Measure out a distance (d) in miles. For example, if calibrating running speed, a suitable distance would be 0.1 mile. If calibrating vehicle speed, choose a course that is a mile or more in length. A vehicle odometer can be used to measure these distances.
Complete the distance at a steady pace. Avoid accelerating or decelerating while completing the course. Use a stopwatch to measure the time (t) taken to cover the distance.
Convert the time from minutes and seconds to hours. To convert from seconds to hours, divide by 3600. To convert from minutes to hours, divide by 60. For example, a time of 42 minutes and 58 seconds = 0.72 hours = 42/60 + 58/3600.
Calculate the speed (s) of motion using the formula s = d/t. For example, a runner who covers 0.1 miles in 58 seconds is traveling at a speed of s = 6.25 MPH = 0.1 mile/0.016 h.
Change the speed of motion and repeat steps 2 to 4. Repeat this procedure until you have at least five speeds at which the same distance is covered.
Plot a reference curve on graph paper. Time (t) is plotted on the x-axis, and speed (s) is plotted on the y-axis of the graph. Let the origin of the graph be the point where t = s = 0. Plot the coordinates of each of the five speed measurements and the times associated with each speed. Use a ruler to draw a line of best fit through the five points. Note that the line does not need to pass through every point, but should rather be chosen to represent all the points. This line serves as the speed reference curve and can be used to calculate a speed in MPH when the only information available is the time taken to cover a specific distance.