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10 Body Comp Tools: Ranked

Here are the ten best (and worst) ways to assess body composition.

The Slow March Toward Squishiness

The process of getting out of shape is never instantaneous. Nobody wakes up suddenly overweight. It’s a slow unraveling of fitness that happens when you’re not paying attention.

So how do you pay attention? By assessing yourself on occasion.

Just don’t let those assessments turn into a downward spiral that makes you post pictures in your panties on social media, telling the world that you’re escaping the patriarchy by eating today. There’s no need to be dramatic.

Assessments are just feedback. They can show you the effects of what you’ve been doing so that you can analyze whether your fitness and nutrition are on the right track.

The Only Problem

Some assessment tools suck. They can give us widely different feedback on the same day. Other assessment tools are reliable, but impractical, expensive, or hard to find.

That’s where this rating system comes in. Let’s look at which assessment tools are crap, which are decent, and how to use them for the best results.

1. Calipers – Grade B

It’s a skinfold test. The person administering it pinches your fat at specific places on the body, then plugs those numbers into an equation to determine your body fat percentage.

There’s a 3-site, 7-site, and 9-site version, and it’s assumed that the more sites pinched, the more accurate the body fat estimation.

Where They Fall Short

  • There’s room for user error. The person pinching the skinfold can grab a lot or a little. They can pinch on the calipers harder or apply less pressure. They can also take measurements in imprecise locations.
  • Higher-quality calipers minimize user error, but they can run up to 400 bucks.
  • The locations where the skinfolds are supposed to be measured are somewhat arbitrary. As a college student, I always thanked my lucky stars nobody was measuring the skinfold on my inner thighs or the below-the-butt area.
  • It only measures subcutaneous (under the skin) fat. Visceral fat is far more dangerous. It accumulates around the heart and other vital organs but can’t be measured by calipers. Someone who has lanky arms and legs and a big hard gut might be told his body fat percentage is normal only because he carries it more around the organs than under the skin.

How to Use Them for Best Results

It’s best to have the same person administer it every time. If they’re experienced, then they’ll do it the same exact way.

Even if the measurements are imprecise, you can at least see how you’re trending over time. You could also use it to simply track the fat in specific areas. A fun thing would be to compare your abdominal fat today to your abdominal fat next month and see if it goes up or down.

2. The Scale – Grade C

This grade could be higher for certain populations. Getting a look at how heavy you are on occasion is particularly helpful for those who are very overweight, those who are very underweight, and those who don’t care about building muscle.

For those who intentionally build muscle, it needs to be taken somewhat with a grain of salt.

Where It Falls Short

  • It doesn’t differentiate between lean body mass, fat, water, or poop.
  • Lifters who have a lot of muscle can easily manipulate their weight by increasing muscle glycogen (stored energy within the muscle cells). Sometimes they do this on accident and then beat themselves up when they’re heavier or lighter than they want to be.
  • Scale weight can be higher for women during the luteal and menstrual phases because of water retention (1).
  • The power it has over people’s minds is surreal. It’s just a dang tool. You shouldn’t hate it or be a slave to it.

How to Use It for Best Results

Give yourself a range. This range might be different for you if you have more muscle than the average lifter, but as a 5’10" female, my happy range is about 152-156.

It’s on the high end when I’m going much heavier in the gym. And when it falls under 152, I lose my libido, can’t sleep, and feel cold all the time.

People who use the scale with great success generally see their weight as a byproduct of their habits and not the be-all, end-all goal.

3. DEXA – Grade A

This dual X-ray absorptiometry scan can accurately analyze your fat, muscle, and bone density.

Where It Falls Short

  • You can’t buy one for the home or casually use one at your gym. It’s somewhat inaccessible for the average person who doesn’t want to find a university or medical center where assessments are offered.
  • It’s a more expensive test ($60 to $100 a pop on average), and you’re dependent on a technician to work the machine.
  • If you get the chance to use it, it’s unlikely to be a regular thing you can do every month. Places that offer these scans recommend getting it done every 3-6 months if you’re curious about your progress. That seems like a long time to wait to see if your training plan or diet is working.

How to Use It for Best Results

If you can find one nearby and don’t mind shelling out, try it. But I wouldn’t count on it for regular assessments unless I had access to one with a discounted price. I’m cheap.

4. Bod Pod – Grade B

It’s a contraption you sit in that measures air displacement to determine what portion of your body is fat mass versus lean mass.

It’s said to be about as accurate as DEXA if you’re just wanting to measure lean mass compared to fat mass, but it won’t give you any specific info on bone density.

Where It Falls Short

  • Like the DEXA scan it can get pricey if you’re wanting to test yourself regularly, and if you’re able to find a place that offers this service, it’s subject to closing for holidays and pandemics.
  • There’s been some research showing its inaccuracy. In one study, the Bod Pod overestimated the amount of fat on lean participants by up to 13 percent and underestimated the amount of fat on heavier participants by up to almost 9 percent (2). The participants who were closest to a healthy BMI got fairly accurate results.

How to Use It for Best Results

Use it if you can, but remember that even the most respected methods can be inaccurate. And just like the other precise but expensive methods, it’s a little impractical for regular use.

5. Bioimpedance – Grade F

Bioelectrical impedance analysis (BIA), in theory, measures body fat and muscle mass via electrical currents that travel from the machine through your body.

These are the things at least one of your personal trainers has made you hold between both hands, or stand on… or both hold and stand on.

It’s intended to determine what’s fat and what’s muscle based on the areas that are storing the most water. Muscle is said to register as having a lower impedance since it holds more water. The explanation is much more complicated than this, but it doesn’t really matter since these things are known for giving hilariously inconstant readings.

Where It Falls Short

  • The same person can get different readings on different devices, or even the same device during different times of the day. While preparing for my last figure competition, I was said to be 18 percent body fat and 8 percent body fat on the same exact day. Two different bioimpedance devices were used.
  • Do you really need a second bullet point? They’re inconsistent.

How to Use It for Best Results

Maybe use it to get a laugh? Or save time and just don’t.

6. Hydrostatic Underwater Weighing – Grade A-

It’s considered the “gold standard” because of its accuracy. You basically get weighed underwater to determine what portion of your body is fat mass versus fat-free mass.

Fat-free mass (bone, muscle) has a greater density than water. Fat mass has a lower density than water; it floats. So when you’re underwater, the more lean mass you have, the more you’ll weigh.

Where It Falls Short

  • It’s inaccessible for most. I was dunked during an exercise science class but haven’t been able to “reassess” using that method again.
  • It’s kind of an ordeal. You’re not just wading gently into water. You’re sitting on a scale and getting lowered into a tank (while semi-naked) by a person you may not know.

How to Use It for Best Results

Do it if you can, but don’t depend on it as a regular assessment tool unless you have connections.

7. Mirror – Grade B+

You could obsess over the numbers all you want, but the big question is, do you look like you lift? Do you appear generally lean? The mirror answers those questions.

It’s one of the most common-sense tools we have. When you’re lean enough, you can see relatively quickly how a training method or dietary approach affects your body composition.

Where It Falls Short

  • Day-to-day changes may be so gradual that you may not realize when you’re improving or slowly getting fatter.
  • Water retention will steal your joy. So will constipation. Same with stomach distension caused by gas.
  • Posing the right way, dimming the lights, sucking in, or only looking at your best parts are all ways to deceive yourself.
  • Becoming obsessed with it is not a good look… even if you look good.

How to Use It for Best Results

Be objective. That means assessing your physique more like a scientist, not a seventh-grade bully or a woke influencer who says to love your curves.

Use it to analyze what you’ve been doing in the kitchen and gym. Remember to account for time of day (or phase of month for women), behaviors you’ve picked up recently – good or bad – and how your digestion is doing.

Try Paul Carter’s Jiggle Test if you want a more official assessment.

8. Your Favorite Jeans – Grade A

If you carry most of your weight in the hips and thighs, the fit of your best-fitting jeans will tell you a lot. If you carry your weight in the love handles, that waistband should tell you a lot too.

Where They Fall Short

  • Those who’ve disproportionately accumulated a lot of visceral fat may not get the info they need. This is likely to happen if your belly sits above your waistband.
  • Doing laundry causes shrinkage.
  • That leg-day pump will always make jeans tighter, and swelling from a workout can last a couple of days, depending on what you did.
  • They loosen up gradually with wear, so if your favorite pair is getting bigger over the years, you might assume you’re getting leaner when you’re not.

How to Use Them for Best Results

Find a pair that hug your hips, waist, and thighs without squeezing the ever-loving hell out of your body. Don’t get “stretch” jeans. They will tell you lies. And try not to put them in the dryer, like I do.

This could easily be an everyday assessment that you make on the fly. Just be aware that tighter jeans could be from spending time on the gainz-train.

9. Waist Measurements – Grade B-

If your main goal right now is to avoid heart disease and type 2 diabetes, this is the best assessment tool for you.

Here’s what the National Heart, Lung, and Blood Institute (NIH) says:

“If most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes. This risk goes up with a waist size that is greater than 35 inches for women or greater than 40 inches for men (3).”

Where They Fall Short

  • It won’t tell you crap about muscle mass, and you can’t get your body fat percentage from it.
  • There’s a bit of potential for user error. Some think their waist size is the same as the waistband on their jeans. So when their stomachs expand, and they allow their belly to flop over those waistbands, well, you can see where the inaccurate measurements come in.

How to Use Them for Best Results

Find your belly button and then measure the circumference of your waist right there. Check on this number from time to time. Do it more frequently if it’s been anywhere around these metrics: 35-inches for women, 40 for men.

The one-minute body fat test will give you even more guidance on it.

10. BMI – Grade C+

The BMI (body mass index) is a calculation or chart that shows whether you’re underweight, overweight, or normal. A BMI between 18.5 and 24.9 is said to be normal.

Oh, let me guess. You’re one of those lifters who’s only “overweight” on the BMI chart because of all that muscle you’ve built. Sure, Jan.

Sometimes you’re overweight on the BMI chart because you’re actually overweight… even if you have a significant amount of muscle.

Of course, there are outliers. Men and women with a ton of muscle can be incorrectly categorized as overweight or obese by the BMI. But they know this and are smart enough to dismiss this calculation for themselves.

Where It Falls Short

  • Since BMI is based solely on height and weight, people with lots of muscle can be incorrectly categorized as overweight.
  • It may cause the elderly who’ve lost a lot of muscle to underestimate their body fat. If they’re in the “normal” range but carrying a lot of fat and very little muscle, they’re not in good shape. But the BMI will give them the impression they are.
  • You can be categorized as normal weight but still have an unhealthy (even dangerous) amount of visceral body fat. This is particularly true if you’re kind of skinny everywhere but the belly.
  • Even if you’re in the normal range, you’ll still only have a vague idea of how much body fat and muscle you have.

How To Use It For Best Results

Recognize whether you’re truly an outlier. You’ll have a big skeletal frame and a lot of conspicuous muscle on top of it.

If you’re not, that’s okay! You may be a dedicated lifter who’s let some non-muscular pounds creep up. The sooner you can acknowledge this, the sooner you’ll be able to lean down without the excuse about how mean the BMI is to muscular people.

Final Thoughts

The key to staying generally fit as you age is just a matter of paying attention to the right things. And the biggest “right things” to be aware of are keeping muscle and limiting fat gain.

All of these tools have shortcomings, but picking out a few, keeping them in perspective, and using them fairly regularly should give you as much info as anyone would need.




  1. Tacani PM et al. Characterization of symptoms and edema distribution in premenstrual sysyndrome. Int J Womens Health. 2015;7:297–303. PMC.
  2. Lowry DW et al. **Air displacement plethysmography versus dual-energy x-ray absorptiometry in underweight, normal-weight, and overweight/obese individuals.**PLoS One. 2015 Jan 21;10(1):e0115086. PubMed.
  3. Assessing Your Weight and Health Risk. National Heart, Lung, and Blood Institute.

Thoughts about the Navy Body Fat Calculator? Allegedly accurate to within 3%-4% …

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I hadn’t heard of it before now but if the accuracy is really that close, it sounds pretty good!

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