Speed Converter
Convert between mph, km/h, m/s, and knots.
Quick reference
- 1 m/s = 3.6 km/h ≈ 2.24 mph
- 1 mph ≈ 1.61 km/h ≈ 0.447 m/s
- 1 knot ≈ 1.15 mph ≈ 1.852 km/h
- 60 mph ≈ 96.6 km/h
About this converter
Speed limits, wind reports, and vehicle specs all get quoted in different units depending on where you are and what you're looking at: mph on US road signs, km/h almost everywhere else, knots for anything on the water or in the air. This converts between all of those plus the plain SI unit, meters per second.
Knots specifically come from navigation, not from any land-based system. A knot is one nautical mile per hour, and a nautical mile is defined as one minute of latitude, so it ties directly into how ships and planes calculate position from lat/long coordinates. It has nothing to do with statute miles, which is why converting knots to mph isn't a clean round number.
Frequently asked questions
- What's a knot, exactly?
- One nautical mile per hour, about 1.15 mph. It's used at sea and in the air specifically because it ties directly to a minute of latitude, which makes navigation math simpler.
- Why do planes use knots for speed but feet for altitude?
- Aviation kept both conventions from early 20th-century navigation practice, and international standards never fully unified them, even in countries that use metric for everything else on the ground.
- Is the speed of sound (Mach 1) a fixed mph number?
- No, and this surprises people. Mach 1 depends on air temperature, so it's faster at sea level (around 767 mph) than at cruising altitude (around 660 mph), where the air is colder. Mach isn't really a unit of speed on its own, it's a ratio to whatever the local speed of sound happens to be.
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