This calculator converts feline chronological age into equivalent human years using American Animal Hospital Association (AAHA) life stage guidelines, adjusted for environmental exposure and lifestyle factors. While basic aging formulas assume a protected indoor environment, cats with unsupervised outdoor access experience higher physiological wear, infectious disease risks, and environmental stressors.

### Calculation Mechanics & Lifestyle Factors The tool applies the standard AAHA biological development curve with an environmental wear adjustment:

- **Baseline Development Curve:** - First Year: Feline age 0 to 1 equals $15 \times \text{Cat Age}$ human years. - Second Year: Feline age 1 to 2 equals $15 + (\text{Cat Age} - 1) \times 9$ human years (reaching 24 human years at age 2). - Third Year and Beyond: Each subsequent calendar year adds 4 human years ($24 + (\text{Cat Age} - 2) \times 4$). - **Lifestyle Adjustment Factor:** - Strictly Indoor: Standard baseline ($0\text{ extra years}$). - Indoor / Outdoor Access: Standard baseline with moderate risk exposure. - Strictly Outdoor: For outdoor cats older than 3 years, the tool adds an extra $1.5\text{ human years}$ per calendar year to reflect accelerated cellular and organ strain: $ ext{Human Age} = 24 + (\text{Cat Age} - 2) \times 4 + (\text{Cat Age} - 3) \times 1.5$

### Worked Numeric Example For a 5-year-old strictly outdoor cat: 1. Baseline calculation: $24 + (5 - 2) \times 4 = 24 + 12 = 36\text{ human years}$. 2. Outdoor lifestyle adjustment: $(5 - 3) \times 1.5 = 2 \times 1.5 = 3.0\text{ human years}$. 3. Total adjusted age: $36 + 3 = 39\text{ human years}$. 4. Assigned AAHA cohort: 'Young Adult'.

### Client-Side Execution Note All conversions, lifestyle multipliers, and metric lookups compute client-side in your web browser. No inputs or health queries are stored or transmitted.