How old is a 5 year old dog in human years?
A 5 year old dog is between 36 and 42 in human years, depending on size. A small dog comes to 36, a medium dog 37, a large dog 40 and a giant dog 42.
Size-based chart, medium dog
- Research formula (2020)
- 57
5 year old dog in human years by size
| Dog size | Human years | Next year | Roughly like |
|---|---|---|---|
| Small | 36 | +4 | a person in their mid 30s |
| Medium | 37 | +5 | a person in their late 30s |
| Large | 40 | +5 | a person in their early 40s |
| Giant | 42 | +7 | a person in their early 40s |
After the second year the size matters. Between 5 and 6 a small dog gains 4 human years and a giant dog gains 7. The 2020 research formula gives 57, above the range from the size chart.
Dog age against human age
The dots mark a 5 year old dog. Big dogs climb faster after the first two years.
Ages around 5
| Dog age | Small | Medium | Large | Giant | Research formula |
|---|---|---|---|---|---|
| 3 | 28 | 28 | 29 | 30 | 49 |
| 4 | 32 | 33 | 35 | 36 | 53 |
| 5 | 36 | 37 | 40 | 42 | 57 |
| 6 | 40 | 42 | 45 | 49 | 60 |
| 7 | 44 | 46 | 50 | 56 | 62 |
Compared with the old rule
The old rule of seven human years for each dog year would make a 5 year old dog 35. The size chart gives 36 to 42, so the old rule is 1 to 7 years too low here. Dogs age fast early on and then more slowly, and bigger dogs age faster later in life.
Questions
How old is a 5 year old small dog in human years?
About 36. Small dogs age more slowly in later years than large ones.
How old is a 5 year old large dog in human years?
About 40, and a giant dog comes to 42.
How old is a 5 year old dog if I do not know the size?
Use the size your dog will be as an adult. If you are unsure, the medium result of 37 is a fair middle guess.
What is 37 human years in dog years?
For a medium dog that is about 5 years. Try the human years to dog years calculator for any age.
Is this exact?
No. It is a general guide based on veterinary charts, and each dog ages differently. Your vet can say what the stage of life means for your dog's care.
Other dog ages
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
For any age and a size of your own, use the dog years to human years calculator. For cats see cat years to human years.
Sources
- American Animal Hospital Association (AAHA), canine and feline age chart, human-year equivalents by dog size.
- Wang T. et al., "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome", Cell Systems, 2020 (University of California San Diego).
Last reviewed 2026-10-26.