Stepping Science: Estimating Somebody’s Height from Their Walk

• 20 feet of straight sidewalk or a long, straight hallway
• Sidewalk chalk or two small objects to mark off 20 feet of distance
• Tape measure
• At least three volunteers to walk a short distance. They should ideally have different heights.
• Pen or pencil
• Scrap piece of paper
• Calculator

1. Find a place that has 20 feet (ft.) of straight sidewalk or find a straight hallway that is at least 20 ft. long. 
2. Using a tape measure, measure out a distance of 20 ft. and mark the beginning and ending points with a piece of sidewalk chalk (if you are using a sidewalk), or mark them each with a small object that will not be moved (if you are using an indoor hallway).

1. Measure a volunteer’s height. How tall are they? Write their height down on a scrap piece of paper. 
2. Ask the volunteer to walk from the beginning to the end of the 20 foot course you marked while counting the number of steps they take. How many steps did they take? Write down the answer.
3. Repeat this process for at least two more volunteers. How tall is each volunteer? Did they take a similar number of steps, or was there variation? Be sure to write the results down.
4. For each volunteer, figure out their step length (in feet) by dividing 20 ft. by the number of steps each took. What was the step length for each volunteer? 
5. For each volunteer, figure out their ratio of step length to height by dividing their step length by their height (both in feet). What numbers do you get for this ratio? Are they similar for the different volunteers, or is there variation? Average the step length to height ratio for all of your volunteers. Be sure to write your answers down.
6. Lastly use your results to estimate your own height. Walk from one end to the other of your 20 foot course while counting the number of steps you take. Divide 20 ft. by the number of steps you took. What was your step length? Then divide your step length by the volunteers’ average ratio of step length to height. Based on your data, what is your estimated height?
7. Have someone measure your actual height. How does your actual height compare to your estimated height? How accurate was your estimate?

Extra: Try this activity with a greater number of people. For example, you could go to a park with a jogging path or a similar location where you can ask for volunteers as they pass by. Try to collect data from at least 10 volunteers. Is there much variation in the ratio of step length to height when comparing many people? Does collecting more data make your height estimation more accurate? 

Extra: You could do this activity again but this time have volunteers walk slowly, moderately fast or very fast. How does a person’s speed affect their step length?

Extra: The human body has many other interesting ratios, such as mentioned in the Background of this activity. You could look into other ratios in the human body and come up with an activity like this one to investigate them. See the More to Explore section on the next page for relevant resources. What other ratios are consistently found in the human body from person to person?