Speed Converter
Speed Converter — Convert m/s, km/h, mph, Knots & More
Our free online Speed Converter lets you instantly convert between 31+ units of speed and velocity — from everyday units like kilometers per hour and miles per hour to nautical knots, Mach numbers, and the speed of light. Whether you need to convert km/h to mph, m/s to km/h, knots to mph, or Mach to meters per second, this tool delivers instant and accurate results.
Speed is the rate of change of distance with respect to time. It is used in transportation, aviation, marine navigation, meteorology, and physics. Units span multiple systems:
- SI metric: meter per second (m/s), kilometer per hour (km/h), kilometer per second (km/s)
- Imperial / US: mile per hour (mph), foot per second (ft/s), yard per second
- Marine & aviation: knot (kt) = 1 nautical mile per hour
- Acoustic: Mach number (ratio to speed of sound in air)
- Scientific extremes: speed of light in vacuum (c ≈ 299,792,458 m/s)
All conversions use internationally standardized factors and high-precision arithmetic, reliable for transportation, navigation, aviation, meteorology, physics, and everyday speed calculations.
Common Speed Conversion Reference
Here are the most frequently used speed conversions for quick reference:
- 1 m/s = 3.6 km/h = 2.23694 mph = 1.94384 knots
- 1 km/h = 0.277778 m/s = 0.621371 mph = 0.539957 knots
- 1 mph = 1.60934 km/h = 0.44704 m/s = 0.868976 knots
- 1 knot = 1.852 km/h = 1.15078 mph = 0.514444 m/s
- Speed of sound (20°C, 1 atm) ≈ 343.6 m/s = 1,236 km/h = 767.9 mph = Mach 1
- Speed of light in vacuum = 299,792,458 m/s ≈ 1.08 × 10⁹ km/h
- 60 mph = 96.561 km/h = 26.822 m/s
- 100 km/h = 62.137 mph = 27.778 m/s = 53.996 knots
Frequently Asked Questions — Speed Converter
Question: How do I use the Speed Converter?
Answer: Select the unit you are converting from in the left list and the unit to convert to in the right list, then type your value. The result appears instantly across all listed units.
Question: How do I convert km/h to mph?
Answer: Multiply the km/h value by 0.621371 to get mph. For example, 100 km/h × 0.621371 = 62.14 mph. Conversely, multiply mph by 1.60934 to get km/h.
Question: How do I convert m/s to km/h?
Answer: Multiply the m/s value by 3.6 to get km/h. For example, 10 m/s × 3.6 = 36 km/h. To convert km/h to m/s, divide by 3.6.
Question: What is a knot and why is it used?
Answer: A knot (kt or kn) is one nautical mile per hour, equal to exactly 1.852 km/h or approximately 1.15078 mph. Knots are the international standard for maritime and aviation speed because nautical miles are tied to degrees of latitude, making navigation calculations simpler.
Question: What is Mach 1?
Answer: Mach 1 is the speed of sound in the medium at the local conditions. In air at 20°C and sea level, Mach 1 ≈ 343.6 m/s (1,236 km/h or 767.9 mph). At higher altitudes where air is colder and thinner, the speed of sound decreases. Objects traveling at or above Mach 1 are said to be supersonic.
Question: What is the speed of light?
Answer: The speed of light in a vacuum is exactly 299,792,458 meters per second (approximately 300,000 km/s or 186,282 miles per second). It is the universal speed limit according to special relativity — no physical object with mass can reach this speed.
Question: How fast is 60 miles per hour in km/h?
Answer: 60 miles per hour equals approximately 96.561 km/h (60 × 1.60934). This is a common reference: US highway speed limits are often 60–70 mph, equivalent to 97–113 km/h.
Question: What is cosmic velocity?
Answer: Cosmic velocities are critical speeds for space travel. The first cosmic velocity (~7.9 km/s) is the minimum orbital speed. The second (~11.2 km/s) is escape velocity from Earth. The third (~16.7 km/s) is the speed needed to escape the solar system.
Question: How accurate are the speed conversions in this tool?
Answer: All conversions use internationally standardized conversion factors with up to 12 significant digits of precision, suitable for transportation, navigation, aviation, meteorology, physics, and engineering.