以下详细说明暂以英文提供。
The rule behind the conversion
The old "multiply by seven" saying hides how unevenly pets age. Vets commonly use a front-loaded curve: a dog or cat's first year of life builds the equivalent of about 15 human years, the second adds another 9, and every later year adds a steady 4–6 depending on the animal. Size matters for dogs because big breeds age faster and live shorter — a Great Dane is senior years before a Chihuahua — so the yearly increment runs 4 for small dogs, 5 for medium, 6 for large, and 4 for cats of any size.
Life stages, from kitten to geriatric
Pets move through recognizable chapters: the kitten or puppy year of chaotic growth, the junior teenage phase around one to two, a long prime in the middle, then the senior years, and finally geriatric care with twice-yearly vet checks. The labels here follow common veterinary guidance — prime roughly years three to six, senior seven to ten, geriatric from eleven — though large dogs reach each milestone sooner than small ones. Matching food, exercise, and screening to the right stage does more for a pet than any conversion table.
中国本地参考
日常计算时值得知道的中国本地规则：
- 计量的单位习惯: 住房面积用平方米，土地常用亩（1 亩 ≈ 666.7 平方米）；里程用公里，油耗用 L/100km。
- 日期与数字格式: 日期写作 2026年10月13日（年-月-日）；大数习惯用万、亿（1 万 = 10,000，1 亿 = 100,000,000）。
- 法定节假日: 全年法定节假日 11 天，春节与国庆为长假；调休安排每年由国务院办公厅发布。
- 速度与限速: 高速公路最高限速 120 km/h，城市快速路多为 80 km/h，均以公里每小时计。
- 鞋服尺码: 鞋码用中国码（毫米制），服装常用 155/80A 这类身高围度组合，与欧美码不同。
数据核对：2026 年 10 月
常见问题
Is the "multiply by seven" rule wrong?
Very. A one-year-old cat can reproduce and is finished growing, which no seven-year-old human is. The front-loaded curve — 15 human years in year one, 9 more in year two, then 4–6 per year — tracks development and breed lifespans far better.
Why do large dogs age faster?
Nobody has fully explained it, but across breeds bigger bodies run through their repair budget quicker: Great Danes live around 8–10 years while small breeds often reach 15 or more. The extra human years per birthday reflect that gap.
How accurate is the result for a mixed-breed pet?
Treat it as a fun estimate. Mixed-breed dogs span the size range, and individual health, weight, and genetics shift aging by years in either direction. For medical decisions, your vet reads age alongside bloodwork and body condition, not a formula.