# Cat Age Calculator

> Converts a cat's age to human-equivalent years with the veterinary convention used by International Cat Care and the AAHA/AAFP chart (first year 15, second year 9, then 4 per year) and assigns the International Cat Care life stage (kitten, junior, adult, mature, senior, super senior).

- Calculator id: `cat-age` · Category: Everyday Life (`everyday`) · Tool name: `convert_cat_age_to_human_years`
- Canonical page: https://tttkmbb.com/everyday/cat-age · This document: https://tttkmbb.com/everyday/cat-age.md · JSON definition: https://tttkmbb.com/everyday/cat-age.json

## Purpose

Converts a cat's age to human-equivalent years with the veterinary convention used by International Cat Care and the AAHA/AAFP chart (first year 15, second year 9, then 4 per year) and assigns the International Cat Care life stage (kitten, junior, adult, mature, senior, super senior).

**Use when:** You want a cat's age in human years or its life stage for feeding, vaccination or health-check planning.

**Do not use when:** The animal is a dog (use dog-age, which adjusts for breed size) or you need calorie needs (use pet-calories).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `cat_age_years` | number | years | required | Age of the cat in years (e.g. 0.5 for six months). (min 0.1, max 40) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `human_years` | number | years | Human years by the 15 / 9 / 4-per-year convention (six months ≈ 10). |
| `life_stage` | string |  | International Cat Care stage: kitten (0–6 months), junior (7 months–2 years), adult (3–6), mature (7–10), senior (11–14), super senior (15+). |
| `next_stage` | string |  | The following life stage and the cat age at which it begins. |

## Formula

`age ≤ 0.5: 20·age; 0.5–1: 10 + 10·(age − 0.5); 1–2: 15 + 9·(age − 1); age > 2: 24 + 4·(age − 2)`

The convention approximates feline maturation: a 1-year-old cat is roughly a 15-year-old human and a 2-year-old about 24; after that each cat year adds about four human years. Individual cats vary with genetics, diet and indoor/outdoor life.

## Data Sources

- International Cat Care – How to tell your cat's age in human years — https://icatcare.org/advice/how-to-tell-your-cats-age-in-human-years/ (reference, retrieved 2026-09-24)
- AAHA (2019) Canine and Feline Age Chart – physiological age in human years by size class — https://www.aaha.org/wp-content/uploads/globalassets/02-guidelines/canine-life-stage-2019/canine_and_feline_age_chart_poster.pdf (standard, retrieved 2026-09-24)
- AVMA – Senior pets: how a pet's age compares with a human's — https://www.avma.org/resources-tools/pet-owners/petcare/senior-pets (reference, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/cat-age?cat_age_years=…`
- `POST https://tttkmbb.com/api/v1/calculate/cat-age` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/cat-age · OpenAPI operationId `convert_cat_age_to_human_years` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "cat-age", "inputs": {…}}`

## Example

- 5-year-old cat: inputs `{"cat_age_years":5}` → `{"human_years":36,"life_stage":"Adult","next_stage":"Mature from 7 years"}`
- 12-year-old cat: inputs `{"cat_age_years":12}` → `{"human_years":64,"life_stage":"Senior","next_stage":"Super senior from 15 years"}`

```
GET https://tttkmbb.com/api/v1/calculate/cat-age?cat_age_years=5
```

## Limitations

The animal is a dog (use dog-age, which adjusts for breed size) or you need calorie needs (use pet-calories). The convention approximates feline maturation: a 1-year-old cat is roughly a 15-year-old human and a 2-year-old about 24; after that each cat year adds about four human years. Individual cats vary with genetics, diet and indoor/outdoor life. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**When is a cat considered senior?**

International Cat Care uses 11 years (super senior from 15); the AAHA/AAFP guidelines start the senior stage at 10. Many vets recommend twice-yearly check-ups from about 10 years.

**Do indoor and outdoor cats age differently?**

The conversion is the same, but outdoor cats face more injury and disease, so their life expectancy is shorter on average.

## Related

- [Dog Age Calculator](https://tttkmbb.com/everyday/dog-age.md) — Same conversion for dogs, adjusted for size.
- [Pet Calorie Calculator](https://tttkmbb.com/everyday/pet-calories.md) — Daily calorie needs for cats by weight and life stage.