Dog Age in Human Years
Convert a dog's age into human years with a breed-size adjustment.
About Dog Age in Human Years
A common estimate of dog age in human years is sixteen times the natural logarithm of the dog's age plus thirty-one. Breed size scales the result because larger breeds tend to age faster in human-equivalent terms. The old one-year-equals-seven rule is inaccurate for most of a dog's life. The logarithmic curve better captures the rapid aging of puppies and the slower aging of adults.
Formula
Dog Age in Human Years
Human years = 16 x ln(dog age) + 31, scaled by breed size
- ln
- the natural logarithm
- breed size
- small, medium or large scale factor
Worked example
With the default values below, Dog Age in Human Years returns Human Years of 56.8. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Dog ageminimum 0 years
- 5 years
- Breed sizeone of Small (under 20 lb), Medium (20-60 lb), Large (over 60 lb)
- Medium (20-60 lb)
Results
- Human Years
- 56.8
- First Two Years Equivalent
- 24.0
- Life Stage
- Senior
Step by step
- 1Values used
- 2Dog Age in Human Years
- 3Human Years= 56.8
- 4First Two Years Equivalent= 24.0
- 5Life Stage= Senior
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Dog Age in Human Years calculated?
Human years = 16 x ln(dog age) + 31, scaled by breed size A common estimate of dog age in human years is sixteen times the natural logarithm of the dog's age plus thirty-one. Breed size scales the result because larger breeds tend to age faster in human-equivalent terms.
Why does Dog Age in Human Years matter?
The old one-year-equals-seven rule is inaccurate for most of a dog's life. The logarithmic curve better captures the rapid aging of puppies and the slower aging of adults.
What values do I need to enter?
This calculator takes 2 inputs: Dog age, Breed size. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.