Speed Converter

The units this speed converter covers

Eleven speed units sit in the two dropdowns. Pick the unit your figure is in, pick the one you want, and the converter returns the equivalent value.

• Meter/second (m/sec), the SI unit for speed
• Kilometer/hour (kph), the road unit across continental Europe
• Mile (US)/hour (mph), the road unit in the United States and the United Kingdom
• Mile (US)/minute and Mile (US)/second
• Foot/second (ft/sec) and Foot/minute (ft/min)
• Knot (int'l) and Mile (nautical)/hour
• Mach (STP)
• Speed of light (c)

How the conversion factor method works

Every conversion on this page is one multiplication. Each unit holds a fixed relationship to every other unit, so the tool multiplies your value by that factor. Going the other way, it divides by the same number. Miles per hour to kilometers per hour uses 1.609344. Kilometers per hour back to miles per hour divides by 1.609344. Nothing else changes, which is why you can check any answer by hand.

A worked mph and km/h example

Take 60 mph. Multiply by 1.609344 and you get 96.56 km/h, which is why a 60 mph US limit and a 100 km/h European limit feel close to each other. Now run it backwards. A 130 km/h motorway limit in France divided by 1.609344 comes to 80.8 mph. A 120 km/h limit works out at 74.6 mph. Those few numbers cover most highway signs a driver meets on either continent.

Speed and velocity are not the same thing

Speed is a scalar. It has size and nothing else. Velocity is a vector, so it carries a direction as well as a size. A car circling a roundabout at a steady 30 mph holds its speed and changes its velocity the whole way round. This converter handles speed, the magnitude on its own. Direction stays your problem. The distinction matters in physics classes and in any engineering work that involves acceleration.

Knots and nautical miles per hour

Both appear in the list, and they describe the same speed. One knot is one nautical mile per hour. That works out at 1.852 km/h exactly, or about 1.151 mph. Charts, marine radar and aviation instruments label the quantity either way, so having both entries saves a second guess. Pilots and sailors on both sides of the Atlantic still work in knots, even where everything else on the panel is metric.

Mach and the speed of light

Mach (STP) states a speed as a multiple of the speed of sound at standard temperature and pressure. That reference sits somewhere around 331 to 340 meters per second, depending on which standard conditions are used, so treat a Mach figure as a comparison rather than a fixed count of meters. The speed of light is firmer. Light in a vacuum moves at 299,792,458 meters per second, a value fixed by definition since 1983. It crosses one kilometer in about 3.3 microseconds.

Feet per second and feet per minute

US engineering leans on both. Ventilation designers quote duct air speed in feet per minute, and conveyor lines are specified the same way. Feet per second shows up in ballistics and in falling body problems, where gravity adds about 32.2 feet per second every second. European counterparts usually want meters per second instead, so this pair does a lot of quiet work in cross-border specifications.

Miles per minute and miles per second

These two only make sense at large scale. The International Space Station orbits at roughly 4.8 miles per second. Escape velocity from Earth is close to 7 miles per second. Written in miles per hour, those figures turn into numbers so large they stop meaning much, which is why aerospace writing switches units. The converter moves between them without you hunting for a factor.