Just Wondering... How Do You Measure Body Fat?

Body fat: Everyone has it, and everyone needs it. But how do you know how much you have?

Maybe you’re training for a fitness competition, you found an old pair of jeans you want to wear again, or you’re just curious about how to measure body fat for your health. Whatever the reason, it can be beneficial to know your body fat percentage.

Here’s what you need to know about measuring body fat.

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Body fat exists regardless of age, gender, or fitness level. Just like the “good” fats found in avocados, body fat is a good thing to have. Body fat essentially helps you store energy, protects your inner organs, and insulates your body (hello, inner temp control!). We’d say that’s all pretty dang important.

But there can be too much of a good thing, and that includes body fat (especially visceral fat). Higher amounts of body fat may translate to obesity and health problems, including heart disease, diabetes, and high blood pressure.

There are many formulas and calculations for measuring body fat, all of which may give you different results.

BMI (body mass index) is a numerical value of your weight in relation to your height. It’s calculated by dividing your weight in kilograms by your height in meters squared.

One problem with BMI is that it only estimates body fat. The amount of body fat could be overestimated in people with a muscular build and underestimated in older adults who have lost muscle mass. Another issue is that BMI doesn’t account for gender or age.

The Centers for Disease Control and Prevention (CDC) uses the following weight status categories for both men and women based on BMI:

Let’s use Dwayne “The Rock” Johnson as an example. The internet tells us he’s 6 feet 5 inches tall and weighs 260 pounds. If those numbers are accurate, his BMI is 30.8. According to the table above, that places him in the “obese” category.

Doesn’t seem right, does it? That’s the issue with BMI: It’s not always accurate.

Body fat percentage dives deeper than BMI and focuses on body fat in relation to the weight of your entire body. This allows you to have more insight on exactly what percentage of your body contains fat.

It’s healthy and necessary to have some body fat. If you don’t have enough, some things can go wrong.

In women, having too little body fat can lead to a medical condition called the female athlete triad. The three aspects of the triad are low energy, menstrual cycle changes (in some cases, no period at all), and low bone density.

Low body fat can affect men negatively as well. A 2013 study found that male bodybuilders whose body fat percentage decreased from 14.8 percent to 4.5 percent also experienced decreases in physical performance and immune function.

So, what’s a healthy body fat percentage? Here’s what the American Council on Exercise (ACE) has to say about body fat for men and women (although this doesn’t factor in age):

If you incorporate your sex and age, healthy body fat percentages look slightly different. Here are body fat percentages that would fall into a “normal” or “healthy” range based on sex and age:

1. Tape measure

• How it works: This is probably one of the easiest ways you can take measurements. All you need is a soft tape measure and a calculator. This method involves taking the circumference of various parts of your body to estimate body fat percentage.
• How to do it: Women should measure their neck, waist, and hips, while men need to measure only their neck and abdomen. Along with your height, input your calculations (in inches) into the following formulas to get your body fat percentage (get your calculator ready).
  Men: % body fat = 86.010 x log10(abdomen – neck) – 70.041 x log10(height) + 36.76
  Women: % body fat = 163.205 x log10(waist + hip – neck) = 97.684 x log10(height) – 78.387
• Tips: Make sure the tape measurer is comfortably placed over your skin — not so tight that it’s cutting off your circulation. Retake the measurements two or three times, and then take the average of the three results.
• Accuracy: There’s lots of room for error when you’re measuring yourself. Factors like clothing and natural bloating can also affect the results.
• Price: $. Buy a tape measure here.

2. Skinfold calipers

• How it works: Get ready to be pinched! Don’t worry — it’s painless. This process involves using calipers to measure folds of your skin on the right side of your body.
• How to do it: The skinfold sites for men are chest, thigh, and abdomen. Women should measure their triceps, thigh, and suprailium (right above the hip bone). When measuring, read the caliper to the nearest 0.5 millimeter and continue to take measurements until two of them vary by less than 1 millimeter.
• Tips: To avoid doing any math, you can use ACE’s calculator to input your measurements and get quick body fat percentage results.
• Accuracy: It can take lots of practice if you want to do this on yourself. You also need to be consistent with measurement locations to get accurate results. The downfall here is that people who carry fat in places that aren’t measured may have skewed results.
• Price: $. Buy calipers here.

3. Body fat scale

• How it works: Some high quality bathroom scales can estimate your body fat percentage using a method called bioelectrical impedance analysis (BIA). When you step on this scale, it passes an electrical current through your body (it won’t feel like you’re being electrocuted, promise!). Your body fat is resistant to electricity, so higher body fat mass translates to higher resistance to the electrical current.
• How to do it: Simple! Step on the scale and wait for the results.
• Tips: If you decide to try out a friend’s body fat scale, remember that scales made by different manufacturers may give different results.
• Accuracy: This isn’t the most accurate method. A 2016 study states that using BIA can produce reasonable results, but not when relying on a machine to calculate it.
• Price: $$. Buy a body fat scale here.

4. Air displacement plethysmography (ADP)

• How it works: This is another method that uses body mass and volume to calculate body fat composition. You sit in an enclosed device called the BOD POD, which looks kind of like an egg. Air pressure sensors measure the volume of air displaced by your body, and further calculations can then determine your body fat percentage.
• How to do it: Quick and easy — all you need to do is hang out in an egg for 3 minutes. You’ll get your results in 10 to 15 minutes.
• Tips: This is probably not the best method if you’re claustrophobic!
• Accuracy: Studies have shown this method is effective in evaluating body composition with a low range of error.
• Price: $$

5. Hydrodensitometry

• How it works: This method is also known as underwater weighing. Think about ice cubes taking up space in a glass of water — the amount of water that’s displaced by the ice cubes equals their volume. This is the same concept applied to a human in a large tub of water.
• How to do it: Since the equipment for this method is expensive, you’ll likely get the test done at a college or hospital. First you’ll be measured on land, and then you’ll be submerged in water to get your water weight. These measurements are used to calculate your body fat percentage.
• Tips: You’ll need to be comfortable wearing a bathing suit, getting in the water, and holding your breath. This method requires you to breathe out as much air as you can so that the air doesn’t add to the measurements.
• Accuracy: This is considered the most valid technique for estimating body fat percentage, but it can be challenging for some people. Some other methods are more user-friendly.
• Price: $–$$

6. 3-D body scanner

• How it works: A 3-D body scanner uses infrared sensors to get a 3-D visual of your body shape. The device then uses an equation to estimate your body fat percentage. It’s similar to circumference measurements but provides more information.
• How to do it: All you have to do is stand on a rotating platform for a few minutes. Easy-peasy!
• Tips: This isn’t the most widely available option, but a quick Google search will help you find facilities near you that offer this method.
• Accuracy: Results from this method seem to be fairly accurate, with an error rate of about 4 percent body fat.
• Price: $$-$$$

7. Body composition analyzers

• How it works: Just like body fat scales, body composition analyzers use electrical currents to assess body mass. This advanced equipment can even analyze lean and fat mass in each individual limb.
• How to do it: Step right up and allow the device to do its magic!
• Tips: Food and fluid could affect your results. Aim to do this test in the morning before breakfast.
• Accuracy: Depending on the specific device used, error rates can range from 3.8 percent to 5 percent body fat.
• Price: $–$$

8. Dual-energy X-ray absorptiometry (DEXA) scan

• How it works: This is another X-ray method used to measure body fat, lean muscle, and mineral composition. A DEXA scan machine releases lower amounts of radiation than a CT scan.
• How to do it: Instead of being fully enclosed in a machine, you’ll lie down and a large scanning arm will pass over your body to get images.
• Tips: Stay as still as possible during the scan so the images will come out clear.
• Accuracy: Experts consider this scan highly accurate and useful for tracking changes in fat and muscle over time.
• Price: $$

9. MRI or CT scans

• How it works: MRI and CT scans are typically used for other medical purposes, but they can also be great for determining the composition of our bodies! A CT scan uses computer processed X-rays to measure body fat. An MRI does the same thing minus the radiation that’s required by CT scans.
• How to do it: You’ll lie on a movable table that will slide into a long, tube-like machine. How long it takes depends on how many images are needed.
• Tips: An MRI requires spending time in a tight space. You’ll also have to stay still because movement can cause the images to become blurry.
• Accuracy: The pros of this method are that it’s accurate and it can measure specific body fat compartments. The con is that it’ll cost ya!
• Price: $$$ (CT and MRI scans can cost hundreds or even thousands of dollars.)

You need body fat to live a healthy life. If you want to know your body fat percentage, you can get answers with at-home methods or make an appointment at a medical facility or gym with specialized equipment. If your goal is weight loss, remember that healthy weight loss is a marathon, not a sprint.

Be patient and kind to yourself no matter where you are on your journey. Body fat percentage doesn’t take into consideration your best personal strengths. In the end, treating your body well is what’s important.