The conversion. The first cat year is roughly 15 human years, the second adds about 9 (24 at age two), and each year after that adds about 4. So a 10-year-old cat is around 56 and a 20-year-old around 96. Charts differ by a year or two — treat it as a rough translation, not a biological measurement.
The life stages (2021 AAHA/AAFP Feline Life Stage Guidelines). Kitten: birth to 1 year · young adult: 1–6 years · mature adult: 7–10 years · senior: over 10 years, plus an end-of-life stage that can come at any age. The guidelines call for at least an annual examination for every cat, and at least every six months for senior cats.
Human-years table. 1 → 15 · 2 → 24 · 3 → 28 · 4 → 32 · 5 → 36 · 6 → 40 · 7 → 44 · 8 → 48 · 9 → 52 · 10 → 56 · 11 → 60 · 12 → 64 · 13 → 68 · 14 → 72 · 15 → 76 · 16 → 80 · 17 → 84 · 18 → 88 · 19 → 92 · 20 → 96.
Kitten milestones in the UK. First core vaccination at 8–9 weeks and the second at 12 weeks (a third at 16 weeks in some risk areas), neutering commonly from 4 months, and — in England, since 10 June 2024 — every pet cat must be microchipped and registered before it is 20 weeks old, with a fine of up to £500 for owners who do not comply within 21 days. The socialisation window closes at about 9 weeks, which is why early, gentle handling matters so much.
What vets watch as cats age. From about 7: kidney disease, hyperthyroidism, high blood pressure, dental disease and arthritis — all common, all quiet at the start, which is why baseline bloods, urine and a blood-pressure check are worth asking for. Senior cats often hide weight loss under a thicker coat: weigh at home monthly and compare.
Sources. 2021 AAHA/AAFP Feline Life Stage Guidelines (Quimby et al.) · ISFM/AAFP environmental and life-stage guidance · UK compulsory microchipping regulations for cats in England (10 June 2024). Checked 4 October 2026. — Information only, not veterinary advice.