Speed Converter
Convert between km/h, mph, m/s, knots, and ft/s.
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This converter handles speed across the units most commonly used for travel, sports, and navigation â kilometers per hour, miles per hour, meters per second, knots, and feet per second â converting through meters per second as the common base unit.
Road speed conversions are the most frequent use case: kilometers per hour dominates outside the US, while miles per hour is standard within it. A quick approximation â multiply km/h by 0.62 to estimate mph, or divide mph by 0.62 (roughly multiply by 1.6) to estimate km/h â gets close, but this calculator uses the exact factor (0.621371) for precise results.
Meters per second is the standard scientific unit for speed, commonly used in physics problems and technical specifications, while feet per second serves a similar role in some engineering and ballistics contexts within imperial-unit countries.
Knots (nautical miles per hour) are the standard unit for maritime and aviation speed worldwide, based on the nautical mile rather than the standard (statute) mile â 1 knot equals about 1.15 mph or 1.852 km/h, meaning a speed in knots is always somewhat higher than the same numeric speed in mph would suggest.
For context on typical speeds: highway driving is commonly 100-120 km/h (62-75 mph), a fast marathon runner's pace works out to roughly 20 km/h (12 mph), and commercial jet cruising speed is typically 800-900 km/h (500-560 mph, or roughly Mach 0.8) â useful benchmarks when a converted number needs a sanity check.
How do I convert km/h to mph?
Multiply km/h by 0.621371 to get mph.
How do I convert mph to km/h?
Multiply mph by 1.60934 to get km/h â the exact inverse of the km/h-to-mph factor.
What is a knot, and how does it differ from mph?
A knot is one nautical mile per hour; since a nautical mile (1,852 meters) is longer than a statute mile (1,609.344 meters), 1 knot â 1.15 mph â always somewhat faster than the same number in mph.
Why do ships and planes use knots instead of mph or km/h?
Knots are directly tied to the nautical mile, which relates to degrees of latitude â a navigationally convenient unit historically and still standard in maritime and aviation contexts worldwide.
Why is meters per second used in physics instead of km/h?
m/s is the SI (International System of Units) standard for speed, making it consistent with other SI units used throughout scientific formulas and calculations, avoiding unit-conversion steps within physics problems.
What's a typical highway driving speed in each unit?
Roughly 100-120 km/h, which converts to about 62-75 mph, or about 27-33 m/s.
How fast is the speed of sound in these units?
Approximately 343 m/s at sea level and room temperature, which is about 1,235 km/h or 767 mph â though it varies with altitude and temperature.
How precise are these speed conversions?
Fully precise, using each unit's exact defined relationship, limited only by the display precision shown rather than the underlying math.
Can I convert between more than two speed units at once?
Yes â the "Quick reference" table below the main converter shows your entered value converted into every other supported speed unit simultaneously.
How fast is a typical cycling speed?
Recreational cycling is often 15-20 km/h (9-12 mph), while competitive road cyclists can sustain 30-40+ km/h (19-25+ mph) on flat terrain.
Why does wind speed matter for converting mph to knots in weather reports?
Marine and aviation weather reports commonly use knots specifically because they're the international standard for those fields â converting to mph or km/h is often needed to make wind speed intuitive for a general audience.