# Speed unit convert

`speed-unit-convert` · version 1.0.0 · Units & sizes · free, no key needed

Convert an exact decimal speed among metres per second, kilometres per hour, mph, knots, and feet per second.

**Use when you need to: convert speed units · metres per second to kilometres per hour · kilometres per hour to miles per hour.**

## Decide before calling

Read the [versioned contract](/v1/tools/speed-unit-convert/versions/1.0.0) and the supported scope below. Reuse `speed-unit-convert@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `speed-unit-convert@1.0.0` for convert speed units. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- convert speed units
- metres per second to kilometres per hour
- kilometres per hour to miles per hour
- miles per hour to knots
- knots to metres per second
- feet per second speed conversion
- exact velocity unit conversion

## Not supported

- convert acceleration units
- convert pace or travel duration
- convert non-standard nautical miles

## Behavior

- Input value is a non-negative ASCII decimal in plain notation with at most 30 significant digits; signs, exponent notation, whitespace, and separators are rejected.
- Conversions use exact SI definitions: 1 kilometre = 1000 metres, 1 hour = 3600 seconds, 1 international mile = 1609.344 metres, 1 international nautical mile = 1852 metres, and 1 international foot = 0.3048 metres.
- exact_numerator/exact_denominator is the reduced exact rational result; value is rounded to decimal_places digits after the point using round-half-up, including trailing zeroes.
- Unit identity conversions still reduce the input decimal to an exact fraction. The input object is never mutated.
- More than 32 UTF-8 bytes in value is limit_exceeded before decimal syntax validation; decimal_places is an integer from 0 through 18.

## Input

- `value` (string, required): min length 1; max length 32; pattern `^(0|[1-9][0-9]*)(\.[0-9]+)?$`
- `from_unit` (one of "metres_per_second", "kilometres_per_hour", "miles_per_hour", "knots", "feet_per_second", required)
- `to_unit` (one of "metres_per_second", "kilometres_per_hour", "miles_per_hour", "knots", "feet_per_second", required)
- `decimal_places` (integer, required): min 0; max 18

## Output

- `value` (string, required): pattern `^[0-9]+(\.[0-9]+)?$`
- `unit` (one of "metres_per_second", "kilometres_per_hour", "miles_per_hour", "knots", "feet_per_second", required)
- `exact_numerator` (string, required): pattern `^[0-9]+$`
- `exact_denominator` (string, required): pattern `^[1-9][0-9]*$`
- `decimal_places` (integer, required): min 0; max 18

## Limits

- max value bytes: 32
- max decimal places: 18

## Example

Request input:

```json
{
  "value": "1",
  "from_unit": "metres_per_second",
  "to_unit": "kilometres_per_hour",
  "decimal_places": 3
}
```

Response:

```json
{
  "result": {
    "value": "3.600",
    "unit": "kilometres_per_hour",
    "exact_numerator": "18",
    "exact_denominator": "5",
    "decimal_places": 3
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "speed-unit-convert",
  "version": "1.0.0",
  "input": {
    "value": "1",
    "from_unit": "metres_per_second",
    "to_unit": "kilometres_per_hour",
    "decimal_places": 3
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/speed-unit-convert/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"value":"1","from_unit":"metres_per_second","to_unit":"kilometres_per_hour","decimal_places":3}'
```

The machine-readable contract is at [/v1/tools/speed-unit-convert/versions/1.0.0](/v1/tools/speed-unit-convert/versions/1.0.0).

### CLI

```sh
node cli.mjs run speed-unit-convert 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

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