How to Estimate Your Body Fat Percentage

Knowing how much of your weight is fat helps you contextualize the number on the scale. (Image: Chaloemphon Wanitcharoentham / EyeEm/EyeEm/GettyImages)

It's all too easy to become fixated on weight as an indicator of overall fitness. But the number on the scale can't clue us in to how much of our body is fat vs. lean mass. And that's really good information to know.

Lean mass consists of bones, tissues, organs and muscle. Fat, meanwhile, is either essential or nonessential. Essential fat, stored in place like your brain, bone marrow and nerves, is what your body needs to function properly; it stores vitamins and helps you regulate your hormones and temperature. Any extra fat is considered nonessential, or "storage" fat, which is basically stored energy your body can draw from when you're low on calories.

A healthy percentage of fat for men is between 10 and 24, according to Harvard Health Publishing, while a healthy percentage for women is between 20 and 30.

If your body fat is above the recommended range, it puts you at risk for type 2 diabetes, heart disease and certain cancers, per the American Heart Association. On the other hand, if you don't have enough essential fat, your reproductive system may be impaired and it may affect the way your body uses vitamins.

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Can You Estimate Body Fat Percentage at Home?

"Many at-home scales advertise that they can measure body fat. However, they have a large margin of error," cautions Marisa Michael, RDN, CSSD, a board-certified specialist in sports dietetics in the Portland, Oregon area and owner of Real Nutrition. "Results can be skewed based on how hydrated you are, how much food you have in your stomach and whether your bowels and bladder are full."

There are several formulas out there for calculating body fat percentage, incorporating your height or weight and different body part measurements, but there isn't an agreed-upon "best" formula. What's more, while these formulas may help you roughly approximate your body fat, the math involved can be pretty confusing. For this reason, Michael says this approach is a waste of time. "It's not very accurate, so I would advise against it," she says.

A simpler tactic may be to grab a tape measure and check out LIVESTRONG.com's Body Fat Calculator. Women will need to plug in their height, as well as their neck, waist and hip measurements, while men can skip the hip measurement. Measure your waist at its narrowest point, holding the tape measure firmly, but not too tight. For women, measure your hips at their widest point, again holding the tape measure taut and parallel to the floor, but not tight. For your neck, take the measurement about an inch above where your neck meets your shoulders.

Other Ways to Measure Body Fat

There are other options out there for measuring body fat percentage that deliver more accurate results.

Bioelectric impedance: This is a method whereby an electric current is sent through the body. Based on the speed of the current (which travels fastest through water/lean tissue) and data on your height, weight, sex and age, the device calculates your estimated body fat percentage. Professional models found in physical therapy and doctor's offices are more accurate than their direct-to-consumer counterparts, but all have the same pitfall: "If you have a full stomach, bladder or bowels, the machine will read this as part of your body composition," notes Michael.

DEXA scan: A dual-energy X-ray absorptiometry (DEXA) scan was originally designed to test bone density, but it can also measure body composition. These scanners are typically found only in elite medical facilities and large university research centers. "However, most facilities that own these machines offer body composition testing for a fee," says Michael.

Air displacement plethysmography: Also known as a BodPod machine, this method looks at body volume vs. body weight. "It is considered very accurate and comparable with underwater weighing, which is the gold standard," says Michael. Looking like a big egg you sit inside, these pods are usually only found at universities and high-end sports training facilities.

Skinfold calipers: It's more common to measure body composition using this simple tool, although you'll need the help of a professional. The technician measures various sites on your body to determine the thickness of fat and skin. Accuracy depends heavily on the skill and training of the technician, as well as the quality of the calipers. It's best to find someone who is certified by the International Society for the Advancement of Kinanthropometry (ISAK). "The local Joe trainer at a big box gym will likely not have enough training to do it accurately," says Michael.

Ultrasound: Michael says she uses this device in her practice. "I have an ultrasound device in my office that I use to measure the thickness of my clients' fat and muscle tissue," she says. "It then uses height, weight, age and sex to calculate body fat percentage. This is considered very accurate."

Is Body Fat Percentage the Same as BMI?

Your body mass index (BMI) is a number used to determine if you are at a healthy weight. It's easy to use an online calculator to determine your BMI.

Remember, though, that BMI is only a ratio of your height to weight, says Michael. It doesn't indicate how much body fat you have. "If it is high, you may have excess body fat — or you may be very muscular," she says.

Rather than relying on BMI as the most meaningful health measurement, it's best to take it into consideration along with factors like your body composition, family medical history, current diet and exercise habits and lifestyle, says Michael.

Tips to Decrease Body Fat Percentage

Losing weight may or may not improve your body composition, notes Michael. It all depends on whether you're losing fat or lean mass.

In general, eating enough protein and exercising regularly, including strength exercises, is a good way to lose fat and build muscle, changing your body composition for the better, says Michael. "Talk with a sports dietitian and your doctor before making any changes. A sports dietitian can help guide you in meeting your goals in a healthful way," she adds.

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