Speed converter tool. Convert between different speed units including mph, km/h, knots, feet per second, and Mach number. Fast, accurate, and easy to use for travel, sports, and science.
Speed conversion is straightforward once you understand the relationship between different units. Here's how to get precise results:
Speed is measured differently depending on the domain. In everyday life, most countries use km/h (kilometers per hour) for road speeds, while the United States, UK, and a few others use mph (miles per hour). In aviation and maritime contexts, knots (nautical miles per hour) are the standard — one knot equals one nautical mile per hour, which is based on the Earth's circumference and is approximately 1.852 km/h. For high-speed aircraft and spacecraft, Mach number is used, which represents the ratio of speed to the speed of sound in the surrounding medium. Mach 1 is approximately 1,235 km/h at sea level, but changes with altitude and temperature. Understanding these conversions is essential for pilots, sailors, meteorologists, and travelers.
Multiply the km/h value by 0.621371. For example: 100 km/h × 0.621371 = 62.14 mph. To convert mph to km/h, divide by 0.621371 (or multiply by 1.60934).
Knots are based on nautical miles, which correspond to one minute of latitude. This makes navigation calculations simpler — one knot equals one nautical mile per hour, and nautical miles align directly with latitude and longitude coordinates on maps and charts. The standard has been in use for centuries and remains the international standard for aviation and maritime navigation.
Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. Mach 1 equals the speed of sound, which varies with temperature and altitude (about 1,235 km/h at sea level, but only about 1,062 km/h at 10,000 meters). Mach 2 is twice the speed of sound, and so on. Mach numbers are used in aerodynamics and aerospace because they indicate compressibility effects on the vehicle.
The speed of light in a vacuum is exactly 299,792,458 meters per second, which equals approximately 1,079,252,848.8 km/h (about 1.08 billion km/h). This is the universal speed limit — nothing with mass can reach this speed.
Feet per second (ft/s) is an imperial unit primarily used in the US for engineering and ballistics. One ft/s equals 0.3048 meters per second (m/s), the SI unit. To convert ft/s to m/s, multiply by 0.3048. Meters per second is the standard scientific unit for speed and is used in physics equations like F=ma.
Yes! The converter supports Mach values up to Mach 25 and beyond. At Mach 10 (about 12,350 km/h at sea level), you're in the hypersonic range — this is the speed of intercontinental ballistic missiles and some experimental aircraft. Our tool converts seamlessly between all supported units regardless of magnitude.