Dog Age Calculator
Dog Age Calculator
Convert your dog’s age to human years by size, using the veterinary chart the American Kennel Club publishes, and compare it with the DNA based formula from the University of California San Diego and the old seven year rule, which gets young and old dogs wrong.
Human years through a dog’s life, by size
Three ways to count
The size chart is the one published by the American Kennel Club, following the American Veterinary Medical Association’s guide that a medium dog’s first year equals about 15 human years, the second about 9 more, and each year after about 5, with small dogs aging more slowly and large and giant dogs faster in later life. Ages between whole years are interpolated; under a year the page scales the first year evenly, and past 16 it continues the last yearly step. The DNA formula, human age = 16 x ln(dog age) + 31, comes from a 2020 University of California San Diego study of DNA methylation in Labrador retrievers. All three are estimates; breed, health and care make every dog different. The CSV, image and printed report contain the values you entered, nothing preloaded.
How to use this tool
Enter your dog's age in years, add any months, and pick its size as a grown dog, even if it is still a puppy. The age in human years appears at the top, with the DNA based estimate and the seven year rule beside it for comparison, and the cards on the right show the same age for the other sizes.
The line chart shows how each size ages through life, with your dog marked, and the table below it is the full chart from 1 to 16 years.
How dog years are worked out
Dogs mature fast. The American Veterinary Medical Association's guide, which the American Kennel Club chart follows, puts a medium dog's first year at about 15 human years and the second at about 9 more, so a 2 year old dog is roughly 24. After that each dog year adds about 4 to 7 human years, depending on size.
Size matters because big dogs have shorter lives. Up to about age 5 the sizes are close together, but from then on a giant dog races ahead: at 10 it is about 79 in human years, a large dog 66, a medium dog 60 and a small dog 56. The calculator reads the chart for your dog's size and interpolates between whole years.
Dog age chart by size
| Dog age | Small 20 lb or less | Medium 21 to 50 lb | Large 51 to 100 lb | Giant over 100 lb | DNA formula |
|---|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 12 | 31 |
| 2 years | 24 | 24 | 24 | 22 | 42 |
| 3 years | 28 | 28 | 28 | 31 | 49 |
| 4 years | 32 | 32 | 32 | 38 | 53 |
| 5 years | 36 | 36 | 36 | 45 | 57 |
| 6 years | 40 | 42 | 45 | 49 | 60 |
| 7 years | 44 | 47 | 50 | 56 | 62 |
| 8 years | 48 | 51 | 55 | 64 | 64 |
| 9 years | 52 | 56 | 61 | 71 | 66 |
| 10 years | 56 | 60 | 66 | 79 | 68 |
| 11 years | 60 | 65 | 72 | 86 | 69 |
| 12 years | 64 | 69 | 77 | 93 | 71 |
| 13 years | 68 | 74 | 82 | 100 | 72 |
| 14 years | 72 | 78 | 88 | 107 | 73 |
| 15 years | 76 | 83 | 93 | 114 | 74 |
| 16 years | 80 | 87 | 99 | 121 | 75 |
Human years by adult size, from the chart the American Kennel Club publishes; last column from the 2020 UC San Diego DNA methylation formula for Labradors.
A worked example you can check on paper
A spaniel that weighs 35 lb is a medium dog. At 7 years old the chart gives 47 human years, about the same as the seven year rule's 49 at this age. At 2 years 6 months, halfway between the chart's 24 at two and 28 at three, it would be about 26, where the seven year rule says only 17 or 18.
The DNA formula puts the 7 year old at 16 times the natural log of 7, which is 1.946, plus 31: about 62. The formula runs ahead of the chart in the middle years and behind it for very old small dogs.
Mistakes that catch people out
Using the puppy's current weight. Size means the adult weight; a 10 lb Great Dane puppy is still a giant dog.
Taking the answer too literally. These are averages. A lean, active 12 year old terrier may be in better shape than a heavy 8 year old of the same size.
Waiting for signs of age. Dogs hide discomfort well. Regular checkups from middle age catch problems before they show.
Popular calculations
Each opens the calculator with its own address, and every value can be changed once it is open.
Medium dogs, 21 to 50 lb
Small dogs, 20 lb or less
Large dogs, 51 to 100 lb
Giant dogs, over 100 lb
Puppies
How this was checked
The engine was tested in Node against every whole year of the published chart for all four sizes, against hand interpolation between years, and against the UC San Diego formula: 16 times ln(7) plus 31 is 62.1 and 16 times ln(1) plus 31 is 31.
Every address in the lists above was then opened and checked for a distinct title, the right answer, charts that render, and clean CSV, image and print output containing only that calculation, at desktop, tablet and phone widths.
Common questions
How old is my dog in human years?
Use the size chart: a dog's first year equals about 15 human years and its second about 9 more, so a 2 year old dog is about 24. After that small dogs add about 4 human years a year, medium dogs 4 to 5, large dogs 5 to 6 and giant dogs 7 or more. A 7 year old medium dog is about 47.
Is one dog year really seven human years?
No. The seven year rule makes young dogs too young, a 1 year old dog is already about 15 in human terms, not 7, and makes old small dogs too old. It persists because it roughly matches over a medium dog's whole life.
Why do big dogs age faster?
Large and giant breeds grow quickly and have shorter lives on average, so each year after about the fifth counts for more human years. On the chart a 10 year old giant dog is about 79, while a 10 year old small dog is about 56.
What is the DNA formula for dog age?
A 2020 study at the University of California San Diego matched chemical changes on the DNA of Labrador retrievers to those in people and proposed human age = 16 x ln(dog age) + 31. It suggests young dogs age even faster than the chart, a 1 year old at about 31, then slow down, but it was based on one breed.
When is a dog a senior?
The American Animal Hospital Association treats the last quarter of a dog's expected life span as its senior years. That comes earlier for large and giant breeds than for small dogs, which may live well into their teens.
How old is a 6 month old puppy in human years?
Roughly 6 to 8 by the size chart scaled through the first year, though puppies develop unevenly: by 6 months many are near adolescence in behavior. By the first birthday most dogs are about as mature as a 15 year old person.
Related Calculators and Reference
- Age Calculator: exact age from a birth date.
- Date Difference Calculator: days, weeks and months between two dates.
- Grams to Ounces Converter: weighing dog food.
- Sleep Calculator: bedtimes for the humans in the house.
- Puppy Weight Calculator: predict adult weight and growth from age and weight.
- Dog Food Calculator: work out daily calories and how much to feed.
- Cat Age Calculator: the cat version of the same conversion.
- American Kennel Club: How to Calculate Dog Years to Human Years: the chart and the veterinary guidance behind it.