Cat Age Calculator
Your cat's age in human years.
Quick answer
- Formula: Year 1 ≈ 15 human years; year 2 ≈ +9; then +4 per year
- Worked example — Equivalent human years (guideline): 36.0 (full example below).
Cat Age Calculator
| Equivalent human years (guideline) | 36.0 |
| Life stage | Prime |
A 5-year-old cat is about 36 in human years: 15 + 9 for the first two years, then 4 per year for three more — the Prime life stage.
Cats mature quickly at first and then age steadily. This calculator follows the commonly published guideline: about 15 human years for a cat's first year, 9 more for the second, then about 4 human years for each additional year.
It is a guideline, not exact science — indoor cats typically live longer than outdoor cats, and breed and health matter. Your veterinarian can stage your cat's life more precisely.
The formula
Worked example
A 5-year-old cat is about 36 in human years: 15 + 9 for the first two years, then 4 per year for three more — the Prime life stage.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
When is a cat considered a senior?
Most guidelines class cats as senior from about 11 years old (roughly 60 in human years on this scale), with twice-yearly vet checks commonly recommended from that age.
Do indoor and outdoor cats age differently?
The conversion table is the same, but outdoor cats face more risks and typically have shorter lifespans, so two cats of the same age can be in quite different health.
Category: Everyday Life calculators
Sources & methodology
This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.
Content last reviewed by CalcHub Editorial.
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