Dog & Cat Age Calculator
Enter your pet's age to see the equivalent in human years, using up-to-date veterinary formulas rather than the old "multiply by 7" rule.
Dog & Cat Years to Human Years Chart
A quick reference if you don't want to enter numbers above — human-year equivalents for common pet ages, broken out by dog size (cats use one curve regardless of breed).
| Pet age | Small dog | Medium dog | Large dog | Giant dog | Cat |
|---|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 31 | 28 |
| 4 | 32 | 34 | 36 | 38 | 32 |
| 5 | 36 | 39 | 42 | 45 | 36 |
| 6 | 40 | 44 | 48 | 52 | 40 |
| 7 | 44 | 49 | 54 | 59 | 44 |
| 8 | 48 | 54 | 60 | 66 | 48 |
| 9 | 52 | 59 | 66 | 73 | 52 |
| 10 | 56 | 64 | 72 | 80 | 56 |
| 11 | 60 | 69 | 78 | 87 | 60 |
| 12 | 64 | 74 | 84 | 94 | 64 |
| 13 | 68 | 79 | 90 | 101 | 68 |
| 14 | 72 | 84 | 96 | 108 | 72 |
| 15 | 76 | 89 | 102 | 115 | 76 |
| 16 | 80 | 94 | 108 | 122 | 80 |
| 18 | 88 | 104 | 120 | 136 | 88 |
| 20 | 96 | 114 | 132 | 150 | 96 |
How the conversion works
Both curves follow the same shape: a dog or cat's first year of life is treated as roughly 15 human years — most of a puppy or kitten's physical and social development happens in that first year. The second year adds about 9 more human years (bringing a 2-year-old pet to about 24). After that, aging slows and becomes steady: each additional year adds a fixed number of human years depending on size — 4 for small dogs and all cats, 5 for medium dogs, 6 for large dogs, and 7 for giant breeds, reflecting how larger dogs tend to age faster in their later years and have shorter lifespans than smaller ones.
FAQ
Why isn't it just 'multiply by 7'?
The old ×7 rule doesn't reflect how animals actually age — dogs and cats mature much faster in their first couple of years than the multiplier suggests, then age more slowly afterward. Modern estimates use a curve rather than a flat multiplier.
Does dog size really affect aging speed?
Yes — larger dog breeds tend to have shorter lifespans and age faster in their later years compared to smaller breeds, which is why this calculator factors in size for dogs.
Is this calculation exact?
No single formula perfectly matches every individual animal — breed, genetics, and health all play a role. This gives a reasonable estimate based on commonly used veterinary aging curves, not a precise medical measurement.
Do cats age differently by breed or size the way dogs do?
Size and breed have much less impact on cat aging compared to dogs, so this calculator uses a single formula for all cats rather than breaking it down by size.
How many human years is 5 dog years?
A 5-year-old dog is roughly 36–45 in human years, depending on size: about 36 for a small dog, 39 for medium, 42 for large, and 45 for a giant breed. Enter your dog's exact size above for a precise figure.
How old is an 8-year-old dog in human years?
An 8-year-old dog is about 48–66 in human years: roughly 48 for a small dog, 54 for medium, 60 for large, and 66 for a giant breed.
What is 15 in dog years?
If you mean a dog that's lived 15 years, that's about 76–115 in human years depending on size (76 small, 89 medium, 102 large, 115 giant). If you mean converting a human age of 15 into dog years, this calculator works in the other direction — enter the pet's age in years, not the human age.
How old is a 10-year-old cat in human years?
A 10-year-old cat is about 56 in human years, using the same steady curve as a small dog.
About this tool
This calculator converts your dog's or cat's age into an equivalent human age, using aging-curve estimates rather than the outdated 'multiply by 7' rule. Dog results also factor in size, since larger breeds age differently than smaller ones. This is a general estimate, not veterinary advice.