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Speed Conversion
Tool Description
Speed Conversion is an online speed unit conversion tool that supports mutual conversion between meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots (kn), feet per second (ft/s), and Mach (Ma). Enter any value and unit to instantly view the corresponding results in all other units. Suitable for transportation, aerospace, marine navigation, physics studies, and more.
How to Use
- Enter a value
Type the value you want to convert in the input field, supporting integers and decimals, e.g.,
100,3.6 - Select source unit
Choose the speed unit of your value from the dropdown (m/s, km/h, mph, kn, ft/s, Ma)
- View results
Click the "Convert" button or press Enter, and the result area below will display the corresponding values in all units. Each result has a copy button for convenience.
Use Cases
- Transportation: Quickly compare km/h and mph, check foreign road sign speed limits, and convert vehicle dashboard readings
- Aviation & Maritime: Convert between knots, km/h, and m/s for marine speed, wind speed forecasts, and related scenarios
- Physics Study: Practice speed unit conversion in kinematics, and understand the conversion relationships between different unit systems
Key Advantages
- Free and No Install
Completely free to use right in your browser, with no software to download or install and no device storage consumed.
- Private and Secure
All conversions run locally in your browser using pure JavaScript math; your input never leaves your device, keeping your data private.
- All Units at Once
Enter one value and instantly get results for all units—m/s, km/h, mph, kn, ft/s, and Mach—without converting one by one.
- Mach Supported
Uniquely supports Mach (Ma) conversion with other common speed units, using the standard sea-level speed of sound (340.3 m/s) as the reference for aerospace needs.
- Easy Copy
Each result has a copy button on the right, letting you copy values with one click for use in documents, spreadsheets, or chat tools.
- Instant Response
Double-precision floating-point calculation delivers results instantly as you type or switch units, ideal for batch queries and classroom demos.
Speed Unit Conversion Relationships
The following table shows the conversion relationships between speed units, using meters per second (m/s) as the base unit:
| Unit Name | Abbr. | Conversion Relationship | Equivalent m/s |
|---|---|---|---|
| Meters per Second | m/s | Base unit | 1 |
| Kilometers per Hour | km/h | 1 km/h = 1/3.6 m/s | ≈ 0.277778 |
| Miles per Hour | mph | 1 mph = 0.44704 m/s | 0.44704 |
| Knots | kn | 1 kn = 1.852 km/h | ≈ 0.514444 |
| Feet per Second | ft/s | 1 ft/s = 0.3048 m/s | 0.3048 |
| Mach | Ma | 1 Ma = 340.3 m/s（standard atmosphere） | 340.3 |
Applications of Speed Units
Different industries and countries use different speed units. Understanding their applications helps you use the conversion tool more effectively.
| Speed Unit | Field | Typical Example |
|---|---|---|
| Meters per Second | Physics, Scientific Computing | Object velocity, wind speed |
| Kilometers per Hour | Transportation, Daily Travel | Car speed, high-speed rail |
| Miles per Hour | UK/US Transportation | Road speed limits, speedometers |
| Knots | Maritime, Aviation | Ship speed, ocean currents |
| Feet per Second | UK/US Engineering | Pipe flow rate, equipment specs |
| Mach | Aerospace | Aircraft cruise speed, missile speed |
About Mach Number (Ma)
Mach number (Ma) is the ratio of an object's speed to the local speed of sound, making it a dimensionless quantity. This tool uses the speed of sound under standard atmospheric conditions (15°C at sea level), which is 340.3 m/s, as the reference for calculations.
Note that the speed of sound varies with temperature and altitude: at higher altitudes with lower temperatures, the speed of sound is slower, meaning the same Mach number corresponds to a lower actual speed. For example, at 11,000 m altitude (-56.5°C), the speed of sound is only about 295 m/s, so Ma=1 corresponds to approximately 295 m/s rather than the sea-level 340.3 m/s. Mach numbers are primarily used in aerospace to describe flight speeds.
FAQ
1 Mach (Ma) ≈ 340.3 m/s ≈ 1,225 km/h (standard atmosphere, 15°C at sea level). Mach number is not a fixed value; it varies with temperature and altitude. In high-altitude, low-temperature environments, the speed of sound is slower, so the same Mach number corresponds to fewer km/h. For example, the Concorde supersonic airliner cruised at approximately Mach 2.04, equivalent to about 2,180 km/h.
A knot (kn) is a speed unit commonly used in maritime and aviation contexts, defined as one nautical mile per hour. 1 nautical mile = 1.852 km, so 1 kn = 1.852 km/h ≈ 0.514 m/s. For example, a cargo ship cruising at 20 knots travels at approximately 37 km/h.
1 mph = 1.609344 km/h, roughly 1 mph ≈ 1.61 km/h. Common comparisons: US highway speed limit 65 mph ≈ 105 km/h, 100 mph ≈ 161 km/h. When you see mph values on an imported car's dashboard, multiply by 1.6 to get the approximate km/h.
100 km/h = 100 ÷ 3.6 ≈ 27.78 m/s. Conversion formulas: km/h ÷ 3.6 = m/s, m/s × 3.6 = km/h. For example, Usain Bolt's top instantaneous speed during the 100m sprint was about 44.72 km/h, which converts to 12.42 m/s.
No. All conversion calculations run entirely in your browser using pure JavaScript math. Your input data never leaves your device.
This tool uses JavaScript double-precision floating-point numbers (64-bit IEEE 754) for calculations, which is sufficiently accurate for the vast majority of everyday scenarios. Mach number conversion uses the standard atmosphere sea-level speed of sound (340.3 m/s). Decimal portions are capped at 6 significant decimal places, and excessively long decimals are automatically truncated. For extremely large or small values, there may be minor errors due to floating-point precision limitations, but this has virtually no practical impact.
It supports 6 common speed units: meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots (kn), feet per second (ft/s), and Mach (Ma). Enter a value in one unit and the others are calculated automatically—no need to pick a target unit.
No. The tool is completely free and requires no registration or login. Just open the page and start using it—no ads, no personal information requested, ideal for quick lookups and teaching demos.
Yes. The page is responsive and works on phones, tablets, and desktop browsers alike. On mobile, simply tap the input, choose a unit, and tap convert to see results, just like on desktop.
Batch input is not yet supported. The current version converts one value at a time, but a single entry yields results for all 6 units at once, which covers most daily and teaching scenarios. For bulk processing, enter values repeatedly or use a formula.
Because the speed of sound varies with the environment. Mach is a ratio of speed to the local speed of sound, which depends on temperature and altitude. This tool uses the standard-atmosphere (15°C sea level) speed of sound of 340.3 m/s, suitable for general aviation reference; at high altitude with low temperature the actual speed of sound is lower, so the same Mach corresponds to a smaller speed.
Click the copy icon on the right of the result box. Each unit result has a copy button that copies the value to your clipboard with one click, ready to paste into a document, spreadsheet, or chat window without manually selecting text.
Content last updated：2026-07-16
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