If a dog is 9 years old, how many human years is that? - briefly
If a dog is 9 years old, it is roughly equivalent to being 56 in human years, according to a commonly accepted formula. This conversion rate accounts for the faster aging process of dogs compared to humans.
If a dog is 9 years old, how many human years is that? - in detail
The equivalence between dog and human years is a subject of ongoing scientific debate, but several widely accepted formulas can help estimate a dog's age in human terms. One of the most recognized methods is the "7-year rule," which suggests that for every year that passes, a dog ages approximately seven human years. However, this formula oversimplifies the aging process and does not account for differences between breeds and sizes.
A more nuanced approach was developed by veterinarian Dr. William Fortney, who proposed the following formula:
- For the first year of a dog's life: 1 human year = 1 dog year.
- For the second year: 4 dog years.
- Each subsequent year adds approximately 5 dog years (e.g., 3rd year = 9, 4th year = 14).
Using this formula for a 9-year-old dog: 1st year: 1 human year 2nd year: +4 dog years Years 3 to 9: 5 dog years per year x 7 years = 35 dog years Total: 1 (1st year) + 4 (2nd year) + 35 (years 3-9) = 40 human years.
Another method, proposed by Dr. Kara M. Burns and Mark Mitchell, considers the size of the dog. According to their formula:
- Small dogs (under 20 lbs): 16 human years for the first year, then 11 additional years per subsequent year.
- Medium dogs (20-50 lbs): 13 human years for the first year, then 9 additional years per subsequent year.
- Large dogs (50-100 lbs) and giant breeds (over 100 lbs): 10 human years for the first year, then 7 or 5 additional years per subsequent year, respectively.
For a small dog that is 9 years old: 1st year: 16 human years 2nd to 9th years: 8 years x 11 = 88 human years Total: 16 (1st year) + 88 (years 2-9) = 104 human years.
For a medium dog that is 9 years old: 1st year: 13 human years 2nd to 9th years: 8 years x 9 = 72 human years Total: 13 (1st year) + 72 (years 2-9) = 85 human years.
For a large dog that is 9 years old: 1st year: 10 human years 2nd to 9th years: 8 years x 7 = 56 human years Total: 10 (1st year) + 56 (years 2-9) = 66 human years.
For a giant breed dog that is 9 years old: 1st year: 10 human years 2nd to 9th years: 8 years x 5 = 40 human years Total: 10 (1st year) + 40 (years 2-9) = 50 human years.
In conclusion, determining the human equivalent of a dog's age depends on the formula used and the size of the dog. The range can vary significantly, from approximately 60 to over 100 human years for a 9-year-old dog.