Medium dog, 7 years
- Pet
- Dog
- Age
- 7
- Age in
- Years
- Adult weight
- Medium (21–50 lb / 9.5–22.7 kg)
- Method
- Size chart (AAHA)
- Age in human years
- 47 years
Checked against: AAHA/Zoetis 2019 chart: 7 years, 21–50 lbs = 47
Dog years and cat years calculator
Dog years and cat years calculator: a pet's age in human years from the AAHA/Zoetis size chart or the International Cat Care table, for fun comparisons.
By AdminDrafted with AI writing toolsUpdated Checked examples: 8
Age in human years
years
Age in human years: 47 years
A medium dog of 7 years is about 47 in human years. Bigger dogs age faster after their second year, which is why the lines spread apart.
Dog age in human years
SmallLargeGiantMedium (your dog)
How it's calculated S
Read the AAHA chart (medium (21–50 lb / 9.5–22.7 kg))
Between chart rows the value is interpolated in a straight line.
About the dog years and cat years calculator
A dog's age is read off the AAHA/Zoetis physiological age chart for its adult weight (up to 20 lb, 21–50 lb, 51–90 lb or over 90 lb) and a cat's off the International Cat Care table, with straight-line interpolation between rows. For dogs there is also the DNA methylation formula of Wang et al. (2020): human age = 16 ln(dog age) + 31.
On the chart every dog counts as 15 at one year and 24 at two. After that larger dogs age faster, so a 7-year-old medium dog is 47 while a 7-year-old giant dog is 56. Cats count as 15 at one year, 24 at two and 4 more for each year after, so a 10-year-old cat is 56.
Human-year figures are a way to picture life stage, not a health check, and they come from population charts rather than from your own pet. The methylation formula was fitted on 104 Labrador retrievers and ages young dogs faster than the chart does.
How to convert dog years to human years
On the AAHA/Zoetis physiological age chart, every dog equals 15 human years at age 1 and 24 at age 2, and larger dogs age faster after that. A 7-year-old medium dog (21–50 lb) is 47 in human years, while a 7-year-old giant dog is 56. The old seven-times rule would say 49 for both.
Dog years by size: the AAHA/Zoetis chart
Values from the AAHA/Zoetis chart (2019), by the dog's adult weight:
- Small, up to 20 lb (9 kg): 5 years = 36, 7 = 44, 10 = 56, 12 = 64, 15 = 76.
- Medium, 21–50 lb (9.5–22.7 kg): 5 years = 37, 7 = 47, 10 = 60, 12 = 69, 15 = 83.
- Large, 51–90 lb (23–40.8 kg): 5 years = 40, 7 = 50, 10 = 66, 12 = 77, 15 = 93.
- Giant, over 90 lb (40.8 kg): 5 years = 42, 7 = 56, 10 = 78, 12 = 93, 15 = 115.
The chart runs to 20 years for small, medium and large dogs and to 16 years for giant dogs.
Ages between rows, puppies and very old dogs
- Between rows, the value follows a straight line. A small dog of 3.5 years sits halfway between 28 at age 3 and 32 at age 4, so it counts as 30.
- Under 1 year, the chart has no rows, so the line runs from 0 at birth to 15 at age 1. A 6-month-old puppy comes out at 7.5; that line is an assumption added to the chart.
- Past the last row, the final year's step continues and the result is an extrapolation. A 17-year-old giant dog comes out at 131.
The DNA methylation formula for dogs
Wang et al. (2020), in Cell Systems, compared DNA methylation in 104 Labrador retrievers with human data and fitted human age = 16 × ln(dog age) + 31.
- 1 year: 31 (chart: 15)
- 2 years: 42.1 (chart: 24)
- 7 years: 62.1 (medium chart: 47)
- 12 years: 70.8 (medium chart: 69)
The formula ages young dogs much faster than the chart, then flattens out. It was fitted on one breed, so it is a rough guide for others. Below about 7.5 weeks (0.144 years) it gives a negative age.
The chart and the formula are separate models. Averaging their answers gives a number neither of them supports.
How to convert cat years to human years
International Cat Care counts a cat's first year as 15 human years and its second as 9 more, so a 2-year-old cat is 24. Each year after that adds 4: a 10-year-old cat is 24 + 8 × 4 = 56, and a 15-year-old is 76.
The first year rises unevenly: 1 month is 1, 3 months 4, 6 months 10, 7 months 12 and 12 months 15. Between those points the value follows a straight line, so 9 months comes out at 13.2. The table continues to 25 years, which is 116.
Cat life stages
International Cat Care groups cats into six stages:
- Kitten: up to 6 months
- Junior: 7 months to 2 years
- Adult: 3 to 6 years
- Mature: 7 to 10 years
- Senior: 11 to 14 years
- Super senior: 15 years and older
An 11-year-old cat, at the start of the senior stage, is 60 in human years.
Example ages
| Scenario | Human-age result | Dog chart comparison | Cat stage |
|---|---|---|---|
| Default | 47.000000 | — | — |
| Giant ten years | 78.000000 | — | — |
| Small midpoint | 30.000000 | — | — |
| DNA seven years | 62.134562 | 47.000000 | — |
| Six month kitten | 10.000000 | — | Kitten |
- Default: a 7-year-old medium dog on the chart. Giant ten years: a 10-year-old dog over 90 lb.
- Small midpoint: the 3.5-year-old small dog.
- DNA seven years: the formula at 7 years, with the medium chart's 47 beside it.
- Six month kitten: 10 human years, in the kitten stage.
A dash means the column does not apply to that pet or method.
Entering your pet's age
- Choose years or months: 7 months and 7 years are very different ages. Either unit goes up to 40, so enter an older pet in years. If you know the birth date but not the age, the age calculator gives it in years and months, and the days between dates calculator counts from an adoption day.
- Pick the size group from the dog's adult weight. For a puppy, use the weight it is expected to reach, not its weight today.
- Size changes only the chart figure; the DNA formula gives the same answer for every size.
What human years can tell you
Both charts and the formula describe populations. They help picture a life stage but cannot show how healthy one animal is or how long it will live; a veterinary exam answers those questions.
Worked examples
Giant dog, 10 years
- Pet
- Dog
- Age
- 10
- Age in
- Years
- Adult weight
- Giant (over 90 lb / 40.8 kg)
- Method
- Size chart (AAHA)
- Age in human years
- 78 years
Checked against: AAHA/Zoetis 2019 chart: 10 years, >90 lbs = 78
Small dog, 3½ years (between rows)
- Pet
- Dog
- Age
- 3.5
- Age in
- Years
- Adult weight
- Small (up to 20 lb / 9 kg)
- Method
- Size chart (AAHA)
- Age in human years
- 30 years
Checked against: AAHA/Zoetis chart rows 28 (3 y) and 32 (4 y), midpoint
Large dog at the last chart row
- Pet
- Dog
- Age
- 20
- Age in
- Years
- Adult weight
- Large (51–90 lb / 23–40.8 kg)
- Method
- Size chart (AAHA)
- Age in human years
- 120 years
Checked against: AAHA/Zoetis 2019 chart: 20 years, 51–90 lbs = 120
Questions
Is one dog year really seven human years?
No. On the AAHA/Zoetis chart every dog reaches the equivalent of 15 human years at age one and 24 at age two, then ages 4 to 8 human years a year depending on size. A 10-year-old dog is 56 if it weighs 20 lb or less but 78 if it weighs over 90 lb; the seven-year rule gives 70 for both.
How old is my cat in human years?
International Cat Care counts a cat's first two years as 24 human years (6 months is about 10 and 1 year about 15) and each year after that as 4. A 10-year-old cat is 56 and a 15-year-old is 76, the start of the super senior stage. It puts the average lifespan at around 12 to 14 years, with some cats reaching their late teens or early twenties.
What is the DNA methylation formula for dog age?
Human age = 16 × ln(dog age) + 31, from Wang et al. (2020) in Cell Systems, who compared DNA methylation in 104 Labrador retrievers with human data. It ages puppies quickly, since a 1-year-old dog comes out at 31, then slows: a 7-year-old is 62 and a 12-year-old 71. It was fitted on one breed, so it is a rough guide for others.
When is a cat considered senior?
International Cat Care calls cats senior from 11 to 14 years and super senior from 15 years. The earlier stages are kitten (up to 6 months), junior (7 months to 2 years), adult (3 to 6 years) and mature (7 to 10 years). An 11-year-old cat equals about 60 human years on its chart.
What are the life stages of a dog?
The 2019 AAHA Canine Life Stage Guidelines use five: puppy, young adult, mature adult, senior and end of life. When each stage starts depends on the dog's size and breed, and the size chart shows why: a giant dog of 10 already equals 78 human years, while a small dog of the same age equals 56.
About this calculator
Sources
- AAHA / Zoetis — My pet's physiological age (cat and dog age chart, 2019)
- International Cat Care — How to tell your cat's age in human years
- Wang T. et al. (2020). Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems 11(2), 176–185
For fun. This result has no scientific basis.
Checked against references
This calculator includes 8 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.