Dog Age Calculator
Quick answer. Human age ≈ 16 × ln(dog age in years) + 31, from the 2020 UC San Diego epigenetic study. The ×7 rule is wrong. AVMA's size bands say when a small, medium, large or giant dog is usually considered senior.
Why the ×7 rule is wrong
The AVMA states it directly: contrary to popular belief, dogs do not age at a rate of 7 human years per dog year. A 1-year-old dog has already done a lot of growing up. Multiplying by 7 calls that dog a 7-year-old child. The epigenetic formula below calls the same dog about 31, because 16 × ln(1) + 31 is 31. A 2-year-old dog is about 42 on the formula, and 14 if you multiply by 7.
Size breaks the rule a second time. The AVMA says larger dogs tend to have shorter lives, and it publishes different ages for when a small, medium, large or giant dog is usually considered senior. One number for every breed cannot survive that.
The epigenetic formula
In 2020, Wang, Ideker and colleagues, including a group at UC San Diego, compared DNA methylation in dogs and humans. The dogs were 104 Labrador retrievers, over a 16-year age range, set against methylation patterns from 320 people. The relationship they published is not a straight line. Combining the two directions of the comparison, they give one function:
human age = 16 × ln(dog age) + 31
Ln is the natural logarithm, and dog age is in years. NHGRI's write-up of the same work says the formula lines up with shared milestones: eight weeks in dogs with about nine months in human infancy, and a 12-year Labrador lifespan with about 70 human years. The calculator applies the formula to the age you type. Twelve years comes out at about 70.8. Eight weeks is about 0.15 years, and the logarithm is steep there, so a fraction of a year is a rough figure. NHGRI's "about nine months" is their milestone reading of that early stretch.
Because the sample was all Labrador retrievers, the formula is not a size adjustment. A Great Dane and a Chihuahua of the same age get the same epigenetic number. The AVMA bands beside it are what changes with size.
The AVMA size bands
The AVMA does not publish one human-year birthday chart for every size. On its senior-pet page it publishes when dogs are usually considered senior, from AKC lifespan data, in four bands. Its separate poster, "Pets age faster than people", is a human-year scale for a medium dog of 21 to 50 lb, and the poster says the figures are approximate and that weight and breed also influence aging. This page uses the four bands the AVMA states in words. It does not copy a year-by-year table onto those bands.
| Size | Adult weight | Usually considered senior from about |
|---|---|---|
| Small or toy | Less than 20 lb (about 9 kg) | 8 to 11 years |
| Medium | 20 to 50 lb (about 9 to 23 kg) | 8 to 10 years |
| Large | 50 to 90 lb (about 23 to 41 kg) | 8 to 9 years |
| Giant | More than 90 lb (about 41 kg) | 6 to 7 years |
Kilograms here are a conversion of the AVMA's pounds, for readers who weigh dogs in kilos. The AVMA states the bands in pounds. Use the adult weight you expect, not a puppy's current weight, when you pick a row.
Dog age calculator
Enter an age in years and a size. The result is the epigenetic estimate, the ×7 figure next to it so you can see the gap, and the AVMA senior band for that size. The tables under the form are the same information with JavaScript turned off.
Epigenetic ages without the form
These figures are 16 × ln(dog age) + 31, rounded to one decimal. The ×7 column is the old rule, shown so the difference is visible. Ages past 16 years are outside the methylome sample.
| Dog's age (years) | Epigenetic human age | ×7 rule |
|---|---|---|
| 1 | 31 | 7 |
| 2 | 42.1 | 14 |
| 3 | 48.6 | 21 |
| 4 | 53.2 | 28 |
| 5 | 56.8 | 35 |
| 6 | 59.7 | 42 |
| 7 | 62.1 | 49 |
| 8 | 64.3 | 56 |
| 10 | 67.8 | 70 |
| 12 | 70.8 | 84 |
| 14 | 73.2 | 98 |
| 16 | 75.4 | 112 |
Track the years you can actually measure
A human-year number does not book the next vet visit. PupPlan keeps weight, feeding and care reminders as a dog moves into the senior band your vet recognises.
How to read the result
Use the epigenetic number as a translation of one published clock, and the AVMA band as the point where senior care usually starts for that size. Neither number diagnoses arthritis, kidney disease or cognitive change. A dog can need a senior plan before the band, or stay brisk past it. The senior dog guide covers what to watch for, and the feeding guide covers how portions change with age.
Tip: If you only remember two checks, remember these. The ×7 rule underestimates the first two years. Giant dogs are usually treated as senior several years before small dogs.
Frequently Asked Questions
Why is multiplying a dog's age by 7 wrong?
The AVMA says dogs do not age at a rate of 7 human years for each dog year. The first year of a dog's life covers growing up that a 7-year-old child has not done, and a large dog is usually considered senior sooner than a small dog. One multiplier cannot describe both.
What formula does this calculator use?
Human age = 16 × ln(dog age in years) + 31. That is the function Wang and colleagues published in Cell Systems in 2020, from work at UC San Diego and collaborators. The dogs in the methylome sample were 104 Labrador retrievers, over a 16-year age range.
When is a dog senior?
The AVMA gives ranges by size, using AKC lifespan data: about 8 to 11 years for a small or toy dog under 20 lb, 8 to 10 years for a medium dog of 20 to 50 lb, 8 to 9 years for a large dog of 50 to 90 lb, and 6 to 7 years for a giant dog over 90 lb. The individual dog still needs a vet's eye.
Sources
This guide follows published guidance from the organisations named below. Your own vet knows this dog; use these pages as background, not as a diagnosis or a timetable.