Speed Converter

Speed units vary by region and field. Road speeds use km/h in most countries and mph in the United States and UK. Aviation and maritime navigation use knots. Physics problems typically use m/s. Converting between them manually requires remembering non-round conversion factors that are easy to get wrong. This converter takes any speed in any of the five common units and shows all five equivalents at once. The conversion goes through m/s as an intermediate step, using the exact SI-defined factors. Knots are nautical miles per hour, where one nautical mile equals exactly 1,852 meters. At 1 knot, a vessel covers 1.852 km/h or 1.151 mph.

• Driving speed conversion: US speed limits in mph do not translate easily to km/h for international drivers. Enter the limit in mph to see the km/h equivalent for any GPS or speedometer calibrated differently.
• Aviation and flight planning: Aircraft speeds are reported in knots. Convert to km/h or mph for passengers, or to m/s for aerodynamic calculations.
• Maritime and sailing: Boat speeds in knots versus wind speeds in km/h or mph. The converter shows all equivalents at once for planning and reporting.
• Physics and engineering: Equations of motion use m/s as the SI standard. Convert any real-world speed to m/s before plugging into physics formulas.

1. 1Enter the speed value you want to convert.
2. 2Select the unit that value is in.
3. 3The calculator multiplies by the unit's m/s factor to get the speed in m/s.
4. 4It then divides by each other unit's factor to get all equivalents.
5. 5All five unit values are displayed simultaneously.

• Confusing km/h and m/s: 100 km/h is about 27.8 m/s, not 100 m/s. m/s values are always smaller than km/h values by a factor of 3.6. A physics formula expecting m/s will give wrong answers if fed km/h.
• Thinking 1 knot ≈ 1 mph: 1 knot = 1.15078 mph, not 1 mph. The difference is about 15% and matters for navigation and fuel planning.
• Using mph when mph (UK) = mph (US): The statute mile used in mph is the same in the US and UK. There is no distinction between US mph and UK mph.
• Forgetting that speed limits are maximums: When converting posted speed limits, the converted value is also a maximum. A 60 mph limit converts to 96.56 km/h, not 100 km/h. Never round up for legal speed limits.

• Quick km/h to mph approximation: Multiply km/h by 0.6 for a fast mental estimate. 100 km/h × 0.6 = 60 mph (actual: 62.1 mph). Good enough for planning, but use the exact result for navigation.
• Convert once, use all five: The calculator shows all five units simultaneously. No need to run the conversion multiple times for different units.
• Use m/s for physics calculations: Kinetic energy (0.5mv²), momentum (mv), and acceleration formulas all expect m/s. Always convert to m/s first for physics problems.
• Knots rule in aviation and maritime: Air traffic control, weather reports (wind speed), and nautical charts use knots as the primary unit. Keep the knot result handy for any aviation or sailing context.