How Body Fat Is Calculated [And How To Do It At Home!]

Learn how body fat is calculated, an easy way to calculate your body fat percentage at home, and why it is essential to know your number!

How Body Fat Is Calculated

Understanding Body Fat Versus Body Weight

Before we jump into how body fat is calculated and why your body fat percentage is an essential number to know, we first need to understand the difference between body fat and body weight.

The fitness and nutrition industry has detrimentally affected the health and wellness of society over the years by the constant focus on weight loss instead of fat loss and irresponsibly neglecting to clarify that they are not one and the same.

Your overall body weight, or body composition, is made up of two elements – total body fat and lean body mass (everything other than fat).

Body Composition (Total Weight) = Body Fat + Lean Body Mass

This is essential to understand when we talk about body fat – how to lose it – and shy it is not the same as body weight or rather the number that you see on a scale.

For example – as muscle weighs more than fat, someone could be leaning up by replacing visceral, disease-inducing fat with healthy, calorie-burning muscle mass and weigh the same as they did before. #ditchthescale

Someone could lose calorie-burning, structure-supporting, disease-preventing lean muscle mass and lose weight. #ditchthescale

A woman could weigh “just right” and rock washboard abs but struggle with hormonal imbalances because she doesn’t have enough body fat. #ditchthescale

A muscular man could be at a healthy body fat percentage, but due to a number on the scale be considered overweight. #ditchthescale

Here is a real-life example of the absurdity of a number on the scale as it relates to wellness or overall health.

This is Zach’s latest evaluation for our health insurance company discount. Notice that per this assessment he is “overweight”.

In case you are new around here, that is Zach. [The big one. Not the little one.]

My husband – who is clearly not “overweight”.

The point is this.

Bodyweight, rather body composition, is multi-factorial, and fat loss is very poorly reflected by a number on the scale.

Sooooooooo. . . .

. . . around these parts we are all about fat loss as it relates to body composition change which includes lean body mass or muscle.

Body Composition (Total Weight) = Body Fat + Lean Body Mass

Calculating lean body mass is sometimes necessary for medicine, but more often than not it is used by bodybuilders or those specifically interested in muscle hypertrophy as this number can be used to isolate total muscle mass.

Generally, when we talk about body composition we are talking about body fat percentage.

How Body Fat Is Calculated

Body Fat – How To Measure

This begs the question that if body fat percentage is more reflective of our overall health than a number on the scale, then how do we need to know how body fat is measured.

There are many different ways, but the simplest is to use a body fat caliper. We use this one. We haven’t owned a scale for years.

There are two methods – a 3-point site method or a 7-point site method. The 3-point method is the easiest.

Male measurement sites:

Chest: diagonal fold half the distance between the anterior axillary line and the nipple.
Abdominal: vertical fold 2cm to the right of the navel.
Thigh: midpoint of the anterior side of the upper leg between the patella and top of the thigh.

Female measurement sites:

Tricep: vertical fold at the midpoint of the posterior side of tricep between shoulder and elbow with arm relaxed at the side.
Suprailiac: diagonal fold parallel and superior to the iliac crest.
Thigh: midpoint of the anterior side of the upper leg between the patella and top of the thigh.

The video above gives an excellent demonstration of how to measure all 7 sites, but just watch how to measure the 3 sites and then you can enter your measurements into this calculator.

This is Zach’s body fat % measurements.

Once you have determined your body fat percentage find yourself on the body composition spectrum HERE and learn your disease risk factors.

How Body Fat Is Calculated

Body Composition Spectrum

Let me be very clear that this spectrum is not a gospel truth, but more so it is my assessment of the habits generally true of people at these points on the spectrum based on 15 years of medicine and a lifelong pursuit of wellness.

Stick around because we are going to break down this chart as it relates to weight loss, yoyo dieting, the coveted 6-pack, sustainable fat loss, and ultimately, the pursuit of living well.

If you are ready to pursue fat loss and body composition change, then be sure to check out my virtual 6-week fitness and nutrition program HERE! I would love to have you join my next round!