The formula for speed is speed = distance ÷ time. To work out what the units are for speed, you need to know the units for distance and time. In this example, distance is in metres (m) and time is in seconds (s), so the units will be in metres per second (m/s). Speed tells us how fast something or someone is travelling. You can find the average speed of an object if you know the distance travelled and the time it took.

Source: BBC