# How Is Speed Measured?

Measuring speed requires time (T) and a known distance (D). Using the formula distance = rate x time (D=R*T), one determines the average speed by dividing distance by time, or R = D/T. This method assumes the object being measured is already in motion.

**Determine the units**Time units are always in hours, minutes or seconds. Distance units can be either metric or imperial.

**Select a known distance based on the units chosen**Select two points, A and B, to represent the known distance. It should be long enough to make an accurate time measurement. The shorter the distance, the more precise the time measurement must be.

**Observe the object at point A, and begin timing**As the object passes point A, start measuring the time. Using second hands on a watch or stopwatch increases accuracy when using shorter distances.

**Observe the object at point B, and stop timing**Note the elapsed time the object took to travel between the two points.

**Divide the distance by the time to obtain an average speed**Using the formula R = D/T, determine the average rate of speed. This is usually expressed as distance per time unit.