Speed Converter — km/h to mph, kph to mph, m/s

Speed describes how far something travels in a given time. Everyday driving uses kilometers per hour (km/h) or miles per hour (mph). Physics and engineering often prefer metres per second (m/s). Aviation and marine charts use knots. This converter translates between all of these from a single input — pick a value, choose From and To units, and read the result instantly.

Supported units include km/h, mph, m/s, knots, feet per second, and Mach (speed relative to the speed of sound). Calculations run entirely in your browser; nothing is uploaded. Use it when reading foreign road signs, comparing weather forecasts, checking vehicle specs, or working through physics homework.

Most of the world posts speed limits in km/h. The United States and United Kingdom use mph instead. When you rent a car abroad or read a European spec sheet, converting between the two scales saves guesswork. The conversion is a fixed ratio — not a rough estimate.

The formula for km/h → mph:

mph = km/h × 0.621371  ·  km/h = mph × 1.609344

Common reference points: 100 km/h = 62.14 mph · 60 km/h = 37.28 mph · 120 km/h = 74.56 mph (typical European motorway limit). Note that converting a distance in kilometres is different from converting a speed in km/h — this tool handles speed values only.

To go from mph to km/h, multiply by 1.609344. US highway limits and vehicle dashboards in mph need this when you compare them with metric data or travel in countries that use km/h.

Quick anchors: 30 mph ≈ 48.3 km/h (urban US) · 55 mph ≈ 88.5 km/h · 70 mph ≈ 112.7 km/h · 100 mph = 160.93 km/h. For legal speed limits and manufacturer spec sheets, use the exact multiplier rather than mental shortcuts like dividing by two — those introduce errors that compound at higher speeds.

Metres per second is the SI base unit for speed. It appears in physics textbooks, wind-tunnel data, sprint biomechanics, and some weather services. The link to km/h is straightforward: divide km/h by 3.6, or multiply m/s by 3.6.

m/s = km/h ÷ 3.6  ·  km/h = m/s × 3.6  ·  mph = m/s × 2.23694

Examples: 100 km/h = 27.78 m/s · 10 m/s = 36 km/h · 20 m/s = 72 km/h. To convert m/s to mph, multiply by 2.23694. To convert mph to m/s, multiply by 0.44704. Lab reports and exam answers benefit from exact factors rather than rounded intermediates.

A knot is one nautical mile per hour. Aviation and marine navigation rely on knots because nautical miles align with latitude on charts. One knot = 1.852 km/h = 1.15078 mph. Select Knot in either dropdown to compare cruise airspeed with road speed limits or to read METAR wind reports.

Mach expresses speed as a fraction of the speed of sound, which varies with altitude and temperature but is roughly 343 m/s (about 1,235 km/h or 767 mph) at sea level. Mach 1 is the sound barrier; supersonic aircraft and missile specs often quote Mach rather than km/h.

Weather forecasts report wind in m/s, km/h, mph, or knots depending on the country. Converting between them lets you compare a US mph gust with a European km/h bulletin. The Beaufort scale maps qualitative wind descriptions to speed ranges — this converter handles the underlying linear units.

Runners think in pace (minutes per kilometre or mile) rather than average speed, but the two are linked. Six minutes per kilometre equals 10 km/h; five minutes per mile equals 12 mph. Enter your average speed here if you already know it in km/h or mph.

Cyclists switch between km/h on European cycle computers and mph on US trainer displays. Leisure cycling typically sits around 15–25 km/h (9–16 mph); competitive road racers exceed 40 km/h (25 mph) on flat terrain. Converting between units helps when comparing training data across devices or regions.

This tool converts physical motion speed — how fast an object or vehicle travels through space. It does not convert data transfer rates (Mbps, Gbps), network bandwidth, or internet latency — those measure bits per second, not distance over time. Likewise, RPM-to-road-speed gearing, torque (kW to N·m), and wind pressure (psi) use different formulas and belong in vehicle or physics calculators.

When converting, make sure your input is a speed value (km/h, mph, etc.), not a travel distance. 100 km/h means "one hundred kilometres each hour," which equals 62.14 mph — not the same as driving 100 km total distance.