# Ski Length Calculator

> Recommends an alpine ski length range from skier height, adjusted for ability (beginner 10–15 cm below height, intermediate 5–10 cm, advanced 0–5 cm), ski type (powder/freeride +5 cm, carving and park −5 cm) and body weight (over 90 kg +5 cm, under 60 kg −5 cm), following the logic of retailer size charts.

- Calculator id: `ski-length` · Category: Sports & Fitness (`fitness`) · Tool name: `recommend_ski_length`
- Canonical page: https://tttkmbb.com/fitness/ski-length · This document: https://tttkmbb.com/fitness/ski-length.md · JSON definition: https://tttkmbb.com/fitness/ski-length.json

## Purpose

Recommends an alpine ski length range from skier height, adjusted for ability (beginner 10–15 cm below height, intermediate 5–10 cm, advanced 0–5 cm), ski type (powder/freeride +5 cm, carving and park −5 cm) and body weight (over 90 kg +5 cm, under 60 kg −5 cm), following the logic of retailer size charts.

**Use when:** Someone is buying or renting alpine skis and needs a length range or a single recommended length for their height, ability and ski type.

**Do not use when:** You are sizing cross-country skis (sized by weight and technique), snowboards or children's skis, or the manufacturer publishes model-specific sizing (rocker profile, waist width and turn radius change the ideal length).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `height_cm` | number | cm | required | Skier height in centimetres. (min 100, max 230) |
| `weight_kg` | number | kg | optional | Optional body weight: above 90 kg adds 5 cm, below 60 kg subtracts 5 cm. (min 20, max 200) |
| `skill` | enum: beginner \| intermediate \| advanced |  | required | Ability level; shorter skis turn more easily, longer skis are more stable at speed. |
| `ski_type` | enum: all_mountain \| carving_piste \| powder_freeride \| park_freestyle \| touring |  | optional, default "all_mountain" | Intended use; wide powder skis run longer, carving and park skis shorter. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `length_min_cm` | number | cm | Lower end of the recommended range. |
| `length_max_cm` | number | cm | Upper end of the recommended range. |
| `recommended_cm` | number | cm | Midpoint of the range rounded to the nearest centimetre; pick the closest length the model is made in. |
| `length_range_text` | string |  | The range as text, e.g. '165–170 cm'. |
| `adjustment_cm` | number | cm | Sum of the ski-type and weight adjustments applied to the ability range. |
| `notes` | string |  | Which base range and adjustments were applied. |

## Formula

`base range = height_cm + [−15, −10] (beginner), [−10, −5] (intermediate) or [−5, 0] (advanced); adjustment = +5 (powder_freeride) | −5 (carving_piste, park_freestyle) | 0 (all_mountain, touring), plus +5 if weight_kg > 90 or −5 if weight_kg < 60; length_min/max = base + adjustment; recommended_cm = round((length_min + length_max) / 2)`

Follows the height-based sizing used by retailer charts: a beginner's ski reaches roughly the chin, an expert's the top of the head. Rockered and wide powder skis ski shorter than their length, so charts push them longer; twin-tips and carving skis are ridden shorter. Heavier skiers need more ski for stability, lighter skiers less.

## Data Sources

- evo – Ski Size Chart & Calculator: how to choose ski length — https://www.evo.com/guides/how-to-choose-skis-size-chart (reference, retrieved 2026-09-24)
- Wikipedia – Ski (alpine ski types and geometry) — https://en.wikipedia.org/wiki/Ski (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/ski-length?height_cm=…&skill=…`
- `POST https://tttkmbb.com/api/v1/calculate/ski-length` 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/ski-length · OpenAPI operationId `recommend_ski_length` 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": "ski-length", "inputs": {…}}`

## Example

- 175 cm, intermediate, all-mountain, 75 kg: inputs `{"height_cm":175,"weight_kg":75,"skill":"intermediate","ski_type":"all_mountain"}` → `{"length_min_cm":165,"length_max_cm":170,"recommended_cm":168,"length_range_text":"165–170 cm","adjustment_cm":0}`
- 180 cm, beginner, powder ski: inputs `{"height_cm":180,"skill":"beginner","ski_type":"powder_freeride"}` → `{"length_min_cm":170,"length_max_cm":175,"recommended_cm":173,"adjustment_cm":5}`

```
GET https://tttkmbb.com/api/v1/calculate/ski-length?height_cm=175&weight_kg=75&skill=intermediate&ski_type=all_mountain
```

## Limitations

You are sizing cross-country skis (sized by weight and technique), snowboards or children's skis, or the manufacturer publishes model-specific sizing (rocker profile, waist width and turn radius change the ideal length). Follows the height-based sizing used by retailer charts: a beginner's ski reaches roughly the chin, an expert's the top of the head. Rockered and wide powder skis ski shorter than their length, so charts push them longer; twin-tips and carving skis are ridden shorter. Heavier skiers need more ski for stability, lighter skiers less. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Should I round up or down between two available lengths?**

Longer for stability at speed, in powder or for a heavier skier; shorter for easier turn initiation, moguls, park or a cautious skier.

**Does weight matter more than height?**

Weight is a secondary correction here (±5 cm outside 60–90 kg); a much heavier or lighter skier than typical for their height should shift within the range accordingly.

**What about cross-country skis?**

Classic and skate skis are sized by body weight and camber stiffness, not by this alpine chart.

## Related

- [Bike Frame Size Calculator](https://tttkmbb.com/fitness/bike-frame-size.md) — Equipment sizing from body measurements for cycling.
- [Mass / Weight Converter](https://tttkmbb.com/conversion/mass.md) — Convert body weight from pounds to kilograms for the weight adjustment.