Wouldn’t be nice to be able to determine your body fat percentage without the use of expensive scales, special devices, or traveling to see the doctor? Well, there is a way that it can be done with a only little bit of math and some measurements of your body. Scientists and fitness experts have developed several empirical formulas which can be used to estimate a person’s body fat percentage using a tape measure in lieu of directly measuring it. Even though these methods aren't as accurate as a water displacement test or the "bod pod", they are still a good estimate of body fat percentage. They typically only have an error of +/-3%.
For comparison, here is a table of the of body fat percentage categories.
For comparison, here is a table of the of body fat percentage categories.
Women (% fat)
|
Men (% fat)
| |
|---|---|---|
Essential Fat
|
10-13%
|
2-5%
|
Typical Athletes
|
14-20%
|
6-13%
|
Fitness (In Shape)
|
21-24%
|
14-17%
|
Acceptable
|
25-31%
|
18-25%
|
Obese
|
32%+
|
25%+
|
Source: American Council on Exercise Guidelines
Method #1: Covert Bailey Method
This method is probably the newest method available. To use this formula, you need to obtain several measurements of your body.
Women's Formula
To compute a woman's body fat percentage using this method, you will need to measure 4 different factors: A) Hips, B) Thigh, C) Calf, and D) Wrist. All measurements should be taken at their widest points and should be recorded in inches.Fat% = A+0.8B - 2C - D (for Women 30 years old or younger)Fat% = A+ B - 2C - D (for Women over age 30)Men's Formula
The measurements needed to compute body fat percentage using the Covert Bailey Method for a male are: A) Hips, B) Waist, C) Forearm Circumference, and D)Wrist. All measurements should be taken at their widest points and should be recorded in inches.Fat% = B + 0.5A - 3C - D (for Men 30 years old or younger)Fat% = B + 0.5A - 2.7C - D (for Men over age 30)For more information about this method, please refer to Covert Bailey's 1999 book called "The Ultimate Fit or Fat."
Method #2: Department of Defense Formula (aka US Navy Circumference Method)
Everyone knows that you must meet certain physical characteristics if you want to join the military. What many people don't realize is that body fat percentage is the main criteria for acceptance and not weight. When getting ready to sign up, the formula's shown below are used to determine a person's eligibility to join.
Women's Formula
To compute a woman's body fat percentage using this method, you will need to measure 5 different factors: A) Height, B) Neck Circumference, C) Waist (smallest point) and D) Hips (at the fullest point). All measurements are in inches. Note that by using this method, the waist measurement must be taken at the smallest point which is usually found halfway between the sternum and naval.Fat% = 163.205 × Log10(C + D - B) - 97.684 × Log10(A) - 78.387Men's FormulaThe measurements needed to compute body fat percentage using the Department of Defense Method for a male are: A) Height, B) Neck Circumference, and C) Waist (at navel). All measurements are in inches.Fat% = 86.01 × Log10(C - B) - 70.041 × Log10(A) + 36.76
Method #3 Heritage BMI to Body Fat Percentage Method
This method is very simplistic as the only variables needed are your age and yourBody Mass Index (which is a function of your height and weight). Please note that for people with BMI's over 30, this formula begins to overestimate body fat percentages.
Women's Formula
To compute a woman's body fat percentage using this method, you will need to know 2 different factors: A) age, B) BMI. Age should be in years.Fat% = 1.39B + 0.16A - 9If you don't want to calculate your BMI first before using this formula, then can directly calculate your body fat percentage using these variables instead: A) Age, B) Weight, and C) Height. A measurements should be in inches, lbs, and years. The modified Heritage formula becomes:
Men's Formula
To compute a man's body fat percentage using this method, you will need to know 2 different factors: A) age, B) BMI. Age should be in years.Fat% = 1.39B + 0.16A - 19.34If you don't want to calculate your BMI first before using this formula, then can directly calculate your body fat percentage using these variables instead: A) Age, B) Weight, and C) Height. A measurements should be in inches, lbs, and years. The modified Heritage formula becomes:
Method #4: YMCA Method
This method was developed by the YMCA as a simple way to estimate your body fat percentage using only your weight and your waste circumference.
Women's Formula
To compute a woman's body fat percentage using this method, you will need A)Waist Circumference, and B)Weight. All measurements are in inches and pounds.
Notice that the numerator in the above equation is the amount of fat in pounds that your body has.Men's Formula
To compute a man's body fat percentage using this method, you will need A)Waist Circumference, and B)Weight. All measurements are in inches and pounds.
Notice that the numerator in the above equation is the amount of fat in pounds that your body has.
Method #5: Modified YMCA Method
Women's Formula
To compute a woman's body fat percentage using this method, you will need to measure 5 different factors: A) Total Body Weight, B) Wrist Circumference, C) Waist (at navel), D) Hips (at the fullest point), and E) Forearm Circumference. All measurements are in inches and pounds.
Notice that the numerator in the above equation is the amount of fat in pounds that your body has.
Men's Formula
This method is easier for men because it only requires two measurements to calculate an accurate measurement of body fat. The measurements needed are: A) Total Body Weight, and B) Waist Circumference. All measurements are in inches and pounds.
The numerator in the above equation is the amount of fat in pounds that your body has. Note that this formula is nearly the same as the regular YMCA Method.
Comparison of These Methods to a Real Measurement
A couple of years ago I had a complete physical done on me. During the physical, my doctor estimated my body fat percentage to be about 26.5% using a NIR (Near Infrared Interactance) device. This machine was placed on my right bicep and measured my body fat percentage in seconds. In addition to this, I obtained measurements of my body (Weight=208lbs, Height=69in, Waist=40in, Neck=16.5in, Hips=52in, Wrist=6.5in, Forearm=11.5in) for my use. The table below shows my measured as well as my calculated body fat percentages at that point in time.
Method
|
Percentage
|
|---|---|
NIR Device
|
26.50%
|
Covert Bailey Method
|
25.00%
|
Department of Defense Method
|
25.90%
|
Heritage BMI to Body Fat Method
|
27.20%
|
YMCA Method
|
24.30%
|
Modified YMCA Method
|
26.20%
|
Average (Computational Methods)
|
25.70%
|
Range (Computational Methods)
|
24.3-27.2%
|
It's interesting to note that all of the methods are within the expected +/- 3%. The Modified YMCA Method was the most accurate for my body with the Department of Defense Method trailing close behind it. I was surprised to find that the YMCA Method was less accurate than the Heritage Method.
Which Method is Best?
It must be noted that no empirical formula is perfect.
In reality, there are many more variables that affect body fat percentage then just the simple things that are being measured for these equations. For me, the most accurate method was the Modified YMCA Method. However, most people will likely tell you that the Department of Defense Method or the YMCA Method are the most accurate. Yet others swear by Covert Bailey's method. Personally, I like to try all the methods and see what the average value and the range is. Based on that information, I can get a pretty good idea of what my body fat percentage really is. Keep in mind that all of these equations, like anything else, has some general limitations:
- These equations are generally not applicable for children or those under the age of 18
- These equations may incorrectly calculate body fat percentages for the elderly, sick, and highly athletic
Tips for Measuring your Body
Care should be taken to ensure that your measurements are taken accurately. This will help to ensure that the equations compute in the most accurate estimate of body fat percentage that is possible.
- Do not use a measuring tape that is old or stretched out.
- All measurements should be taken when the body is in a relaxed state.
- Multiple measurements should be taken and then averaged to avoid creating a large error.
- Measurements should be taken in the morning after having a full night’s rest
- Unless otherwise noted, measurements should be taken at the widest point of their specific area.
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