Speed Converter
Convert between mph, km/h, m/s, knots, and feet per second.
What Is the Speed Converter?
The Speed Converter converts between all major speed units: meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots (nautical miles per hour), feet per second (ft/s), and Mach number. Useful for automotive, aviation, maritime, and scientific applications.
Formula
How to Use
Enter a speed value in any supported unit. The converter instantly shows all equivalents. Common conversions include mph to km/h (for international travel), knots to km/h (maritime/aviation), and m/s to mph (physics problems).
Example Calculation
60 mph: = 60×1.609 = 96.56 km/h = 60/1.151 = 52.14 knots = 60×1.467 = 88 ft/s = 96.56/343 ≈ Mach 0.082 at sea level. Speed of sound (343 m/s): = 1234.8 km/h = 767.3 mph = 666.7 knots.
Understanding Speed Converter
Speed measures the rate of change of position — distance traveled per unit time. The SI unit is meters per second (m/s), but everyday life uses kilometers per hour (km/h) or miles per hour (mph) for vehicles, knots for aircraft and ships, and specialized units like Mach numbers for supersonic flight. Converting between these is essential for international travel, cross-discipline engineering, and scientific work.
The conversion between km/h and mph is one of the most practically important for travelers: 1 mph ≈ 1.609 km/h, so 60 mph ≈ 96.6 km/h. A quick mental approximation: multiply mph by 1.6 for km/h, or multiply km/h by 0.6 for mph. Speed limits in the UK (70 mph) correspond to about 113 km/h on the continent.
In aviation, the speed of sound in air is a critical reference. At sea level (15°C), sound travels at approximately 340 m/s = 1224 km/h = 661 knots. Jet aircraft cruise at about 900 km/h (Mach 0.83), just below the speed of sound. Concorde flew at Mach 2 (~2180 km/h), and experimental vehicles like the SR-71 Blackbird reached Mach 3.3 (~3540 km/h).
Frequently Asked Questions
What is a knot?
A knot is one nautical mile per hour. 1 nautical mile = 1852 m (based on 1 arcminute of latitude). Knots are used in aviation and maritime navigation because nautical miles align with geographic coordinates.
What is Mach number?
Mach number = speed / speed of sound in the medium. Mach 1 at sea level (20°C) ≈ 343 m/s = 1235 km/h = 767 mph. At altitude and low temperature, Mach 1 is slower. Supersonic = Mach > 1, hypersonic = Mach > 5.
How does the speed of light compare to everyday speeds?
Light travels at 299,792,458 m/s ≈ 300,000 km/s. A commercial aircraft (900 km/h) moves at about 0.000001c. Even the fastest spacecraft (New Horizons, ~58,000 km/h) travels at only 0.00005c.
Why do different countries use different speed units?
The US and UK use mph for road speeds. Most countries use km/h. Aviation and maritime navigation worldwide use knots. Physics uses m/s (SI unit).
Is this converter free?
Yes, completely free with no registration required.