How to Accurately Measure Your Body Fat Percentage

How to Accurately Measure Your Body Fat Percentage

So there I was, standing in front of the mirror, slightly baffled.

What would you guess my body fat percentage was?

Bodybuilders compete around 4 to 5% and look like walking anatomy charts, so I figured I must be around…7%?

Not according to my trusty multiple-point caliper test. It said 11%.

WTF? Talk about a comedown.

I was confused by that reading, though, because I couldn’t pinch more than skin anywhere on my body but was somehow still hauling around close to 20 pounds of fat?

To put that in perspective, here’s what a pound of fat looks like:

Where could I possibly have been hiding 20 of those piles of ugly, greasy flesh, exactly? And considering the effort it took to get as lean as I was, was 7% impossible to even do naturally?

Well, I went looking for answers and in this article, I’m going to share everything I’ve learned.

By the end, you’re going to know what body fat percentage is, the pros and cons of the most popular ways of measuring it, how to get an accurate estimate of your body fat percentage, and more.

What Is Body Fat Percentage?

Many people mix up the terms “body composition,” “BMI,” and “body fat percentage.”

They’re all different.

Body composition refers to an analysis of what your body is made of—skeletal muscle, fat, bones, organs, blood, water, and so on.

BMI is short for “body mass index,” which is a numeric expression of the relationship between your height and weight.

And the definition of “body fat percentage” is built right into the term–it’s simply the percentage of your weight that’s comprised of fat.

Thus, when you measure your body fat percentage, you’re determining how much of your weight is fat.

Let’s look at an example just so it’s crystal clear.

Say a person weighs 150 pounds and 15 of those pounds are fat. His body fat percentage would be 15 divided by 150, which, expressed as a percentage, is 10%.

This percentage changes if he gains or loses fat, and it also changes if he gains or loses muscle.

For example, if he sticks to a proper diet and weightlifting routine and puts on 20 pounds, and 5 of them are fat, then he now weighs 170 pounds with 20 pounds of fat.

This would be quite a change visually but not in terms of body fat percentage, which would be 20 divided by 170, or around 11%.

Let’s say he then stops lifting for a year and loses 10 pounds of muscle but doesn’t lose any fat.

Again, this would be a big change in the mirror, but his body fat percentage would still be more or less the same–around 12% (20 divided by 160).

The simple takeaway here is that your body fat percentage is a moving target that changes according to what happens with your body composition over time.

Why Body Fat Percentage > BMI

As you know, BMI is short for “body mass index,” and it represents the relationship between a person’s height and weight.

To calculate BMI, you divide your weight in kilograms and by your height in meters squared.

For example, let’s calculate my BMI based on the stats of my picture above.

First, we convert my weight and height to kilograms and meters, respectively:

184 (pounds) x 0.45 = 82.8 (kilograms)

74 (inches) x 0.025 = 1.85 (meters)

Next, we square the height measurement:

1.85 x 1.85 = 3.4225

And finally, we divide the weight by the height squared to get my BMI score:

82.8 / 3.4225 = 24.2 (BMI)

According to the BMI chart, different BMI scores correlate to different weight categories:

• Underweight = BMI of less than 18.5
• Normal weight = BMI of 18.5 to 24.9
• Overweight = BMI of 25 to 29.9
• Obese = BMI of 30 or greater

So according to the BMI measurement, I was borderline overweight…when I had veins popping off my abs.

And therein lies the problem with BMI.

While it can be useful for analyzing large populations, it’s not very helpful as a tool for assessing individual fitness—especially among people with higher-than-average muscle mass.

If you’re trying to assess your individual fitness, you’re much better off using body fat percentage.

How to Accurately Measure Your Body Fat Percentage

Measuring your body fat percentage seems simple enough, but it can leave you seriously confused.

And that’s true regardless of the method you use because, unfortunately, they all have margins of error and can spit out wildly different readings.

For example, the multiple-point caliper test had me pegged at 11% but a handheld device said 8% and a single-point caliper said 6%.

What does that mean, exactly? Are body fat tests just crap shoots, then? Is there any way to really know your body fat percentage?

Let’s find out.

Body Composition Scales and Handheld Devices

The easiest way to measure your body fat percentage is to use a scale or handheld device.

They’re quick and easy but what you gain in convenience you lose in accuracy.

These devices use a method called bioelectrical impedance analysis (BIA), which measures your body’s resistance to a light electrical current.

The science here is simple:

Muscle is great at conducting electricity because it’s more than 70% water, whereas fat is a poor conductor because it contains less water.

Theoretically, then, the fatter a body is, the more resistant it will be to an electrical current.

Makes sense, right?

Sure…it sounds plausible enough…but BIA has some serious flaws.

First, electricity travels along the path of least resistance.

This means that the current will bypass fat stores in favor of tissues that are more easily traversed.

As you can imagine, this skews readings.

Second, most scales and handhelds only use two electrodes.

This is a problem because the current can skip over entire sections of your body. For example, foot-to-foot scales can skip the whole torso and hand-to-hand devices can ignore the lower body.

Naturally, this produces wonky readings.

Third, readings can vary dramatically depending on body conditions.

BIA devices’ accuracy is further undermined by the fact that readings are influenced by various bodily factors.

For example, testing when you’re dehydrated can result in abnormally high body fat measurements, testing after you eat can result in abnormally low measurements–in one study, testing in a fed state reduced body fat levels by 4.2 percentage points–and testing post-exercise can also produce inaccurate results.

Fourth, BIA’s equations are often fundamentally flawed.

I know I’m beating a dead horse here, but there’s another major drawback that you should know about.

Turning a measurement of electrical impedance into a body fat reading requires math, and that math often spits out wrong numbers.

Companies have to take several steps to produce these equations:

1. Accurately determining the body fat measurements of a large “control” group of people.
2. Measuring the same people’s body fat with the company’s BIA device.
3. Comparing the measurements and creating an equation that predicts BIA results based on variables such as height, weight, gender, and so on.

This is a good idea in theory, but the problem lies in step #1–the method used to develop the “control” readings.

Namely, most methods used to obtain this calibration data are themselves inaccurate.

For example, a lot of companies use hydrostatic weighing for this, and studies have found that it can be off by up to 6 percentage points depending on factors like ethnicity, body weight, and hydration levels.

And those error rates are absolute, not relative (a person with 10% body fat can clock in at 16% with hydrostatic weighing).

So, what do you get when you use inherently flawed control methods to calibrate the inherently flawed readings of BIA devices?

A very poor method of measuring body fat percentage.

The Bottom Line on Bioelectrical Impedance Analysis

All told, consumer-level BIA devices pose enough risk for inaccuracy that scientists have said they simply aren’t a valid way to estimate body fat percentage.

Even the high-end commercial devices can’t guarantee accuracy.

And because these inaccuracies aren’t even consistent, BIA devices also don’t work for tracking body fat over time.

(If they were at least consistently inaccurate, you may not be able to know your actual body fat percentage but at least you could get a clear sense of how it’s changing over time.)

Body Fat Calipers and Skinfold Testing

Here’s how skinfold testing works:

You use a tool called a caliper to measure your skin’s thickness at various points on your body, add up the measurements, and plug the sum into an equation designed to estimate your body fat percentage.

Not surprisingly, there are several downsides to this method:

First, the result is heavily subject to user error.

Pinch too much skin and you’ll get a measurement that’s higher than your actual body fat percentage. Pinch too little, and you’ll get a measurement that’s too low.

Second, even if you pinch the perfect amount of skin, bad equations can still mess up the result.

One study found that skinfold testing can be off by as much as 15 percentage points, with an average error rate of 6 points.

Two other studies on skinfold testing (one of which was conducted with bodybuilders) found error rates of 3 to 5 percentage points.

That said, despite its drawbacks, calipers and skinfold testing can be a useful way to track changes in body composition over time.

More on this in a bit.

Dual-Energy X-Ray Absorptiometry (DEXA)

DEXA is certainly the most high-tech option on this list

It works by taking a full-body X-ray that’s then used to calculate body fat percentage (X-ray energy is absorbed differently by fat and fat-free tissues, which makes it possible to measure each separately).

DEXA is often referred to as the “gold standard” of body fat measurement, but research shows that it can be just as wrong as any of the other methods on this list.

One study found that DEXA can be off by up to 10 percentage points. Two others found DEXA’s error rates to be upward of 4 points.

This helps explain why many bodybuilders have been confused by DEXA scans done at their absolute leanest that range anywhere from 6 to 10%.

Here’s why DEXA isn’t as great as many people think:

1. The machines’ accuracy is affected by a number of variables, including gender, body size, body fatness, disease state, and hydration state.
2. Different machines rely on different algorithms to convert the raw data into a body fat percentage, and some are better than others.
3. The X-ray type (i.e. fan or pencil beam) affects the test’s accuracy.
4. Different machines can produce different results—even two machines made by the same manufacturer.

Unfortunately, just there’s no way to really know if the results of a DEXA scan are truly accurate.

Bod Pod

The science behind Bod Pod testing is similar to hydrostatic weighing.

You take a seat in a sealed chamber and sensors measure the amount of air that’s displaced by your body.

Then, the readings are plugged into various equations that provide you with different body composition measurements.

Well, we already know that hydrostatic weighing often yields faulty measurements, and it appears that the Bod Pod is even less accurate.

Its readings can be influenced by a many factors, including body temperature, facial hair, moisture, and even the tightness of a person’s clothing.

Given all these variables, it’s no shocker that studies have found the Bod Pod to have rather large error rates.

In one study, the test was off by up to 15 percentage points. In other research, error rates were up to 5 or 6 points.

I can also vouch for the Bod Pod’s inaccuracy.

I’ve worked with thousands of people over the last few years and have encountered dozens who were freaking out over bizarrely high Bod Pod readings (guys with abs at 20%+ body fat, for example).

Pictures and the Mirror

Low-tech may not be sexy but, ironically, this simple method of assessing body fat percentage can be just as accurate as anything else.

You’re not going to determine exact body fat percentages with just a visual assessment, of course, but you can definitely narrow it down to a tight range.

Here are two handy charts you can compare yourself to:

You’ll notice that the ever desirable six pack tends to show up around 10% body fat, and that ab/core vascularity usually starts peeking through around 8%.

Skin starts getting thin and grainy around 7% and anything below that approaches “freak” levels of leanness.

Women naturally carry more fat in their breasts, hips, thighs, and butts, so they can look as generally lean as guys but their body fat percentages will always be higher.

For example, a guy at 10% body fat looks fairly lean but a girl at 10% is ready to step on stage and compete.

You should also know that two people with the same body fat percentage can look very different depending on how much muscle they have.

For example, a 160-pound man with 10% body fat has 16 pounds of fat, while a 190-pound man with 10% body fat has only 3 more pounds of fat but a lot more muscle. And the latter will look much fitter.

Here’s a good visual of this:

Both of these guys are around 10% body fat, but the guy on the left is sporting an extra 20 to 25 pounds of muscle that his skinny fat compatriot doesn’t have.

Read: Why People Are Skinny Fat (and How to Fix It)

So visual assessments and comparisons won’t give you the nitty gritty details of your body fat percentage, but they’re all you need to get a general sense of where you’re at.

How Do You Actually Determine Your Body Fat Percentage, Then?

If you were reading closely, you’re probably wondering how researchers were able to determine the error rates of these various methods.

What was their gold standard that they were comparing these other measurements to?

Well, the answer is called 4-compartment analysis, and it’s a rather involved process that uses several tests to determine several things:

• Bone density
• Fat mass
• Muscle tissue
• Water volume

Each of these data points are gathered using a specific testing method proven to estimate it with a high amount of accuracy.

Body water, for example, is measured via deuterium dilution, bone density is measured via hydrostatic weighing (which it’s good for, despite being a subpar method of measuring body fat percentage), and so on.

The data from each of these separate tests is then manipulated mathematically in order to determine body fat percentage. And it works really well.

Now, if you have access to a team of scientists to conduct high-tech tests whenever you feel like it, then you’re in luck–you can always precisely measure your body fat percentage.

Oh you don’t? Well, that’s too bad.

Fortunately, you can do something else instead that is consistent and accurate enough to be worth your time…

The Simple & Practical Way to Measure and Track Your Body Fat Percentage

I have a simple, inexpensive, and useful system to share with you for calculating and tracking changes in your body composition.

It’s better than relying on any single method of estimating body fat percentage because it will give you a full, 360-degree view of what’s happening with your body over time.

And that’s what really matters–are you making progress toward your goals or not?

It requires just four things:

1. A caliper
2. A measuring tape
3. A scale
4. A mirror

And here’s how it works…

1. Weigh yourself every day and calculate the average every 7 to 10 days.

Our weight fluctuates frequently depending mainly on bowel movements, glycogen storage, and water retention.

This is why it’s important not to obsess over daily weigh-ins.

Averaging your weight over the course of a week or so instead gives you a much better sense of where your weight actually stands.

(To do this, just add up your daily numbers and divide them by the number of days.)

If your 7 to 10 day average is increasing, then you can rest assured you’re gaining weight. Likewise, if that average is declining, then you’re losing weight.

It’s also important to weigh yourself in a consistent manner to get the most accurate results.

Ideally, you should weigh yourself first thing in the morning (after using the bathroom and before any food or water).

2. Take caliper measurements every week.

We recall that caliper readings aren’t a reliable method for measuring body fat percentage, but they can be very useful for figuring out whether you’re losing or gaining fat.

As a general rule, if your skin is getting thicker over time, you’re getting fatter. If your skin is getting thinner, then you’re getting leaner

I’ve experimented with a lot of calipers and skinfold testing methods, and here’s the product I like most:

Here’s why I like this caliper:

• It utilizes one-site testing, which means you can do it yourself and there are fewer chances for making mistakes.
• Its body fat measurements are surprisingly accurate.

I’ve used this caliper with hundreds of people, and it rarely produces results that are wildly off base. The company says it should be accurate to within 1 to 2% with most people, and that squares with my experience.

Here’s how to use this caliper:

Take that reading every week and you’ll be set.

3. Measure your waist on a weekly basis.

Monitoring your waist size at the navel is an easy way to tell whether you’re gaining or losing fat.

All you need is a measuring tape and if your waist is expanding, you’re gaining fat. If it’s shrinking, you’re losing fat. Voila.

4. Take pictures every week.

Concrete numbers are nice, but at the end of the day, how we look in the mirror is what matters most.

When we obsess over our reflections in the mirror on a daily basis, though, it’s easy to get down on ourselves because we’re going going to miss the gradual improvements that are taking place.

That’s why it can be so helpful to take front, side, and back pictures every week (in underwear and good lighting).

These pictures will help you see progress that you might otherwise not have noticed and keep you motivated.

What’s a Healthy Body Fat Percentage for Men and Women?

We live in a culture that demonizes body fat but it’s actually essential for the human body to function properly.

It helps protect our internal organs, regulate body temperature, and produce vital hormones and chemicals, among many other roles that keep us alive and healthy.

This is why you can only get so lean before your health starts to deteriorate.

The perception of “too lean” varies from person to person, but here’s how different body fat levels are classified scientifically:

CLASSIFICATION	MEN	WOMEN
Essential Body Fat	2 – 4%	9 – 11%
Athlete	6 – 13%	14 – 20%
Fit	14 – 17%	21 – 24%
Normal	18 – 25%	25 – 31%
Overweight/Obese	26%+	32%+

As much as people want to be “shredded” these days, you simply can’t maintain a “stage-ready” level of body fat naturally without screwing up your body.

Get too lean and you’re asking for all kinds of trouble. You can mess up your hormones and organs, tank your metabolism and immune system, and battle with chronic fatigue and depression.

And to make matters worse, once you’ve done the deed, a return to normalcy can take a very long time.

That said, you can get leaner than you might think without suffering any of those consequences.

Check out the following article to get the whole picture of body fat levels and health and how lean you can get (and maintain) without screwing up your body:

The Bottom Line on How to Measure Body Fat Percentage

There’s really no way to calculate body fat percentage with 100% accuracy.

Well, I guess you could remove all the fat from your body and weigh it, but then, you know, you’d be dead.

The point is every method out there for assessing body fat percentage is an estimation. And as you’ve seen, some are better than others but none are as great as we would like to think.

Unfortunately the best option—4-compartment analysis—isn’t available to any of us, really, so we’ll have to settle for an estimated range.

Who cares, though?

The reality is body fat measurements themselves aren’t as important as how our physique is changing over time and how we ultimately want to look.

That’s why I recommend you use the simple strategy I laid out above.

They’re simple and will help you stay on top of whether your diet and workout regimens are keeping things moving in the right direction, which is what really matters in the end.

What’s your take on how to measure body fat percentage? Have anything else to share? Let me know in the comments below!

I'm Mike and I'm the creator of Muscle for Life and Legion Athletics, and I believe that EVERYONE can achieve the body of their dreams.

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