Paw Primer
Dog's Age Calculator: Dog Years to Human Years by Size
Enter your dog's age in years and months and its size class; get the human-age equivalent from the AKC size chart and from the 2020 epigenetic-clock formula, side by side.
Dog Age Calculator
Your dog's age in human years by two published methods, shown side by side: the AKC size chart and the 2020 epigenetic-clock formula.
Chart row for a 2-year-old medium dog (21 to 50 lb).
16 × ln(2.00) + 31 = 42.1 human years. Derived from Labrador retrievers; size is not a variable.
Neither number is a veterinary assessment of your dog's health or life stage; both are population-level conversions.
AKC chart: how old is my dog in human years?
| Age of dog | Small 20 lb or less | Medium 21 to 50 lb | Large 51 to 100 lb | Giant 100+ lb |
|---|---|---|---|---|
| 1 year | 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 |
Between whole years the calculator interpolates in a straight line between the two chart rows and says so. Under 1 year and over 16 years the chart has no row, so a dash is shown. The AVMA rule the chart follows: 15 human years for a medium dog's first year, about 9 for the second, then roughly 5 per year, faster for larger dogs.
Sources: AKC: How to Calculate Dog Years to Human Years (chart and AVMA guideline) · Wang et al., Cell Systems 2020, doi:10.1016/j.cels.2020.06.006 · AVMA: Senior Pets
How It Works
Two published conversions run at once. The first is the American Kennel Club’s chart, which follows the American Veterinary Medical Association’s guideline: a medium dog’s first year is worth about 15 human years, the second about 9, and each year after that roughly 5, with giant breeds ageing faster. The chart is transcribed above exactly as the AKC publishes it, in four size classes by adult weight, from 1 to 16 years. Between whole years the calculator draws a straight line between the two rows and says so; under 1 year or over 16 it shows a dash because no row exists.
The second is the epigenetic clock from Wang et al. (Cell Systems, 2020): human age = 16 × ln(dog age) + 31. The researchers compared DNA methylation in 104 Labrador retrievers aged 0.1 to 16 years with human data. The formula is shown for dogs 1 year and older; below that it climbs steeply in a way the authors describe for puppyhood but that is not useful as a single number, so a dash is shown. Size does not enter the formula, so a small and a giant dog of the same age get the same result.
The two methods disagree most in early adulthood: a 2-year-old is 24 on the chart and about 42 on the clock. That gap is real and reflects two different questions (developmental milestones versus molecular ageing), not an error.
Worked Example
A 2-year-old medium dog (21 to 50 lb). AKC chart: the 2-year row reads 24 for small, medium and large dogs. Epigenetic clock: 16 × ln(2) + 31 = 16 × 0.693 + 31 = 42.1 human years.
FAQ
Why are the two numbers so different?
The chart is built from life-stage observations and vet guidance; the formula is fitted to changes in DNA methylation. The formula front-loads ageing (a 1-year-old is already 31) and flattens later, so it runs high for young adults and closer to the chart for seniors: a 12-year-old large dog is 77 on the chart and about 71 on the clock.
Which one should I use?
Use the chart when you want the familiar vet-style answer, especially for a large or giant breed, since size is part of it. Use the formula if you want the research-derived curve, remembering it came from one breed.
My dog is under a year old. Why the dashes?
The AKC chart starts at 1 year, and the formula was fitted across puppyhood where its value swings quickly with each month. Rather than invent a row, the calculator shows a dash and the explanation.
Where do the size bands come from?
They are the AKC chart’s own columns: 20 lb or less, 21 to 50 lb, 51 to 100 lb, and over 100 lb. The kg labels are conversions of those cut-offs.
Is this a veterinary assessment?
No. Both are population-level conversions. When your dog is considered senior, and what care that calls for, is a question for your vet; the AVMA notes small dogs are generally considered senior at about 7 and larger breeds at 5 to 6.
Sources
- AKC: How to Calculate Dog Years to Human Years - the size-by-age chart transcribed above and the AVMA 15 / 9 / 5 guideline
- Wang et al., Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome, Cell Systems 2020 - the human_age = 16 ln(dog_age) + 31 formula, 104 Labrador retrievers aged 0.1 to 16 years (open-access copy at PMC)
- AVMA: Senior Pets - when dogs of different sizes are considered senior