# Projector Throw Distance Calculator

> Uses a projector's throw ratio (distance ÷ image width) to find the projection distance for a given screen width, or the image width for a given distance, and reports the image height and diagonal for the chosen aspect ratio.

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

## Purpose

Uses a projector's throw ratio (distance ÷ image width) to find the projection distance for a given screen width, or the image width for a given distance, and reports the image height and diagonal for the chosen aspect ratio.

**Use when:** You are placing a projector or choosing a screen size and know the lens throw ratio from the spec sheet, or want to know what throw ratio a room needs.

**Do not use when:** You need TV seating distances (use tv-viewing-distance) or lens-shift/keystone geometry; zoom lenses have a throw-ratio range, so run the calculator at both ends.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `throw_ratio` | number |  | required | Lens throw ratio = throw distance / image width (e.g. 1.5 means 1.5 m of distance per metre of width; 0.25 for an ultra-short-throw). (min 0.1, max 20) |
| `screen_width_m` | number | m | optional | Desired image width. Give this to get the throw distance (takes precedence over throw_distance_m). (> 0, max 100) |
| `throw_distance_m` | number | m | optional | Lens-to-screen distance. Give this alone to get the image size; with the width it also yields the throw ratio the room needs. (> 0, max 200) |
| `aspect_ratio` | enum: 16:9 \| 16:10 \| 4:3 \| 2.35:1 |  | optional, default "16:9" | Width-to-height ratio of the screen or image. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `throw_distance_m` | number | m | Lens to screen = throw_ratio × width. |
| `throw_distance_ft` | number | ft | Same distance in feet. |
| `screen_width_m` | number | m | Projected image width. |
| `screen_height_m` | number | m | width / aspect ratio. |
| `screen_diagonal_m` | number | m | √(width² + height²). |
| `screen_diagonal_in` | number | in | Diagonal in inches, as screens are sold. |
| `required_throw_ratio` | number |  | throw_distance_m / screen_width_m when both are given, to compare with the lens. |
| `throw_type` | string |  | Ultra short throw (<0.4), short throw (0.4–1), standard (1–2) or long throw (>2). |

## Formula

`throw_ratio = distance / width; distance = throw_ratio × width; width = distance / throw_ratio; height = width / aspect; diagonal = √(width² + height²); 1 m = 39.3701 in`

Throw ratio is measured from the lens to the screen surface; for zoom lenses use the minimum and maximum ratios from the data sheet. Ultra-short-throw projectors quote the ratio from the lens exit, typically 20–40 cm behind the front of the unit.

## Data Sources

- Throw (projector) – throw ratio definition (Wikipedia) — https://en.wikipedia.org/wiki/Throw_(projector) (reference, retrieved 2026-09-24)
- Projector Central – Projection calculator (throw distance) — https://www.projectorcentral.com/projection-calculator-pro.cfm (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/projector-throw?throw_ratio=…`
- `POST https://tttkmbb.com/api/v1/calculate/projector-throw` 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/projector-throw · OpenAPI operationId `calculate_projector_throw_distance` 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": "projector-throw", "inputs": {…}}`

## Example

- Throw ratio 1.5, 2 m wide 16:9 image: inputs `{"throw_ratio":1.5,"screen_width_m":2}` → `{"throw_distance_m":3,"throw_distance_ft":9.84,"screen_width_m":2,"screen_height_m":1.125,"screen_diagonal_m":2.295,"screen_diagonal_in":90.3,"throw_type":"Standard throw"}`
- Throw ratio 1.2 at 4 m, 16:9: inputs `{"throw_ratio":1.2,"throw_distance_m":4}` → `{"throw_distance_m":4,"screen_width_m":3.333,"screen_height_m":1.875,"screen_diagonal_m":3.824,"screen_diagonal_in":150.6}`

```
GET https://tttkmbb.com/api/v1/calculate/projector-throw?throw_ratio=1.5&screen_width_m=2
```

## Limitations

You need TV seating distances (use tv-viewing-distance) or lens-shift/keystone geometry; zoom lenses have a throw-ratio range, so run the calculator at both ends. Throw ratio is measured from the lens to the screen surface; for zoom lenses use the minimum and maximum ratios from the data sheet. Ultra-short-throw projectors quote the ratio from the lens exit, typically 20–40 cm behind the front of the unit. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Where is the throw ratio on a spec sheet?**

Usually as a range such as '1.32–1.72:1' for zoom lenses; the first number is the widest image from a given distance, the second the most zoomed-in.

**Does the ratio use width or diagonal?**

Width. Distances quoted per inch of diagonal depend on the aspect ratio, which is why this calculator asks for it.

## Related

- [TV Viewing Distance Calculator](https://tttkmbb.com/everyday/tv-viewing-distance.md) — Seating distance for the resulting image size.
- [Aspect Ratio Calculator](https://tttkmbb.com/everyday/aspect-ratio.md) — Image dimensions from a ratio.
- [Screen PPI Calculator](https://tttkmbb.com/everyday/screen-ppi.md) — Pixel density of a display of that size.