# Cat Age Calculator

A cat's age in human years is a published convention, not a measurement. International Cat Care puts a two-year-old cat at 24 human years; the Cornell Feline Health Center puts it at 21. Both then add 4 human years per cat year after that, so the two stay exactly 3 human years apart for the rest of the cat's life. This calculator uses the International Cat Care table (a one-year-old cat is about 15) and shows the Cornell figure beside it. International Cat Care's table stops at 25 years — beyond that age, the figure holds steady rather than extending a curve the source doesn't support.

| Cat age | Human years |
|---|---|
| 1 month | 1 |
| 2 months | 2 |
| 3 months | 4 |
| 4 months | 6 |
| 5 months | 8 |
| 6 months | 10 |
| 7 months | 12 |
| 12 months | 15 |
| 18 months | 21 |
| 24 months | 24 |

## Common questions

### How old is my cat in human years?

A one-year-old cat is about 15 in human years, and a two-year-old about 24. After that, International Cat Care adds 4 human years for every cat year — so a ten-year-old cat is about 56.

### Why do different websites give different answers?

Because there is no single published conversion. International Cat Care puts a two-year-old cat at 24 human years; the Cornell Feline Health Center puts it at 21. Both then add 4 years per year, so the two stay exactly 3 human years apart for the rest of the cat's life. This calculator uses the International Cat Care table and shows you the Cornell figure beside it.

### Is the “multiply by seven” rule true for cats?

No. It would make a one-year-old cat seven in human years, where both published tables put it near 15. Cats do most of their growing up in the first two years, and far less in each year after.

### Is this a measurement?

No, and that matters. These numbers are a convention agreed by veterinary organisations to describe life stages, not a measurement of biological age. That is why two respected sources can differ by 3 human years and neither is wrong.

### How old is a kitten in human years?

International Cat Care publishes the first year month by month: a 4-month-old kitten is about 6 in human years, and a 6-month-old about 10. That is why a kitten can behave like a small child one month and a teenager the next.

## Sources

- Wikidata — dog breed mass (property P2067) — Wikimedia Foundation, query run 2026-07-22, CC0 license (https://query.wikidata.org/)
- Wikidata — cat breed mass (property P2067) — Wikimedia Foundation, query run 2026-07-28, CC0 license (https://query.wikidata.org/)
- Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome — Wang et al., Cell Systems, 2020, vol. 11, no. 2, p. 176–185.e6 (DNA methylation in 104 Labradors) (https://doi.org/10.1016/j.cels.2020.06.006)
- Body-Weight Changes during Growth in Puppies of Different Breeds — Hawthorne et al., Journal of Nutrition, 2004, vol. 134, p. 2027S (https://doi.org/10.1093/jn/134.8.2027S)
- Management of Reproduction — gestation period in the bitch — Merck Veterinary Manual, “Approximate Gestation Periods” table, accessed 2026-07-23 (https://www.merckvetmanual.com/multimedia/table/approximate-gestation-periods)
- Dystocia in Small Animals — Merck Veterinary Manual, “Diagnosis of Dystocia in Small Animals” section, accessed 2026-07-28 (https://www.merckvetmanual.com/reproductive-system/reproductive-diseases-of-the-female-small-animal/dystocia-in-small-animals)
- Factors affecting gestation duration in the bitch — Eilts et al., Theriogenology, 2005, vol. 64, no. 2, p. 242–251 (https://pubmed.ncbi.nlm.nih.gov/15955350/)
- Nutritional Requirements of Small Animals — energy requirements of the dog and cat — Merck Veterinary Manual, “Energy” section, accessed 2026-07-23 (https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals)
- Chocolate Toxicosis in Animals — Merck Veterinary Manual, “Methylxanthine Content of Various Types of Chocolate” table and “Etiology” section, accessed 2026-07-28 (https://www.merckvetmanual.com/toxicology/food-hazards/chocolate-toxicosis-in-animals)
- ASPCA Poison Control — ASPCA, 24-hour emergency line, accessed 2026-07-28 (https://www.aspca.org/pet-care/aspca-poison-control)
- How old is your cat? — life stage and human equivalent age — International Cat Care (Cat Friendly Clinic), accessed 2026-07-28 (https://icatcare.org/resources/cat-friendly-clinic/how-old-is-your-cat-handout.pdf)
- The Special Needs of the Senior Cat — cat age in human years — Cornell Feline Health Center, Cornell University, accessed 2026-07-28 (golden-test source, not used to build the calculation) (https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/special-needs-senior-cat)
- Calorie Needs for an Average Healthy Adult Cat in Ideal Body Condition — WSAVA Global Nutrition Committee, updated July 2020 (golden-test source, not used to build the calculation) (https://wsava.org/wp-content/uploads/2020/07/Calorie-Needs-for-Healthy-Adult-Cats-updated-July-2020.pdf)
- Assessment of body weight for age determination in kittens — DiGangi et al., Journal of Feline Medicine and Surgery, 2019 (tables 1 and 2, weight-for-age, male and female) (https://doi.org/10.1177/1098612X19844846)
- Kitten Age & Weight Chart — ASPCA Pro, 2023 (golden-test source, not used to build the calculation) (https://www.aspcapro.org/sites/default/files/2023-08/aspca_kittenchart_2023.pdf)

Full method: https://caninecalculators.com/sources

_Verified 2026-07-28. Estimates only — this does not replace veterinary advice._