Growth and age
How old is my dog in human years?
This calculator uses 16 multiplied by the natural logarithm of dog age, plus 31, then rounds the result. It is a rough comparison based on Labrador research, not a universal biological age or a health assessment. It should not be read as an exact replacement for a dog's real life stage.
Why not simply multiply by seven?
The cited research compares age-related DNA methylation rather than assuming that every dog year corresponds to the same number of human years. The resulting relationship is nonlinear.
UC Davis explains the equation and also discusses other age-comparison approaches. Different methods answer different rough comparison questions; they need not produce the same number.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)
How does the formula behave?
The natural logarithm changes more rapidly at younger ages, so the curve rises differently from a straight line. At one year the logarithm is zero and the tool gives 31; at two years the rounded result is 42.
Those numbers describe the model. They do not mean a one-year-old dog has a particular human personality, emotional maturity or clinical condition.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)
What are the limits of the comparison?
The study described by UC Davis used Labrador retrievers, while breeds and individuals differ. The tool does not adjust the equation to every breed or use it to predict remaining lifespan.
Inputs run from one to twenty years with at most one decimal place. The curve above sixteen is shown as extrapolation beyond the oldest sampled dogs, so it should be read especially cautiously.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)
How should the example be used?
Enter two years to obtain the rounded comparison of 42 human years. Use the chart to see the shape of the model, not to decide care. Share and print are available; no device-save or calendar action is specified.
Worked example
Dog age 2 years
- Formula
- 16 x ln(2) + 31
- Rounded comparison
- 42 human years
A rough Labrador-based comparison, not a clinical age assessment.
Try it with your own details
Use the Dog age in human years to build your own result.
For general information only, not professional advice. Check the official sources below. Use your own judgement and speak to a qualified professional before you act.
Common questions
More answers on this topic.
Is the result a diagnosis of biological age?
No. It is a rough model-based comparison.
Does the same equation describe every breed exactly?
No. Its Labrador-based origin is an important limitation.
Why is part of the curve dashed?
Values above sixteen years extend beyond the oldest sampled dogs.
Can I use it to predict lifespan?
No. It does not estimate an individual dog's remaining lifespan or care needs.
Sources and checked dates
Each note explains what its source supports. Open the link to read the guidance yourself.
Confirms the natural-logarithm equation and explains the Labrador retriever study's breed limitation. Other age charts on this page are not used by this calculator.