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Speed Converter

Convert between mph, km/h, m/s, and knots instantly

Miles per hour (mph): 60.00
Kilometers per hour (km/h): 96.56
Meters per second (m/s): 26.82
Knots (kn): 52.14
Dr. Robert Chen

Reviewed by Dr. Robert Chen, Ph.D.

Aerospace Engineer | Transportation Physics Expert

Last Updated: November 24, 2025

Understanding Speed Units

Speed is the rate at which an object covers distance. Different fields and regions use different units, making conversion essential for travel, science, and engineering.

Common Speed Units

1 mph ā‰ˆ 1.609 km/h
1 knot ā‰ˆ 1.15 mph ā‰ˆ 1.852 km/h
1 m/s = 3.6 km/h ā‰ˆ 2.237 mph

Why Knots?

You might wonder why planes and ships use "knots" instead of mph or km/h. It's because knots are based on the geometry of the Earth. One knot is one nautical mile per hour, and one nautical mile is exactly one minute of latitude. This makes navigation calculations on charts much simpler for pilots and sailors. Traveling at 60 knots means you are covering 1 degree of latitude every hour.

Mach Number

In high-speed aviation, we use Mach numbers. Mach 1 is the speed of sound. However, the speed of sound changes with temperature (and thus altitude). At sea level, Mach 1 is about 761 mph (1225 km/h). At 30,000 feet, where it's colder, Mach 1 is only about 678 mph (1091 km/h). This is why Mach is a ratio, not a fixed speed.

šŸ’” Expert Tips from Dr. Chen

The "Rule of 3.6": To convert m/s to km/h, simply multiply by 3.6. To go from km/h to m/s, divide by 3.6. This is because there are 3600 seconds in an hour and 1000 meters in a kilometer (3600/1000 = 3.6). It's the most useful shortcut in physics class!

Driving Abroad: If you're used to mph and driving in a km/h country, remember that 100 km/h is roughly 62 mph. Highway speeds of 120 km/h are about 75 mph. Don't panic when you see "100" on the sign!

Wind Speed: Weather reports often give wind speed in knots or m/s, while the public thinks in mph or km/h. A "force 8 gale" (34-40 knots) is about 39-46 mph. Knowing the conversion helps you understand the severity of storms.

āš ļø Common Mistakes to Avoid

  • Confusing mph and km/h: This is the most dangerous error for drivers. Thinking the "50" sign means 50 mph when it means 50 km/h (31 mph) will get you a ticket. Thinking "100" means 100 mph when it means 100 km/h will get you in an accident.
  • Mixing up Knots and mph: They are close (1 kt = 1.15 mph) but different enough to matter. A boat doing 20 knots is faster than a car doing 20 mph. In long-distance travel, this 15% difference adds up to hours of arrival time error.
  • Ignoring Direction (Velocity): Remember that speed is just a number (scalar), while velocity includes direction (vector). In navigation, 50 knots North is a completely different velocity from 50 knots East, even if the speed is the same.

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Frequently Asked Questions

What is the difference between speed and velocity?
Speed is a scalar quantity that measures how fast an object is moving (e.g., 60 mph). Velocity is a vector quantity that includes both speed and direction (e.g., 60 mph North). In everyday conversation and most basic calculations, we use 'speed', but in physics and navigation, the direction (velocity) is crucial.
How do I convert km/h to mph?
To convert kilometers per hour (km/h) to miles per hour (mph), multiply by 0.621371. A quick mental approximation is to multiply by 0.6 (or divide by 1.6). For example, 100 km/h is approximately 62 mph. This is essential for drivers crossing borders between metric and imperial countries.
What is a 'knot' and where is it used?
A knot (kt) is a unit of speed equal to one nautical mile per hour, or exactly 1.852 km/h (approx 1.15 mph). It is the standard unit for maritime and aviation navigation. The term comes from the old practice of counting knots on a rope trailed from a ship to measure speed.
What is Mach number?
Mach number is the ratio of an object's speed to the speed of sound in the surrounding fluid. Mach 1 is the speed of sound (approx 343 m/s or 767 mph at sea level). Speeds below Mach 1 are subsonic, above Mach 1 are supersonic. Mach depends on temperature and altitude, so it's not a fixed speed unit like mph.
Why do scientists use meters per second (m/s)?
Meters per second (m/s) is the SI derived unit for speed. It simplifies physics calculations because it relates directly to meters (distance) and seconds (time) without extra conversion factors. For example, in F=ma calculations, acceleration is in m/sĀ². Using km/h would require messy conversions.

šŸ“š Expert References & Further Reading

  1. NIST - SI Units - Speed and Velocity. https://www.nist.gov/
  2. NASA - Speed of Sound and Mach Number. https://www.grc.nasa.gov/
  3. FAA - Pilot's Handbook of Aeronautical Knowledge. https://www.faa.gov/