Updated · Published by Radif Partners
Dog age calculator: your dog's age in human years
Two answers side by side, the size chart veterinarians use and the 2020 DNA-methylation formula, with the senior age for your breed.
AKC size chart · Wang et al. 2020 · AVMA senior ages · checked
A five-year-old medium dog is about 36 in human years, and a ten-year-old giant breed is already around 79: the conversion depends on size, not on a fixed multiplier. This calculator reads the chart the American Kennel Club publishes by weight class, where every dog counts as fifteen at its first birthday and the curves then fan out, slowly for a Chihuahua and steeply for a Great Dane. Next to it, it shows the result of the formula a University of California San Diego team derived in 2020 from the DNA methylation of 104 Labrador Retrievers, which compresses the first year far more and stretches the later ones less. Neither figure is a medical age. What matters for care is the point where your dog enters the last quarter of its expected life, and that is the line the result card gives you, from your breed's life span when you choose one, or from the AVMA ranges by size when you do not.
Runs in your browser: nothing you type is sent or stored. Human-year figures are comparisons, not a health assessment. How the figures are built.
Why size changes the answer
Small and large dogs grow up at the same pace and then part company. On the chart, a two-year-old is 24 whether it weighs eight pounds or eighty, but by ten the small dog sits at 56 and the large one at 66. Giant breeds run a different curve from the start: slightly younger at one (12) and then, after the first few years, mostly seven or eight human years per calendar year, which is why a Mastiff is gray at the muzzle when a Jack Russell of the same age still behaves like an adolescent.
The pattern matches what kennel clubs and longevity studies report about life span: bigger breeds live shorter lives, so each of their years represents a larger share of the whole. A conversion that ignores size gets the small dogs too old and the giants too young, and the error grows every year.
The DNA-methylation formula, and what it is good for
In 2020, Wang and colleagues compared the methylation marks that accumulate on DNA with age in dogs and in humans and fitted a single curve: human age = 16 × ln(dog age) + 31. A one-year-old comes out at 31, a two-year-old near 42, and after that the curve flattens: a twelve-year-old lands around 71.
The formula captures something the chart does not, namely how fast a puppy matures. Dogs reach puberty within months, and by one year their bodies are closer to a young adult human than to a teenager. It was built on a single breed, though, so it cannot tell a toy dog from a giant one. Read it as a description of early development, and use the size chart for the later years, where breed size dominates.
When your dog becomes a senior
The AVMA does not give dogs one senior age. It suggests treating a dog as senior once it enters the last quarter of the life span expected for its breed, which on average means 8 to 11 years for small or toy breeds, 8 to 10 for medium ones, 8 to 9 for large ones and 6 to 7 for giants.
When you pick a breed, the calculator takes the middle of that breed's life span from our breed pages and places the senior line at three quarters of it. A Labrador with an 11 to 13 year expectancy turns senior at about nine, a Great Dane much earlier. Senior is the stage at which twice-yearly checkups and blood work start to pay for themselves, not a label for a dog that has slowed down.
How to read an age between two birthdays
The chart gives whole years only. For an age such as five years and seven months, the calculator moves in a straight line between the fifth and sixth birthday values; before the first birthday it climbs from zero to the year-one value. Beyond sixteen, where the chart stops, it keeps adding the last yearly step of the column, which is an extension rather than published data.
For mixed breeds, weigh the dog when it is lean and choose the size column that matches. A 45 lb shepherd mix belongs with the medium dogs; a 70 lb one with the large dogs, even if its parents were of different sizes.
Dog years to human years, AKC chart by size
| Dog's age | Small (≤20 lb) | Medium (21–50 lb) | Large (51–100 lb) | Giant (100+ lb) |
|---|---|---|---|---|
| 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 |
Values as published by the American Kennel Club. The calculator interpolates between them.
Not a substitute for a veterinarian
A human-year figure is a way to picture where your dog stands in life. It says nothing about the health of the individual animal: a vet's examination, weight history and blood work tell you that.
Sources
- American Kennel Club, chart of dog years to human years by size, with the AVMA rule (read October 11, 2026)
- Wang et al., Cell Systems (2020), dog-to-human age formula from DNA methylation (read October 11, 2026)
- AVMA, Caring for senior cats and dogs, when dogs and cats are considered senior (read October 11, 2026)