Speed units vary by context: km/h for driving, mph in the US and UK, m/s in physics, and knots in aviation. Understanding how they relate is essential.
Kilometers per Hour and Miles per Hour
km/h is used on road signs worldwide except in the US and UK. 1 mph = 1.609344 km/h exactly. A typical highway speed is 100–120 km/h (62–75 mph).
Meters per Second
The m/s is the SI unit for speed. To convert km/h to m/s, divide by 3.6. So 100 km/h = 27.78 m/s. The speed of light is approximately 3 × 10⁸ m/s.
Knots: Maritime and Aviation
A knot is one nautical mile per hour. 1 nautical mile = 1,852 m exactly. So 1 knot = 1.852 km/h = 1.15078 mph. Aviation uses knots because nautical miles align with latitude coordinates on charts.
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Frequently Asked Questions
How do I convert km/h to mph?
Divide km/h by 1.60934. For example, 100 km/h ÷ 1.609 = 62.14 mph.
Why do pilots use knots instead of mph?
Knots align with Earth's coordinate system. One nautical mile = one minute of latitude, making navigation straightforward on charts.