Dog Age Calculator
Updated
Quick answer
How old is my dog in human years?
A 1-year-old dog is roughly 15 in human years, and a 2-year-old is about 24. After that, each dog year adds about 4 to 5 human years for small and medium dogs, and up to 7 for giants. The old multiply-by-7 rule overestimates young dogs and underestimates seniors.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 5 years | 36 | 39 | 42 | 45 |
| 10 years | 56 | 64 | 72 | 80 |
Full chart for every age from 1 to 16 is just below.
What is dog age in human years?
Dog age in human years is an estimate of where your dog sits in their life compared to a person. Dogs mature far faster than humans early on: a one-year-old dog is roughly where a 15-year-old human is. After the second year the pace slows, and how much it slows depends on breed size, because larger dogs age faster than smaller ones.
That is why the old "multiply by seven" rule fails. It came from simple division (humans living to about 70, dogs to about 10) and it assumes dogs age at a constant rate. They do not: after age 2, one dog year adds 4 to 7 human years depending on size, and only giant breeds ever hit 7. For the full story behind the numbers, read how dog years actually work.
Dog age chart: dog years to human years, 1 to 16
Every age from 1 to 16, adjusted for size. Find your dog's row and you have your answer.
| Dog years | Toy & Small (up to 20 lb / 9 kg) | Medium (20–50 lb / 9–23 kg) | Large (50–90 lb / 23–41 kg) | Giant (90+ lb / 41+ kg) |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 31 |
| 4 | 32 | 34 | 36 | 38 |
| 5 | 36 | 39 | 42 | 45 |
| 6 | 40 | 44 | 48 | 52 |
| 7 | 44 | 49 | 54 | 59 |
| 8 | 48 | 54 | 60 | 66 |
| 9 | 52 | 59 | 66 | 73 |
| 10 | 56 | 64 | 72 | 80 |
| 11 | 60 | 69 | 78 | 87 |
| 12 | 64 | 74 | 84 | 94 |
| 13 | 68 | 79 | 90 | 101 |
| 14 | 72 | 84 | 96 | 108 |
| 15 | 76 | 89 | 102 | 115 |
| 16 | 80 | 94 | 108 | 122 |
We computed this table with the same rule the calculator's vet chart uses, following veterinary life-stage guidance2 and the pattern popularized by the American Kennel Club4: 15 for year one, 9 more for year two, then 4 to 7 per year by size. Toy and small breeds share a column because they age at the same chart rate. A 13-year-old giant breed passing "100" is why vets start watching large dogs so much earlier.
How to use this calculator
- Enter your dog's age in years. Use decimals for puppies, like 0.5 for six months.
- Pick the breed size that best matches your dog.
- Read the result: human years and life stage, updating as you type. Switch the conversion method to compare the vet chart with the epigenetic formula.
Dog years to human years formula
The vet chart (the calculator's default method) works like this:
- Year one counts as 15 human years.
- Year two adds 9 more (24 total).
- Every year after that adds 4 to 7 years, from small breeds to giant ones.
The epigenetic formula from the 2020 UC San Diego study is:human age = 16 × ln(dog age) + 31. It applies to dogs one year and older.
Why do big dogs age faster?
Among mammals, big species usually outlive small ones. Dogs flip that rule inside a single species: a Chihuahua often reaches 15 to 17 years, while a Great Dane averages 8 to 103. Researchers link this to faster growth and higher levels of the growth hormone IGF-1 in large breeds. Practically, it means size class changes the conversion after age 5, which is why our chart splits into four columns instead of pretending one line fits every dog.
When is my dog a senior?
Vets generally treat the last quarter of a breed's expected lifespan as senior2. As a rule of thumb:
| Size | Senior from (dog years) | That's roughly (human years) |
|---|---|---|
| Toy (<10 lb / 4.5 kg) | around 11 | about 60 |
| Small (10–20 lb / 4.5–9 kg) | around 10.5 | high 50s |
| Medium (20–50 lb / 9–23 kg) | around 9 | high 50s |
| Large (50–90 lb / 23–41 kg) | around 7.5 | high 50s |
| Giant (90+ lb / 41+ kg) | around 6 | low 50s |
Senior isn't a diagnosis, it's a schedule change: twice-yearly checkups, weight watching, and joint awareness. Talk to your vet about what's right for yours.
Example: a 5-year-old medium dog
Year one gives 15, year two adds 9 for a total of 24, and the remaining three years add 5 each for a medium breed:24 + 3 × 5 = 39 human years.
The epigenetic formula reads 16 × ln(5) + 31 ≈ 56.7, notably higher. It tracks molecular aging and was derived from Labradors, which is why we show it as a second opinion rather than the headline number.
How it works
Dogs pack most of their growing up into two years, then settle into a steady rhythm that runs faster for bigger breeds. Both of our methods describe that same curve; one reads it from decades of veterinary life-stage observation, the other from DNA.
The vet chart (our main result) is a size-adjusted table following the pattern used in veterinary life-stage guidance2: the first year counts as 15 human years, the second adds 9 (24 total), and every year after that adds 4 (toy and small breeds) up to 7 (giant breeds).
The epigenetic formula1 comes from comparing DNA methylation in dogs and humans:human age = 16 × ln(dog age) + 31. It only applies from age 1 up, and because it was derived from Labradors it tends to run high for young adult dogs. That is why the calculator shows it as a second opinion rather than the headline number.
Life stages (puppy, young adult, mature adult, senior, geriatric) follow the AAHA guidelines2, scaled to size-specific life expectancy: senior status starts around the last quarter of a breed's expected lifespan.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15, for every size class. A 1-year-old dog is roughly a human teenager: grown up on the outside, questionable decisions on the inside.
How old is 13 in dog years?
A 13-year-old small dog is about 68 in human years, a medium dog 79, a large dog 90, and a giant breed about 101. Size matters most at the top of the chart.
How many dog years is one human year?
There's no fixed number. Year one of a dog's life equals about 15 human years, but by age 10 each dog year equals only 4 to 7. On average across a lifetime it's close to 5.
Is one dog year really seven human years?
No. That rule assumes dogs age evenly, and they don't. A dog's first year equals roughly 15 human years, the second adds about 9 more, and each year after that adds 4 to 7 depending on breed size. A 2-year-old dog is about 24 in human years under the standard chart.
What is the epigenetic dog age formula?
In 2020, researchers at UC San Diego compared DNA methylation patterns in Labrador retrievers and humans and derived the formula: human age = 16 × ln(dog age) + 31. It applies to dogs one year and older and tracks biological aging rather than a simple chart average.
Why do the chart and the formula give different numbers?
They measure different things. The chart maps typical life-stage milestones by breed size. The epigenetic formula tracks molecular aging markers, and it was derived from one breed (Labradors), so it runs high for young adult dogs. We show both so you can see the range rather than a false single answer.
Do small dogs really live longer?
Yes, and by a lot. Small breeds routinely reach 14 to 17 years while giant breeds average 8 to 10. It's one of the strongest patterns in dog longevity data.
What's the oldest dog ever recorded?
Bluey, an Australian Cattle Dog from Victoria, Australia, lived 29 years and 5 months (1910 to 1939), per Guinness World Records. On the medium-dog chart that is about 161 in human years, after nearly two decades of herding cattle. A Portuguese dog named Bobi was briefly certified at 31 in 2023, but Guinness withdrew that record in 2024 after an investigation, so the century-old champion still stands.
References
- 1.Wang T, et al. (2020). Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome. Cell Systems 11(2). doi.org
- 2.American Animal Hospital Association (2019). Canine Life Stage Guidelines. aaha.org
- 3.Kraus C, Pavard S, Promislow DEL (2013). The size-life span trade-off decomposed: why large dogs die young. The American Naturalist 181(4). doi.org
- 4.American Kennel Club. How to Calculate Dog Years to Human Years. akc.org
- 5.Guinness World Records. Oldest dog ever (Bluey, 29 years 5 months). guinnessworldrecords.com
