Speed Converter
Convert between various speed units including meters per second, kilometers per hour, miles per hour, knots and more
Common Speed Conversions
1 km/h = 0.621371 mph
To convert kilometers per hour to miles per hour, multiply the km/h value by 0.621371.
Example: 100 km/h = 100 × 0.621371 = 62.1371 mph
1 mph = 1.60934 km/h
To convert miles per hour to kilometers per hour, multiply the mph value by 1.60934.
Example: 60 mph = 60 × 1.60934 = 96.5604 km/h
1 m/s = 3.6 km/h
To convert meters per second to kilometers per hour, multiply the m/s value by 3.6.
Example: 20 m/s = 20 × 3.6 = 72 km/h
Speed Conversion Reference Table
| Unit | m/s | km/h | mph | ft/s | knots | Mach |
|---|---|---|---|---|---|---|
| 1 m/s | 1 | 3.6 | 2.23694 | 3.28084 | 1.94384 | 0.00293 |
| 1 km/h | 0.277778 | 1 | 0.621371 | 0.911344 | 0.539957 | 0.000814 |
| 1 mph | 0.44704 | 1.60934 | 1 | 1.46667 | 0.868976 | 0.00131 |
| 1 ft/s | 0.3048 | 1.09728 | 0.681818 | 1 | 0.592484 | 0.000894 |
| 1 knot | 0.514444 | 1.852 | 1.15078 | 1.68781 | 1 | 0.00151 |
| 1 Mach | 340.29 | 1225.04 | 761.207 | 1116.44 | 661.474 | 1 |
| Speed of Light (c) | 299,792,458 | 1,079,252,848.8 | 670,616,629 | 983,571,056 | 582,749,918 | 880,991 |
About Speed Units
The metric system uses the following units for speed:
- Meter per Second (m/s): The standard unit of speed in the International System of Units (SI). Used in scientific contexts and physics calculations.
- Kilometer per Hour (km/h): The most common unit for everyday speed measurements in countries using the metric system. Used for vehicle speeds, speed limits, and weather reports.
- Centimeter per Second (cm/s): Used for slower speeds in scientific contexts.
The imperial and US customary systems use:
- Mile per Hour (mph): The standard unit for vehicle speeds and speed limits in the United States, United Kingdom, and some other countries. Also used for wind speeds in weather reports.
- Foot per Second (ft/s): Used in engineering contexts in the US and sometimes in ballistics.
- Inch per Second (in/s): Used for slower motions in certain engineering and manufacturing contexts.
Specialized units used in maritime and aviation contexts:
- Knot (kn): One nautical mile per hour, approximately 1.15078 mph or 1.852 km/h. Standard unit for maritime navigation and aviation.
- Mach: The ratio of an object's speed to the speed of sound in the surrounding medium (typically air). Mach 1 at sea level at 15°C is approximately 340.29 m/s (761.2 mph, 1,225 km/h). Used in aviation and aeronautics.
Special units used in scientific contexts:
- Speed of Light (c): Approximately 299,792,458 meters per second (m/s) in vacuum. The maximum speed at which all massless particles and changes in the associated fields can travel in vacuum. It is a fundamental constant in physics.
Frequently Asked Questions
To convert kilometers per hour to miles per hour, multiply the km/h value by 0.621371. For example, 100 km/h = 100 × 0.621371 = 62.1371 mph.
A knot is one nautical mile per hour, while a mile per hour refers to statute miles per hour. One knot equals approximately 1.15078 miles per hour. Knots are commonly used in maritime navigation and aviation because the nautical mile is based on the Earth's circumference, making it convenient for navigation across the globe.
To convert meters per second to kilometers per hour, multiply the m/s value by 3.6. This is because there are 3,600 seconds in an hour (60 seconds × 60 minutes) and 1,000 meters in a kilometer. Therefore, 1 m/s = 3.6 km/h. For example, 20 m/s = 20 × 3.6 = 72 km/h.
Mach speed is a measure of speed relative to the speed of sound in a given medium. Mach 1 means an object is traveling at the speed of sound, Mach 2 is twice the speed of sound, and so on. At sea level at 15°C (59°F), Mach 1 is approximately 340.29 meters per second (761.2 mph or 1,225 km/h). The exact value of Mach speed varies with temperature and atmospheric conditions.
The speed of sound varies with altitude primarily due to changes in temperature. Sound travels faster in warmer air and slower in colder air. As altitude increases, air temperature generally decreases in the troposphere (the lowest layer of Earth's atmosphere), causing the speed of sound to decrease. At higher altitudes in the stratosphere, the temperature begins to increase, which can cause the speed of sound to increase again. Air density and composition also affect the speed of sound but to a lesser extent than temperature.