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Dog Age Calculator

How old is your dog in human years? See the answer three ways, side by side, with each formula shown: the AVMA guideline, the UC San Diego DNA formula, and the old 7× rule.

Enter your dog’s age to see it in human years, three ways.

Estimate. A real-world figure based on the assumptions listed below, which you can change.

How this calculator works

There is no single conversion from dog years to human years, because dogs do not age at a steady rate. They grow up fast, reaching the equivalent of adolescence within a year, then age more slowly. So the calculator shows the three methods people use and where each comes from.

The AVMA guideline, published by the American Kennel Club: the first year of a medium-sized dog’s life is about 15 human years, the second about 9 more, and each year after about 5. A 4-year-old dog is about 15 + 9 + 5 + 5 = 34.

The UC San Diego formula: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. Researchers derived it in 2020 by comparing age-related changes in DNA in 104 Labrador retrievers with the same changes in people. It puts a 1-year-old dog at 31 and a 4-year-old at about 53.

The 7× rule multiplies by seven. It has been popular since the 1950s but has no science behind it, and it understates how fast puppies mature. It is shown so you can compare.

The formula

Exactly what happens to your numbers, step by step.

AVMA guideline

first year: 15 × age
second year: 15 + 9 × (age − 1)
after that: 24 + 5 × (age − 2)

UC San Diego (2020)
```
human age = 16 × ln(dog age) + 31
```
7× rule
```
human age = dog age × 7
```

A worked example

A 4-year-old dog.

What you enter

Age: 4 years

Step by step

AVMA guideline: 15 + 9 + 5 × (4 − 2) = 34
UC San Diego: 16 × ln(4) + 31 = 16 × 1.386 + 31 = 53.2
7× rule: 4 × 7 = 28

About 34 by the AVMA guideline or 53 by the UC San Diego formula; 28 by the 7× rule

The methods disagree most in early adulthood. The DNA-based formula says a young adult dog is further along than either rule suggests, and the gap narrows in old age, when the formula slows down.

Dog years to human years, worked out

Common ages, each by all three methods.

1.How old is a 1-year-old dog in human years?
1. 15 × 1 = 15
2. 16 × ln(1) + 31 = 16 × 0.000 + 31 = 31
About 15 by the AVMA guideline or 31 by the UC San Diego formula, against 7 by the 7× rule.
2.How old is a 2-year-old dog in human years?
1. 15 + 9 × (2 − 1) = 24
2. 16 × ln(2) + 31 = 16 × 0.693 + 31 = 42.1
About 24 by the AVMA guideline or 42 by the UC San Diego formula, against 14 by the 7× rule.
3.How old is a 7-year-old dog in human years?
1. 15 + 9 + 5 × (7 − 2) = 49
2. 16 × ln(7) + 31 = 16 × 1.946 + 31 = 62.1
About 49 by the AVMA guideline or 62 by the UC San Diego formula, against 49 by the 7× rule.
4.How old is a 10-year-old dog in human years?
1. 15 + 9 + 5 × (10 − 2) = 64
2. 16 × ln(10) + 31 = 16 × 2.303 + 31 = 67.8
About 64 by the AVMA guideline or 68 by the UC San Diego formula, against 70 by the 7× rule.
5.How old is a 6-month-old puppy in human years?
1. 15 × 0.5 = 7.5
2. 16 × ln(0.5) + 31 = 16 × −0.693 + 31 = 19.9
About 8 by the AVMA guideline or 20 by the UC San Diego formula, against 4 by the 7× rule.

Results are rounded to the nearest whole year. The AVMA guideline is for a medium-sized dog; the UC San Diego formula was built from Labrador retrievers.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

The AVMA guideline is for a medium-sized dog. Small dogs tend to live longer and large breeds shorter, so a large dog ages faster in later years and a small dog slower.
The guideline gives whole years. Within the first two years the calculator spreads each year’s human-age equivalent evenly, which is its own simplification.
The UC San Diego formula is shown from two months of age: below about seven and a half weeks it gives a figure below zero.

What this cannot tell you

The UC San Diego formula was built from a single breed, Labrador retrievers, aged up to 16. The researchers expect it to apply more widely, but that has not yet been shown.
None of these methods tells you how healthy your dog is. Ask your vet about senior care: many small dogs are considered seniors around 7, and larger breeds earlier.

Questions people ask

Is one dog year really seven human years?

No. The 7× rule is a rough average with no science behind it. Dogs mature much faster than that at first: by most estimates a 1-year-old dog is roughly a teenager or young adult in human terms, not a 7-year-old child. Aging then slows down.

How do you calculate a dog’s age in human years?

By the AVMA guideline, count 15 for the first year, 9 for the second, and about 5 for each year after: a 6-year-old dog is 15 + 9 + 4 × 5 = 44. By the UC San Diego formula, multiply the natural logarithm of the dog’s age by 16 and add 31: for a 6-year-old that is about 60.

Does breed or size change a dog’s age in human years?

Yes. Small dogs usually live longer than large ones, so after the first couple of years a large dog ages faster in human terms. The AVMA guideline is pitched at a medium-sized dog, and the UC San Diego formula comes from Labrador retrievers, so treat either as an estimate for your dog.

Where does the formula 16 ln(age) + 31 come from?

From a 2020 study in the journal Cell Systems by researchers at UC San Diego. They tracked chemical changes to DNA that accumulate with age, called methylation, in 104 Labrador retrievers, matched them to the same changes in humans, and fitted a curve to the result.

Sources and review

Sources

Methodology version 1.0.0 · Last reviewed October 12, 2026

Cite this calculator

For coursework, a resource list or your own site. How every calculator is built and checked is set out on the methodology page.

Citation

Chalk Calculator. (2026, October 12). Dog Age Calculator (Methodology version 1.0.0). https://chalkcalculator.com/dog-age-calculator/

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