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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.

When to use

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).

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.

Inputs

Parameter	Type	Required	Description
`value`	number	yes	Amount to convert, expressed in from_unit.
`from_unit`	enum: m/s \| km/h \| km/s \| mph \| ft/s \| kn \| mach	yes	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	yes	Unit to convert into (same symbols as from_unit).

Outputs

Output	Type	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.

Example

100 km/h to mph: {"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: {"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

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/speed (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/speed · Markdown: https://tttkmbb.com/conversion/speed.md · JSON definition: https://tttkmbb.com/conversion/speed.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="speed"
OpenAPI operationId: convert_speed
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

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 calculators

Pace Converter — Running pace (min/km, min/mi) instead of speed.
Speed, Distance & Time Calculator — Solve for speed, distance or time.
Length Converter — Convert the distance units alone.