Medical-Fitness Technician
Certification Course
Part C: Assessing Medical-Fitness (LM: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.
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
Supplement: Percent Body Fat (%BF): The current position of the OptiHealth Institute in regard to body measurements and the determination of weight-related health risks is to use BMI & WHR instead of %BF. The supplemental information linked below explains the rationale of our position. The supplemental information is not a required part of this course, although it is strongly recommended that you educate yourself on this sometimes controversial topic.