Pet Age Calculator (Dog + Cat Years)
Quick dog-or-cat converter to human years. Dogs use the 2020 DNA-methylation formula (16 × ln(age) + 31); cats use the veterinary life-stage chart. For size-class dog ages and kitten ages in weeks, see the separate dog and cat calculators.
Last updated: October 2026
Human-equivalent age
57 human years
Formula below · 3 sources (pmc.ncbi.nlm.nih.gov, aaha.org, vet.cornell.edu) · Updated Oct 2026
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About this calculator
The old rule that one dog year equals seven human years does not hold: dogs and cats grow up very fast in their first year or two, then age more slowly.
Dogs
Human age ≈ 16 × ln(dog age) + 31, for dogs 1 year and older.
This comes from a 2020 study (Wang et al., Cell Systems) that matched age-related chemical changes in the DNA of Labrador retrievers and people. A 1-year-old dog maps to about 31, a 2-year-old to 42, a 5-year-old to 57 and a 10-year-old to 68. The log curve breaks down for young puppies, so under 1 year the calculator scales straight from 0 at birth to 31 at the first birthday.
Cats
About 15 human years at age 1, 24 at age 2, then 4 human years for each year after that. This is the life-stage chart used in feline care guidelines; a 10-year-old cat is about 56 and a 15-year-old about 76.
With the default, a 5-year-old dog is 16 × ln(5) + 31 = 56.8, shown as 57 human years.
These are averages. Size matters a lot for dogs: large and giant breeds age faster and have shorter lives than small breeds, and the study used a single mid-size breed. Treat the result as a fun guide, not a health assessment, and ask your veterinarian when to start senior care.
For a size-adjusted dog age (the AVMA/AKC table, where a giant breed ages faster than a toy breed) use the dog age calculator, and for kitten ages in weeks or months and the AAFP life stages use the cat age calculator; both are linked below.
Pet age in human years
Scroll sideways to see all columns →
| Pet's age | Dog (16 × ln(age) + 31) | Cat (life-stage chart) |
|---|---|---|
| 1 year | 31 | 15 |
| 2 years | 42 | 24 |
| 3 years | 49 | 28 |
| 5 years | 57 | 36 |
| 7 years | 62 | 44 |
| 10 years | 68 | 56 |
| 12 years | 71 | 64 |
| 15 years | 74 | 76 |
| 18 years | 77 | 88 |
How to use
Choose dog or cat and enter the age in years. Use decimals for part years: 1.5 for 18 months, 0.5 for 6 months. Example 1 (default): a 5-year-old dog. 16 × ln(5) + 31 = 16 × 1.609 + 31 = 56.8, so about 57. Example 2: a 12-year-old dog. 16 × ln(12) + 31 = 70.8, so about 71. Example 3: a 10-year-old cat. 24 + (10 − 2) × 4 = 56. Example 4: a 6-month-old puppy (0.5). 0.5 × 31 = 15.5, shown as 16.
Frequently asked questions
Is one dog year really seven human years?
No. Dogs mature far faster at first: by the DNA-based formula a 1-year-old dog is already about 31 in human terms. After that, aging slows, so a 10-year-old dog is about 68, not 70, and a 15-year-old about 74, not 105.
Does my dog's size matter?
Yes. Large and giant breeds age faster and typically live shorter lives than small breeds. The formula was built from Labrador retrievers, so read the result as a little young for a Great Dane and a little old for a Chihuahua.
How are cat years calculated?
A cat reaches about 15 human years in its first year and 24 by its second; after that each cat year adds about 4 human years. Indoor cats commonly live 15 to 20 years, roughly 76 to 96 in human terms.
When is my pet a senior?
Many vets treat cats as seniors from about 10 years and dogs from about 7, earlier for large breeds. Ask your veterinarian; they may suggest more frequent checkups as your pet ages.
Is there a version that accounts for dog size?
Yes: the dog age calculator uses the veterinary table with four size classes (small, medium, large, giant) alongside the DNA formula shown here, and the cat age calculator shows the AAHA/AAFP life stage for a cat's age entered in years, months or weeks.
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Sources & references
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