# Speed Converter

> Converts speeds between m/s, km/h, km/s, mph, ft/s, knots and Mach number using exact factors (1 mph = 0.44704 m/s, 1 kn = 1852/3600 m/s) and 340.294 m/s for Mach 1 at sea level.

- Calculator id: `speed` · Category: Unit Conversion (`conversion`) · Tool name: `convert_speed`
- Canonical page: https://tttkmbb.com/conversion/speed · This document: https://tttkmbb.com/conversion/speed.md · JSON definition: https://tttkmbb.com/conversion/speed.json

## Purpose

Converts speeds between m/s, km/h, km/s, mph, ft/s, knots and Mach number using exact factors (1 mph = 0.44704 m/s, 1 kn = 1852/3600 m/s) and 340.294 m/s for Mach 1 at sea level.

**Use when:** You need a vehicle, wind, running or aircraft speed in another unit, e.g. km/h to mph, knots to km/h or m/s to ft/s.

**Do not use when:** You need running pace (min/km or min/mile, use pace-converter) or to derive speed from distance and time (use speed-distance-time).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `value` | number |  | required | Amount to convert, expressed in from_unit. |
| `from_unit` | enum: m/s \| km/h \| km/s \| mph \| ft/s \| kn \| mach |  | required | Unit of the input value. Accepted symbols: m/s, km/h, km/s, mph, ft/s, kn, mach; spelled-out names and common abbreviations are accepted too. |
| `to_unit` | enum: m/s \| km/h \| km/s \| mph \| ft/s \| kn \| mach |  | required | Unit to convert into (same symbols as from_unit). |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `result` | number |  | Converted value expressed in to_unit (rounded to 6 decimals; see result_text for very small or very large values). |
| `result_text` | string |  | The conversion as text with 6 significant figures, e.g. "5 mi = 8.04672 km". |
| `formula` | string |  | Relation used, e.g. "1 mi = 1.609344 km". |
| `factor` | number |  | Multiplier from from_unit to to_unit (result = value × factor); absent for non-linear conversions. |
| `conversion_table` | object |  | The input value expressed in every supported speed unit (6 significant figures), keyed by unit symbol. |

## Formula

`result = value × factor, factor = (1 from_unit in m/s) / (1 to_unit in m/s)`

Mach is not a fixed unit: 340.294 m/s is the ICAO standard-atmosphere speed of sound at sea level and 15 °C; it falls to about 295 m/s at cruising altitude.

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-23)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-23)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-23)

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/speed?value=…&from_unit=…&to_unit=…`
- `POST https://tttkmbb.com/api/v1/calculate/speed` 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/speed · OpenAPI operationId `convert_speed` 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": "speed", "inputs": {…}}`

## Example

- 100 km/h to mph: inputs `{"value":100,"from_unit":"km/h","to_unit":"mph"}` → `{"result":62.137119,"formula":"1 km/h = 0.6213711922 mph","conversion_table":{"m/s":27.7778,"kn":53.9957,"ft/s":91.1344}}`
- 25 knots to km/h: inputs `{"value":25,"from_unit":"kn","to_unit":"km/h"}` → `{"result":46.3,"factor":1.852,"conversion_table":{"mph":28.7695,"m/s":12.8611}}`

```
GET https://tttkmbb.com/api/v1/calculate/speed?value=100&from_unit=km%2Fh&to_unit=mph
```

## Limitations

You need running pace (min/km or min/mile, use pace-converter) or to derive speed from distance and time (use speed-distance-time). Mach is not a fixed unit: 340.294 m/s is the ICAO standard-atmosphere speed of sound at sea level and 15 °C; it falls to about 295 m/s at cruising altitude. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**What is a knot exactly?**

One nautical mile (1852 m) per hour, i.e. 0.514444 m/s or 1.150779 mph.

**Is Mach constant?**

No; Mach number depends on air temperature. The factor here is for sea level in the international standard atmosphere (340.294 m/s ≈ 1225 km/h).

## Related

- [Pace Converter](https://tttkmbb.com/fitness/pace-converter.md) — Running pace (min/km, min/mi) instead of speed.
- [Speed, Distance & Time Calculator](https://tttkmbb.com/physics/speed-distance-time.md) — Solve for speed, distance or time.
- [Length Converter](https://tttkmbb.com/conversion/length.md) — Convert the distance units alone.