Cat Age Calculator
Convert your cat’s age into human years and see the life stage they are in.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This approximate conversion follows the commonly used feline age chart: about 10 human years at six months, 15 at one year, 24 at two years and roughly four more per cat year after that. The age bands follow AAHA/AAFP life-stage ranges; individual development varies, so this is not a health or lifespan prediction. Choose years and months or a birth date and reference date. Both inputs use the same approximate age-equivalence curve; this is not a health assessment.
Worked example
calculated with the default values below
Age input Years and months · Cat age 5 years · Extra months 0 months · Birth date 2018-05-01 · Calculate age on 2026-10-31 Human years equivalent 36.0 years · Life stage Young adult cat · Cat age 5.00 years
General background references
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
H = 15a (a ≤ 1); H = 15 + 9(a − 1) (1 < a ≤ 2); H = 24 + 4(a − 2) (a > 2)
- H
- Equivalent human years
- a
- Cat age in years
a includes cat months divided by 12; year 1 = 15, year 2 adds 9, later years add 4.
Frequently asked questions
How is a cat’s human-age equivalent estimated?
This approximate chart maps six months to about 10 human years, one year to 15, two years to 24, then adds roughly four per cat year. The life-stage labels follow AAHA/AAFP age bands: kitten under 1, young adult 1–6, mature adult 7–10 and senior over 10. These are broad reference ranges, not a diagnosis or lifespan estimate.