Dog Age Calculator (Dog Years to Human Years)
Convert your dog's age to human years by size class (small, medium, large, giant) with the veterinary table used by the AVMA and AKC, or with the 2020 DNA-methylation formula 16 × ln(age) + 31. Accepts years, months or weeks for puppies.
Last updated: October 2026
Human-equivalent age
36 human years
Formula below · 4 sources (pmc.ncbi.nlm.nih.gov, avma.org, akc.org, aaha.org) · Updated Oct 2026
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About this calculator
The old rule that one dog year equals seven human years is wrong at both ends: dogs are sexually mature and physically adult by one to two years, then age more slowly, and how fast they age depends on their adult size. This page gives two estimates.
Veterinary size table (default). The table used by the American Veterinary Medical Association and the American Kennel Club puts a dog's first year at about 15 human years and the second at about 9 more (24 at age 2), then adds roughly 4 human years per dog year for small dogs, 5 for medium, 6 for large and 7 for giant breeds. Giant breeds start a little behind (12 at one year, because they mature later) but overtake every other class by age 3; a 10-year-old Great Dane is about 79 in human terms while a 10-year-old Chihuahua is about 56. Between whole years the calculator interpolates, under one year it scales from 0 at birth, and beyond 16 it keeps adding the last yearly step.
DNA methylation clock. A 2020 study (Wang et al., Cell Systems) compared age-related methylation changes in the DNA of 104 Labrador retrievers with human data and fitted human age = 16 × ln(dog age) + 31. It says a 1-year-old dog is already about 31, a 2-year-old 42, a 5-year-old 57 and a 10-year-old 68: the curve is steep early (reflecting the rapid molecular changes of puppyhood) and very flat later. It was built from one medium-large breed, so it has no size adjustment, and it is not meant for puppies under a year (the calculator scales linearly from 0 to 31 there).
The two methods disagree most for young adult dogs (a 3-year-old is 28 by the table and 49 by the DNA clock) and converge in old age; both appear as tiles whichever you pick. Neither is a health assessment. AAHA's canine life-stage guidelines define the stages by size instead of a single age: puppy (to 6-9 months), young adult (to 3-4 years), mature adult (to the last 25% of the breed's expected lifespan) and senior (the last quarter), which is why a 7-year-old giant breed is "senior" while a 7-year-old toy breed is barely middle-aged. Ask your veterinarian when to start senior screening for your dog's breed.
Dog years to human years by size class (AVMA/AKC table) and by the DNA clock
Scroll sideways to see all columns →
| Dog's age | Small (≤20 lb) | Medium (21-50 lb) | Large (51-90 lb) | Giant (>90 lb) | DNA clock |
|---|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 | 31 |
| 2 | 24 | 24 | 24 | 22 | 42 |
| 3 | 28 | 28 | 28 | 31 | 49 |
| 4 | 32 | 32 | 32 | 38 | 53 |
| 5 | 36 | 36 | 36 | 45 | 57 |
| 6 | 40 | 42 | 45 | 49 | 60 |
| 7 | 44 | 47 | 50 | 56 | 62 |
| 8 | 48 | 51 | 55 | 64 | 64 |
| 9 | 52 | 56 | 61 | 71 | 66 |
| 10 | 56 | 60 | 66 | 79 | 68 |
| 11 | 60 | 65 | 72 | 86 | 69 |
| 12 | 64 | 69 | 77 | 93 | 71 |
| 13 | 68 | 74 | 82 | 100 | 72 |
| 14 | 72 | 78 | 88 | 107 | 73 |
| 15 | 76 | 83 | 93 | 114 | 74 |
| 16 | 80 | 87 | 99 | 121 | 75 |
How to use
Enter the dog's age (in years, months or weeks), choose its adult size class, and pick the method. Example 1 (defaults): a 5-year-old medium dog (21-50 lb). Table: 36 human years. DNA clock: 16 × ln(5) + 31 = 16 × 1.609 + 31 = 56.8, so 57 (shown as a tile). Example 2: a 10-year-old giant breed. Table: 79; small breed at the same age: 56. Example 3: a 7.5-year-old large dog. Halfway between year 7 (50) and year 8 (55): 52.5, shown as 53. Example 4: a 16-week-old puppy. 16 ÷ 52.18 = 0.31 years; table: 0.31 × 15 = 4.6, so about 5 human years; DNA clock: 0.31 × 31 = 9.5, so about 10. Example 5: a 20-year-old small dog. 80 at 16, then 4 per year: 96.
Frequently asked questions
How many human years is one dog year?
It depends on the age and the size. The first dog year is worth about 15 human years, the second about 9, and each year after that about 4 for small dogs up to 7 for giant breeds. The DNA-clock formula gives even more weight to the first year (31) and much less to later ones.
Why do big dogs age faster?
Large and giant breeds live shorter lives on average (a Great Dane 7-10 years, a Chihuahua 14-17), so each calendar year is a bigger share of their lifespan. Studies of breed longevity find roughly a month of life expectancy lost per 2 kg (4.4 lb) of adult body mass, though the mechanism is still debated.
Which method should I use?
The size table is the better everyday guide because it accounts for breed size and is what veterinarians quote. The DNA clock is a research result from one breed; it is a good illustration of how fast puppies mature at the molecular level, but it rates every 3-year-old as 49 regardless of size.
When is my dog a senior?
AAHA defines senior as the last quarter of a breed's expected lifespan: from about 11-12 years for small breeds, 10 for medium, 8 for large and 6-7 for giant breeds. Veterinarians often suggest twice-yearly check-ups and blood work from then on.
How old is a puppy in weeks or months?
Enter the age in weeks or months and the calculator converts it (52.18 weeks or 12 months to a year). A 6-month-old puppy is 0.5 years, about 7.5 human years by the table or 15.5 by the DNA clock; developmentally it is roughly a human adolescent, which is why training and socialisation matter so much in the first year.
Related calculators
Sources & references
- AVMA: How old is a dog in human years? (size-class table and why 7:1 is wrong)
- American Kennel Club: How to calculate dog years to human years (size-class chart)
- Wang et al. (2020), Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome, Cell Systems
- AAHA: 2019 Canine Life Stage Guidelines (life stages defined by breed size)
- AVMA: Senior pets (when dogs and cats are considered senior)
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