How to use the dog age calculator
Pick Dog or Cat, then type the age in years and months, or switch to Birthday and choose the date. For a dog, tap a size or type the weight so the page can say when that size of dog is usually called a senior. The big number is the main answer. Under it every method shows its own number, and you can tap a method to make it the main one. The picture walks paw prints up your pet's age and lands each answer on a bar of human years, so the gap between the methods is easy to see. Watch how it works goes through the steps with your numbers. Nothing you type leaves your device unless you make a share link.
Three methods, three answers
There is no single right answer, because each method answers a slightly different question. The page names all three and does not hide the disagreement.
- The AVMA table. The American Veterinary Medical Association publishes a table for medium-sized dogs (21 to 50 pounds) and a rule for cats. A dog's first year counts as 15 human years and its second as 24. After that the table adds 4 to 6 human years per dog year and reaches 83 at year 15 and 87 at year 16. AVMA calls the figures approximate.
- The epigenetic formula. In 2020 a team led by Tina Wang compared how DNA methylation changes with age in dogs and in people and fitted a curve to it. The result is human age = 16 × ln(dog age) + 31.
- The 7× rule. The old rule of thumb. AVMA's senior pets page calls the seven-to-one idea a misconception. It is here only so you can see it next to the other two.
The formulas and a worked example
Epigenetic: human age = 16 × ln(dog age in years) + 31
7× rule: human age = 7 × dog age in years
Take a medium-sized dog that is 5 years old. The AVMA table gives 36. The formula gives 16 × ln(5) + 31, and since ln(5) is 1.6094, that is 16 × 1.6094 + 31 = 56.75, about 57. The 7× rule gives 7 × 5 = 35. Now make the dog 5 years 3 months old, which is 5 + 3 ÷ 12 = 5.25 years. AVMA lists 36 at year 5 and 42 at year 6, so a quarter of the way along is 36 + 0.25 × 6 = 37.5, shown as 38. The formula gives 16 × 1.6582 + 31 = 57.53, shown as 58, and the 7× rule gives 36.75, shown as 37. Between whole years the page draws that straight line itself, because AVMA's table has only whole-year rows. The calculator opens on the 5-year-old dog.
Where they disagree
The table shows medium-sized dogs. The three columns are the same dog read three ways.
| Dog age | 7× rule | AVMA table | Epigenetic formula |
|---|---|---|---|
| 1 | 7 | 15 | 31 |
| 2 | 14 | 24 | 42 |
| 3 | 21 | 28 | 49 |
| 5 | 35 | 36 | 57 |
| 8 | 56 | 51 | 64 |
| 10 | 70 | 60 | 68 |
| 12 | 84 | 69 | 71 |
| 15 | 105 | 83 | 74 |
The formula puts a 1-year-old dog at 31 and the AVMA table at 15. That is not an error in either. The formula matches molecular aging in blood to people and the table is a veterinary rule of thumb. The formula is also a straight line against the logarithm of age, so it climbs fast in the first years and slowly later. At 15 it says 74, well below the 7× rule's 105. It is not defined for very young puppies either: it crosses zero at about 0.144 years (around 7.5 weeks), so the page shows no formula number below 0.2 years.
Size and breed
AVMA's published table is for medium-sized dogs only. Its brochure says weight and breed may also matter but gives no numbers for other sizes or breeds, so the page does not invent any: it shows the same table for every size, with a note when your dog is not medium. The epigenetic study used one breed, Labrador retrievers, and its authors say breeds with very different lifespans could give different curves. What size does change, in AVMA's guidance, is when a dog is considered senior, roughly the last quarter of its expected life: small dogs (under 20 pounds) 8 to 11 years, medium (20 to 50) 8 to 10, large (50 to 90) 8 to 9 and giant (over 90) 6 to 7.
Cats
AVMA's rule for cats is the first year as 15 human years, the second as 24, then about 4 more for each year after: 36 at 5, 56 at 10 and 80 at 16. The page uses only that rule and the 7× rule for cats, because no cat formula from the epigenetic study was read. AVMA says cats are generally considered senior after age 10.
Life stages and your vet
The life stage label under the big number is simple: the first year, adult, then senior from the start of AVMA's range for your dog's size, or after 10 for a cat. It is a label, not a diagnosis. This page is for fun and for rough planning, not veterinary advice. Questions about food, vaccines, check-ups or whether your pet is aging well belong with your veterinarian.
Where the numbers come from
The table values and the cat rule are from AVMA's brochure "Pets age faster than people." The senior ages by size are from AVMA's "Caring for senior cats and dogs" page. The formula is from Wang and colleagues, Cell Systems, 2020, fitted on 95 Labrador retrievers aged about 0.1 to 16 years and compared with 320 people. The authors note that the data came from blood only. The page uses the formula as published and rounds the answers to whole human years. Past 16 years there is no AVMA row and the study ran out of dogs, so those answers are extrapolated or missing, and the page says so.
Questions
How old is a 1-year-old dog in human years?
AVMA's table says 15 for a medium-sized dog. The epigenetic formula says 31. The 7× rule says 7.
Is one dog year really seven human years?
No. It is a rule of thumb that does not match either the AVMA table or the epigenetic formula over a whole life. Dogs mature far faster than people in the first two years and more slowly after that.
Which method should I use?
The AVMA table is the veterinary rule of thumb and the page's default. The formula is the more recent research result but is built on one breed. Looking at both gives you a range.
Does my dog's size change the answer?
Not in the numbers, because AVMA gives a table only for medium-sized dogs. It changes when a dog counts as a senior: about 6 to 7 for giant dogs and 8 to 11 for small ones.
How old is a cat in human years?
By AVMA's rule a 2-year-old cat is 24, a 5-year-old is 36 and a 10-year-old is 56.
Can I use metric?
Yes. Press Metric to type your dog's weight in kilograms. The ages are the same either way.
Can I share my result?
Yes. Share makes a link with a picture for Facebook, X and Pinterest, a link you can copy, a Share button on phones and a short video for TikTok made on your device. The link keeps only the species, the age in months, the method and the size class, for 90 days. It never keeps a name, a weight or a birthday.