Growth and age
Dog years to human years: age chart by size
Using the formula from a 2020 DNA study, a 1-year-old dog compares with about 31 human years, a 2-year-old with 42 and a 10-year-old with 68. The study was mainly of Labrador retrievers, so treat these as rough comparisons. Size does not change the formula, but bigger dogs reach their senior years sooner.
Dog age chart by size
The chart gives the human-year estimate from PupCalendar's Dog Age Calculator for each whole year from 1 to 16. The formula has no size setting, so the human-year column is the same for every dog.
The size columns show where each age sits against the senior ages the AVMA gives by size. The AVMA counts a dog as senior in the last quarter of its breed's expected lifespan, which comes sooner for bigger dogs.
| Dog age | Human years (all sizes) | Small, under 20 lb (9 kg) | Medium, 20 to 50 lb (9 to 23 kg) | Large, 50 to 90 lb (23 to 41 kg) | Giant, over 90 lb (41 kg) |
|---|---|---|---|---|---|
| 1 year | 31 | Not yet | Not yet | Not yet | Not yet |
| 2 years | 42 | Not yet | Not yet | Not yet | Not yet |
| 3 years | 49 | Not yet | Not yet | Not yet | Not yet |
| 4 years | 53 | Not yet | Not yet | Not yet | Not yet |
| 5 years | 57 | Not yet | Not yet | Not yet | Not yet |
| 6 years | 60 | Not yet | Not yet | Not yet | May be senior |
| 7 years | 62 | Not yet | Not yet | Not yet | May be senior |
| 8 years | 64 | May be senior | May be senior | May be senior | Senior |
| 9 years | 66 | May be senior | May be senior | May be senior | Senior |
| 10 years | 68 | May be senior | May be senior | Senior | Senior |
| 11 years | 69 | May be senior | Senior | Senior | Senior |
| 12 years | 71 | Senior | Senior | Senior | Senior |
| 13 years | 72 | Senior | Senior | Senior | Senior |
| 14 years | 73 | Senior | Senior | Senior | Senior |
| 15 years | 74 | Senior | Senior | Senior | Senior |
| 16 years | 75 | Senior | Senior | Senior | Senior |
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)AVMA: Caring for senior cats and dogs (opens in a new tab)
One dog year is how many human years?
By the formula, a dog's first year compares with about 31 human years, because the natural log of 1 is zero. The second year adds about 11 more, and later years add less and less. UC Davis notes that dogs age much faster than people in their first years, which is why the early years count for so much.
Another common guide, described by UC Davis, counts a medium-sized dog's first year as 15 human years. The two methods are built in different ways, so they give different numbers. Both are rough comparisons.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)
Is one dog year really 7 human years?
No. The AVMA states that dogs do not age at 7 human years per dog year. UC Davis explains that the rule probably came from average lifespans of about 10 years for dogs and 70 for people, and that it misses how fast dogs grow up.
By the 7-year rule a 1-year-old dog would be 7 in human years. The formula gives 31, which reflects how much a dog matures in its first year.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)AVMA: Caring for senior cats and dogs (opens in a new tab)
How do I convert human years to dog years?
Run the formula backwards: take the human age, subtract 31, divide by 16, then raise e to that power. This only works from 31 human years upward, because the formula starts at a 1-year-old dog.
For example, 50 human years matches about 3.3 dog years, 60 about 6.1 and 70 about 11.4. The calculator converts dog years to human years, so read across the chart to go the other way.
Sources: UC Davis School of Veterinary Medicine: calculating your dog's age (opens in a new tab)
How do I find my dog's age in human years?
Enter your dog's age in the Dog Age Calculator, from 1 to 20 years with up to one decimal place. A 10-year-old dog gives 16 x ln(10) + 31, about 67.8, which rounds to 68 human years.
Worked example
Dog age 10 years
- Formula
- 16 x ln(10) + 31
- Rounded comparison
- 68 human years
- Senior stage by AVMA size range
- Small or medium: may be senior; large or giant: senior
Checked against the Dog Age Calculator. A rough comparison from one study, not a clinical age assessment.
Ages above 16 go beyond the oldest dogs in the study, so the calculator marks them as an extrapolation. Use the result as a prompt to talk about senior care with your vet, not as a health check.
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.
How do I calculate dog years to human years?
Multiply the natural log of your dog's age in years by 16 and add 31. The Dog Age Calculator does this for ages 1 to 20 and rounds the result.
One dog year is how many human years?
About 31 by the formula used here. Another common guide says 15 for a medium-sized dog. Both are rough comparisons, not exact ages.
Is there a human years to dog years calculator?
Our calculator converts dog years to human years. To go the other way, read across the chart or run the formula backwards.
Do small dogs age slower than large dogs?
Small dogs tend to live longer than large dogs, and the AVMA gives later senior ages for smaller breeds. The formula itself has no size setting.
How old is a 10 year old dog in human years?
About 68 by the formula. By the AVMA size ranges, a 10-year-old large or giant dog is senior, and a small or medium dog may be.
Can the result predict lifespan?
No. It is a rough comparison from a study of mainly Labrador retrievers, not a health or lifespan estimate.
Sources and checked dates
Each note explains what its source supports. Open the link to read the guidance yourself.
Gives the equation human age = 16 ln(dog age) + 31 from a DNA methylation study of 104 Labrador retrievers aged 4 weeks to 16 years. Explains that multiplying by 7 is not accurate because dogs age fastest early on, that breeds age differently and small dogs tend to live longer than large dogs, and describes a separate guide of 15 human years for a medium-sized dog's first year.
States that dogs do not age at 7 human years per dog year. Dogs are considered senior in the last 25 percent of their breed's expected lifespan: small or toy breeds under 20 pounds at 8 to 11 years, medium breeds of 20 to 50 pounds at 8 to 10, large breeds of 50 to 90 pounds at 8 to 9, and giant breeds over 90 pounds at 6 to 7.