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Body Mass Index (BMI)

Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, and Sonia Rahmati Clayton, PhD.
Body Mass Index (BMI)

© Sanguis.

  • Grades:
  • 3-5 6-8
  • Length: Variable

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Students investigate how Body Mass Index (BMI) values are calculated, and how the information can be used in research.

As part of this activity, students visit the PowerPlay exhibit at the Children's Museum of Houston. This lesson is best conducted after going to the Museum.

This activity is from the PowerPlay Teacher's Guide. Although it is most appropriate for use with students in grades 3-7, the lessons are easily adaptable for other grade levels.

The PowerPlay project is a partnership between Baylor College of Medicine and the Children's Museum of Houston.

Teacher Background

During their visit to the PowerPlay exhibit, students were asked to measure their body weight and height. But accurate measurements are just one part of an investigation. The ability to interpret and make sense of the information gathered is at least as important. This skill requires careful examination and analysis of data, and a capacity to draw solid conclusions based on the evidence available.

In this activity, students will calculate body mass index (BMI), using measurements of height and weight for six different fictitious individuals. Although BMI is not a direct measure of body fatness, it is a fairly reliable indicator of a person’s fat levels, and an elevated BMI can be a sign of future health risks. BMI can be measured in children (aged 2–19), but is interpreted differently for girls and boys of different ages. In addition to calculating their own BMI, students will use data from the Centers for Disease Control and Prevention (CDC) to draw conclusions regarding obesity in the United States.

Results from the 2007–08 National Health and Nutrition Examination Survey, using measured heights and weights, indicate that approximately 17% of US children and adolescents aged 2–19 years are obese. Obese children have an increased risk of heart disease caused by high cholesterol and high blood pressure, Type 2 diabetes, asthma, sleep apnea, and social discrimination.

For additional information, see the following pages on the CDC website: “Overweight and Obesity” (cdc. gov/obesity) and “Make a Difference at Your School” (cdc. gov/healthyyouth/keystrategies/index. htm).

Note: According to the World Health Organization, health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

Objectives and Standards

Texas Essential Knowledge and Skills (TEKS) Objectives


2. B; 4. 2. A-F; 5. 2. A

  • Collect and record data by observing and measuring, using the metric system, and using descriptive words and numerals. Measure, compare, and contrast physical properties of matter, including size.

3. 4. A; 4. 4. A; 5. 4. A

  • Students know how to use a variety of tools, materials, equipment, and models to conduct science inquiry by collecting, recording and analyzing information using tools while using appropriate safety equipment.


3. 1. A; 4. 1. D,F; 5. 1. E

  • Students will recognize and explain ways to enhance and maintain health and recognize and perform behaviors that reduce health risk throughout their lifespan.

3. 11. F; 4. 11. B; 5. 9. D-E

  • The student recognizes critical-thinking, decision-making, goal-setting, and problem solving skills for making health-promoting decisions.

Materials and Setup

Materials per Student

  • CDC’s Child and Teen BMI Calculator (http://apps.nccd. cdc. gov/dnpabmi) and CDC’s Children’s BMI Tool for Schools (http://www. cdc. gov/healthyweight/assessing/bmi/childrens_bmi/tool_for_schools. html). If you do not have Internet access, see “Explore, below.”

  • Computer with Internet access

  • Student worksheets

Procedure and Extensions


Two 45 minutes class periods


  1. Ask students to define the word, “healthy. ” Follow by asking, What determines if a person is healthy? Can our weight influence our health?

  2. Divide the class into groups of four and have each group compile a list of reasons for being overweight. Every student should provide at least one reason. Record group lists on the board.


  1. Healthcare providers and scientists use a measure, called the Body Mass Index (BMI), to help determine if a person is underweight, normal weight, overweight or obese.

  2. Explain that BMI is a fairly reliable indicator of body fatness for most people.

  3. Tell students that they will need the following information to determine BMI: weight (pounds or kilograms), height (inches or centimeters), gender (male or female), and age. Students will load these data into the CDC’s Child and Teen BMI Calculator (http://apps. nccd. cdc. gov/dnpabmi) to determine the BMI for the six individuals listed on the student sheet.

  4. If you do not have Internet access, or wish to have students calculate BMI values themselves, use one of the formulas below.

    • English Units (pounds and inches): BMI = [weight / (height x height)] x 703

    • Metric Units (kilograms and meters): BMI = [weight / (height x height)]

  5. Have students calculate the BMI values as a group project or a full class activity. Be sure that students record the BMI value and the Weight Status (underweight, normal, overweight or obese) for each child.


  1. It is possible for one person to be more or less healthy than another person of the same height, weight and BMI. For example, have students discuss how the following factors might influence a person’s health.

    • Smoking

    • Eating foods high in fats

    • Exercise

    • Disease

    • Age

  2. Ask students, How were BMI values similar for the three boys and three girls listed on the student sheet? How were they different? What conclusions can you draw about the possible health of the six students, based on their BMI values?

  3. Lead a class discussion about the affects of different factors (e. g. , age, gender, genetics, level of physical activity, access to fresh and healthy foods, etc. ) on a person’s health.

  4. Instruct students to create a T-chart with factors that can lead a person to become overweight on one side and factors that promote a healthier weight on the other side.


Have students examine charts 1 and 2 on the student sheets and answer the questions below each. Discuss their answers as a class.


Calculate the average height and weight for students in the class, and ask students, either individually or working in groups, to calculate the average BMI for the class. Conduct a discussion about the results. Have students come up with list of changes that people can make in their activities or diet to help improve a BMI that falls within the range of overweight or obese.

Funded by the following grant(s)

Science Education Partnership Award, NIH

Science Education Partnership Award, NIH

Grant Number: R25RR022697