Dog & Cat Age Calculator (Human Years)
＋More features: reverse conversion (human → pet) and an age reference table
Reverse conversion: how old is a human in pet years?
Answers “my age would be about how many pet years?”
Age reference table for 1–20 years
Shows what human age a pet aged 1–20 corresponds to (the same formula applies to cats and small/medium dogs).
Just enter your cat’s or dog’s age to instantly see roughly how old they would be in human years (for cats and small-to-medium dogs). It also shows when the senior stage typically begins. Useful when thinking about checkups or when to switch to senior food.
How to use
- Choose cat or dog (small or medium).
- Enter your pet’s age (0.5 for 6 months old).
- The moment you type, the approximate human age and life stage appear automatically.
How it is calculated
- 1 pet year = about 15 human years / 2 years = about 24 / then about +4 human years per year
- The idea is that pets grow to the equivalent of a 24-year-old human within their first two years, then age more slowly — a guideline formula introduced by Western veterinary organizations.
- Example: a 5-year-old cat → 24 + 4×3 = about 36 human years
- The old rule of thumb “human age = pet age × 7” does not fit the fast growth of the early years, so this formula is now the mainstream guideline.
Sources and assumptions
- The formula is a guideline widely used by veterinary organizations in the West (for example, the life-stage guidelines of the American Animal Hospital Association (AAHA), in English). It is a rough guide, not a scientifically exact conversion.
Assumptions and notes
- Large dogs (roughly 25 kg and over) age faster, and this formula does not apply to them (large dogs are considered senior at around 7–8 years).
- Actual aging varies a lot with breed, environment and the individual animal. For health care, consult your veterinarian.
Frequently asked questions
Is “1 dog year = 7 human years” wrong?
It is an oversimplification. Dogs and cats race past the equivalent of a 20-year-old human in their first one to two years, so ×7 does not fit early life. The formula used here — fast at first, slower afterwards — is considered a closer guideline to reality.
From what age is a pet senior?
Cats and small-to-medium dogs enter their mid-40s in human terms at around age 7. From age 7 it is often recommended to move from one checkup a year to two.
How long do cats live?
The average lifespan of indoor-only cats is reported to be around 16 years. Cats living past 20 (about 96 human years) are no longer rare.