Speed Converter

How the speed converter works

Speed is distance divided by time, and different countries and fields express it in different units. Road signs in the United States and United Kingdom use miles per hour (mph), most of the rest of the world uses kilometers per hour (km/h), and science, engineering, and sport timing use meters per second (m/s). This converter switches between those three units. Enter a speed, type the unit you have in the From Unit box and the unit you want in the To Unit box, then press Convert. It is handy when you drive abroad, read a car or weather report, compare running or cycling paces, or check a physics problem.

Required Inputs & Typical Use Cases

• Speed

  The numeric value to convert. Decimals and negative values are accepted, and commas like 1,200 are ignored.

• From Unit and To Unit

  Type mph, km/h, or m/s. Common spellings such as kph, kmh, or mps are recognised. Using the same unit in both boxes returns the original value.

The Formula

1 mph = 1.60934 km/h       1 km/h = 0.621371 mph
1 m/s = 3.6 km/h           1 km/h = 1 / 3.6 m/s
1 m/s = 2.23694 mph        1 mph = 1 / 2.23694 m/s

• mph

  Miles per hour. One mile is 1.609344 kilometers.

• km/h

  Kilometers per hour. One kilometer is 1,000 meters.

• m/s

  Meters per second, the SI unit of speed. Multiply by 3.6 to get km/h.

Worked Example

1. Example 1: 60 mph to km/h

   60 × 1.60934 = 96.5604, which displays as 96.56 km/h.

2. Example 2: 100 km/h to mph

   100 × 0.621371 = 62.1371, so a 100 km/h limit is about 62.14 mph.

3. Example 3: 10 m/s to km/h

   10 × 3.6 = 36 km/h. A sprinter running 10 m/s is moving at 36 km/h.

4. Example 4: 90 km/h to m/s

   90 ÷ 3.6 = 25 m/s, a handy figure for highway braking distance problems.

Tips, Assumptions & Limitations

• Common mistake: multiplying when you should divide. Going from km/h to m/s divides by 3.6, because there are 3,600 seconds in an hour and 1,000 meters in a kilometer. The m/s number should be smaller than the km/h number.
• Common mistake: swapping the mph and km/h factors. A mile is longer than a kilometer, so a value in mph is always smaller than the same speed in km/h.
• Common mistake: mixing up speed units with knots. Knots are nautical miles per hour and are not supported here, so converting a nautical speed with this tool will be wrong.
• Common mistake: typing a unit the tool does not know. Use mph, km/h, or m/s; any other unit shows a friendly error rather than a wrong result.
• A quick mental estimate: mph to km/h, add about 60%. km/h to mph, multiply by 0.6.
• Results are rounded to two decimal places for display, while the calculation itself uses the full conversion factor.