dog year really seven human years?
No. The seven-to-one rule is a popular simplification that does not match how dogs actually age. Dogs mature much faster early on: the AVMA guideline puts the first year of a medium-sized dog at about 15 human years and the second at about 9 more, after which each year counts for roughly 5. Size matters too, because large and giant breeds age faster and have shorter lifespans than small dogs.
Where does the size-based chart come from?
It is the American Kennel Club chart “How Old Is My Dog in Human Years?”, which follows the AVMA guideline and splits dogs into small (20 lb or less), medium (21–50 lb), large (51–100 lb) and giant (over 100 lb). For example, a 10-year-old small dog is listed at 56 human years, a medium dog at 60, a large dog at 66 and a giant dog at 79. The calculator interpolates between whole years.
What is the 16 × ln(age) + 31 formula?
It comes from Wang et al., “Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome”, Cell Systems, 2020 (first released as a preprint in 2019). The researchers compared age-related DNA methylation changes in 104 Labrador Retrievers with those in humans and fitted human age = 16 × ln(dog age) + 31. A 1-year-old dog comes out at 31, a 5-year-old at about 57 and a 12-year-old at about 71.
Which method is more accurate for my dog?
Neither is precise. The epigenetic formula was derived from one breed, Labradors, and does not account for size, so, as the AKC also points out, it may not match dogs of other breeds. The size chart reflects that bigger dogs age faster but is a general guideline, not a measurement. Showing both gives a sensible range; your vet’s assessment of your dog’s health matters more than any conversion.
How do you calculate a cat’s age in human years?
International Cat Care counts the first two years of a cat’s life as about 24 human years, 15 for the first and 9 for the second, and every year after that as 4. A 10-year-old cat is therefore about 56 in human terms. The 2021 AAHA/AAFP Feline Life Stage Guidelines group cats as kitten (up to 1 year), young adult (1–6), mature adult (7–10) and senior (over 10).
Why are dog and cat years only an approximation?
Animals do not age at a fixed ratio to people. Growth, sexual maturity, adulthood and old age arrive at different rates, and in dogs they vary with size and breed. Any conversion compresses those differences into a single number, which is useful for thinking about life stage and care, not for predicting lifespan or health.
About this tool
This dog age calculator converts your dog’s age into human years in two ways and shows them side by side. The first uses the size-based chart published by the American Kennel Club, which follows the American Veterinary Medical Association guideline that a medium-sized dog’s first year is about 15 human years, the second about 9 more, and each later year roughly 5. Because larger dogs age faster, the chart lists giant dogs separately from the first year and separates small, medium and large dogs from age six onward.
The second method is the logarithmic formula from Wang and colleagues’ study in Cell Systems (2020), human age = 16 × ln(dog age) + 31. It was built by comparing DNA methylation, a chemical marker that changes with age, in 104 Labrador Retrievers with the same markers in people. The formula ages dogs quickly at first and then more slowly: 1 year is 31, 2 years is about 42 and 10 years about 68. It was fitted on a single breed and ignores size, and it falls off sharply for very young puppies, so it is not shown under three months.
A cat option applies the International Cat Care table, where the first two years equal about 24 human years and each following year adds 4, and names the life stage from the 2021 AAHA/AAFP Feline Life Stage Guidelines: kitten, young adult, mature adult or senior. Life stages are what vets use to plan checkups, diet and screening, so they are often more useful than the human-years number itself.
“Dog years” are a way to picture where a pet is in its life, not a biological measurement. The old seven-to-one rule does not match how dogs really develop, and even the better methods here are approximations built from averages or from a single breed. Use the result as a conversation starter about your pet’s stage of life, and rely on your veterinarian for anything to do with health. Nothing you enter leaves your browser.