Medical-Fitness Technician
Certification Course
Part C: Assessing Medical-Fitness
Learning Modules: 25-34
Learning Module 27-B:
Anthropometrics
Study the Learning Module and take the Quiz.
Calculating BMI & WHR
Learning Objectives:
  • Correctly determine Body Mass Index (BMI)
  • Correctly calculate Waist:Height Ratio (WHR)
1. Body Mass Index
Body Mass Index (BMI) is a calculated value that allows direct comparison among people of differing height and weight. The BMI Chart below is useful to determine a client's BMI and Healthy Weight Range without having to calculate the BMI directly.
  • First, find the client's Height in the left-hand column. Example: Client is 5' 8".
  • Then, find the client's approximate Weight in the horizontal row of the client's height. Example: 205 pounds = 203 pounds.
  • ​Finally, find the client's BMI at the top of the column of the client's approximate weight. Example: BMI = 31
  • Note the Category of the client's BMI, but be cognizant that it may need to be adjusted by the client's WHR (below).
  • As you gain experience using the chart, you will become more proficient at estimating the client's precise BMI to the first decimal. On the chart, a weight of 203 = a BMI of 31 and 210 = 32, so the client's weight of 205 would be a BMI of about 31.2.
  • BMI is recorded as a number rounded to the first decimal point and without units (no inches or pounds).
If the client's Height and/or Weight is "off-the-chart" above, use the formula below to calculate BMI.
(Wt in pounds / Ht x Ht in inches) x 703 = BMI
Install a free BMI Calculator App on your smart phone. There are several excellent versions available.
Note: Using the chart (for the majority who are in the given height range) becomes quick and easy with experience and provides the added benefit of displaying the person's healthy weight range (in the green columns for their height) and gives a sense of "context." Using a BMI App may seem quicker and easier (and works for those few who are outside the given height range), but if used exclusively, you would then lose the benefit of having the healthy weight range readily available for most of your clients.
2. Waist:Height Ratio
A person's Waist-to-Height Ratio (WHtR or WHR, but not to be confused with Waist:Hip Ratio) is defined as Waist Circumference divided by Height, both measured in the same units (inches or cm). WHR is used as a predictor of obesity-related cardiovascular and other chronic diseases, because it measures the distribution of body fat. Higher values of WHR are correlated with abdominal obesity and indicate higher health risks. A "boundary" value of 0.5 or more (one-half or more of the person's height) indicates increased risk.
Waist Circumference (inches)              .
--------------------------------------------  = WHR
Height (inches)        .
  • Use the calculator app on your smart phone to calculate your client's WHR.
  • Record the WHR as a number rounded to the second decimal point without units. Example: 32 / 68 = 0.47