Compare dog years with human years
This calculator offers two age comparisons: a general medium-dog guideline and a separate Labrador research formula. Enter chronological age, select a method and view the result with the method’s assumptions visible. Neither output is a health score or a prediction of remaining life.
Our guide to dog-years conversion methods explains why the same dog can receive different human-equivalent numbers. You can compare the separate feline convention with the Cat Age Calculator.
General guideline
The reference points are approximately 15 human years at dog age one and 24 at age two. After age two, each additional dog year adds five: 24 + 5 × (dog age − 2). Decimal input between one and two is interpolated between the first two reference points.
A five-year-old dog gives 39 under this guideline. Five years and six months is 5.5 years and gives 41.5. This is a general comparison associated with medium-sized dogs, not a breed-specific conversion.
Labrador research comparison
The optional expression is 16 × ln(dog age) + 31. Here ln means the natural logarithm. The underlying research examined age-related DNA methylation in Labradors; this tool does not claim that the formula is validated for every breed.
At age five, the research expression gives approximately 56.8. It is not a correction proving that the general result of 39 is wrong; the models express different comparisons. The research option here accepts ages 1–16, while the general guideline accepts 1–30.
Input and interpretation
Convert extra months into a fraction of a year: years plus months divided by 12. Keep an estimated birthday labeled as estimated. The calculator does not infer breed, select a care schedule or measure biological age from an individual dog’s health records.
For puppy weight questions, use the Dog Size Calculator. For a recorded reproductive date, use the Dog Pregnancy Calculator. Find all related tools in Biology.
Frequently asked questions
Why are there two methods?
The general guideline and Labrador research formula describe different comparisons. Neither is an exact measurement of an individual dog’s biological age.
Can I use the research formula for every breed?
The underlying research used Labradors. This tool labels the method accordingly and does not claim validation for every breed.
How do I enter five years and six months?
Enter 5.5 years. Convert extra months by dividing by 12 and adding the result to the completed years.