By Grant Tinsley, Ph.D.

Whether you’re trying to lose fat, gain muscle, or just stay healthy, it may help you to quantify how your body is changing over time.

Many people weigh themselves using a simple scale. While this provides you with one potentially important piece of information, it does not tell you the whole story of your body.

Body composition refers to what your body weight is actually made up of. There are many ways body composition can be described, but they all center on the idea that your total body weight can be split up into distinct entities.

As an example, your body weight could be divided into two compartments: fat mass (all the molecules of fat in your body) and fat-free mass (all non-fat molecules in your body). 

This is what many body composition assessment devices, such as at-home body fat scales, try to do. However, accurately assessing your body composition is a challenge, especially outside of specialized medical and research facilities.

Some options for monitoring your body do not focus on body fat percentage but provide other relevant metrics. For example, aspects of your body’s shape can be monitored by using a flexible tape measure or 3-dimensional body scanning.

This article will describe how you can track your own body composition at home. Four options are briefly presented: simple body weight scales, body fat scales, flexible tape measures, and 3D scanning apps for your phone. Skinfold calipers are also discussed, although these are challenging to use correctly without help from someone else.

Note: some product links in this article are Amazon affiliate links. If you make a purchase after following these links, I may earn a small commission, which helps defray the cost of this website.

The Scale

Some people fixate on the scale. Others criticize it as being useless.

As a body composition researcher, I think the truth lies somewhere between these two extremes. 

I completely agree that our body weight alone provides incomplete information.

However, your body weight is still one important piece of information about your body.

Even when we build complex models of body composition in my research laboratory, body weight is still one of the most important values we collect. 

Why is this? For body composition, the sum is equal to its parts. This simply means that all the individual components of your body we could consider individually – muscle, adipose tissue, etc. – add up to body weight.

Body weight is also easy to measure accurately, unlike many body composition variables, such as body fat percentage. Even inexpensive scales are sufficient to track changes in body weight.

With that said, I do not recommend only looking at body weight if you are trying to understand your body and how it is changing.

Some of the simple techniques that can be paired with body weight are described in the following sections of this article.

If you want to track your body weight at home, here are some good options:

In addition to looking at body weight alone, many people are familiar with body mass index or BMI. This is a simple metric that presents your weight relative to your height squared. 

BMI categories are often used to categorize someone as being in the underweight, healthy weight, overweight, or obese categories.

Body Mass Index (BMI) in kg/m2	Weight Status
Less than 18.5	Underweight
18.5 to 24.9	Healthy Weight
25.0 to 29.9	Overweight
Over 30.0	Obesity

Similar to body weight alone, this is an imperfect metric. However, it is slightly more helpful in that it considers your height, which is another important descriptor of your body.

With that said, BMI should still be viewed cautiously. While it can be useful in describing large groups or in providing a simple descriptor of your weight status, it probably isn’t wise to base your individual health decisions on this metric alone.

At-home Body Fat Scale

At-home body fat scales use a technology called bioelectrical impedance analysis (BIA).

BIA works by injecting small electrical currents into your body through electrodes that are in contact with your skin. These currents then pass through your body and are received by other electrodes. 

Based on what was injected and detected by these electrodes, the scale can estimate how easily the current flows. This information is used within an equation to estimate body composition. 

The reason that BIA can be used to estimate body composition is that electrical currents flow more easily through tissues with higher water content, such as muscle, as compared to tissues that have lower water content and higher fat content.

In most cases, the details of the equations used by specific companies are proprietary, meaning they are not shared publicly. This means that we as consumers typically have no idea how the equations were developed, who developed them, or how valid the procedures were. 

At-home body fat scales are frequently criticized, but research from our lab has shown that the accuracy of scales varies widely between devices.

While the results of all scales should be interpreted cautiously, some could provide useful information if you use them appropriately.

If you want to use an at-home body fat scale, some of the best performers from our research study are listed below.

Tape Measure

Beyond the weight of your body, the shape of your body can be an important metric that may be useful to track.

One reason this is important is that body shape can tell you something about how your body weight is distributed.

For example, those who tend to gain more fat in their midsection may see greater increases in waist circumference than those who tend to gain more fat in other locations. This is important because these individuals tend to be at a higher risk of several diseases, including type 2 diabetes and heart disease. 

Periodically measuring your waist circumference or waist-to-hip ratio (your waist circumference dividied by your hip circumference) can help you assess whether you are gaining or losing fat in your midsection.

Similar to BMI, there are some generally accepted cutoffs for what constitutes high waist circumference or waist-to-hip ratio.

	Females	Males
High waist circumference	Above 88 cm (35 inches)	Above 102 cm (40 inches)
High waist-to-hip ratio	Above 0.85	Above 0.9

Beyond this, circumferences of different body regions can be useful if you want to track changes in certain parts of your body.

For example, if you lift weights, you may be interested to see if the circumference of your arms or thighs changes over time. Seeing an increase in your upper arm circumference after several months of lifting weights could be one indicator that you might be gaining muscle in your arms.

There are also several equations that can be used to estimate body composition variables, such as body fat percentage, from one or more circumference measurements.

For example, the United States military uses equations that uses abdomen circumference (at the level of the navel) and body weight to estimate body fat percentage:

Male Body Fat % = -26.97 – (0.12 x body weight in pounds) + (1.99 x abdomen circumference in inches).

Female Body Fat % = -9.15 – (0.015 x body weight in pounds) + (1.27 x abdomen circumference in inches)

However, there may be some advantages to simply tracking how your circumferences change over time rather than calculating body fat percentage.

If you want to use a tape measure to track your circumferences, I highly recommend using a retractable tape measure with a pin lock. These features will make it much easier to perform assessments on yourself rather than requiring someone to assist you.

Here are a few examples of inexpensive tape measures with these features:

3D Scanning Phone App

For those who like the idea of taking circumference measurements but want an automated way to do this, phone-based 3D scanning is another option.

My research team has studied 3D scanning for measuring the body and estimating body composition since 2018, and we have published numerous peer-reviewed articles on this topic. 

While bulky, expensive scanners used to be the norm, phone-based scanning has gained enormous momentum in the last few years.

There are several free or paid phone apps that provide you with body measurements using your phone camera.

These require you to take a single photo, multiple photos, or rotate in front of your phone camera.

While several promising apps are being developed, here are several free options that are currently available:

What About Skinfold Calipers?

Skinfold calipers are another method commonly used to measure body composition at home.

This method involves using calipers to measure the thickness of a double layer of your skin and subcutaneous fat at several locations on the body.

The thicknesses of the individual sites can be interpreted directly or inserted into an equation to predict body composition values like body fat percentage, fat mass, and fat-free mass.

Interpreting the values directly would typically involve seeing if the thickness of certain sites, or the sum of all the sites you assess, changes over time. 

While skinfolds can be a valuable method when a well-trained individual is performing the assessments, there are some notable downsides to this method.

For the purpose of tracking your own body composition, the major downsides of skinfolds are that they are difficult to assess yourself and challening to perform accurately.

Even for someone who is trained to perform skinfold assessments, it is a challenge to correctly locate and measure body sites on your own body. Typically, you need a trainer assessor to take your skinfolds rather than you taking them yourself.

For this reason, skinfold calipers are not one of my recommended methods when you are performing assessments on yourself.

However, if you have access to a trained assessor or want to try using skinfold calipers on yourself, here are two of the highest quality calipers available:

Comparison Table

Method	Values Provided	What is Actually Being Measured?	Pros	Cons	Price
Scale	Body weight	The force of gravity acting on your body.	Most devices are accurate for assessing body weight	Does not directly provide body composition information	$15 to $35
Body Fat Scale	Body weight Body fat %* Fat Mass* Fat-Free Mass*	For weight: The force of gravity acting on your body. For body composition: how easily electrical currents travel through the internal structures of your body.	Provides information about internal composition of the body	Many scales are inaccurate	$25 to $350
Flexible Tape Measure	Circumferences Body fat %* Fat Mass* Fat-Free Mass*	The distance around certain body parts.	Provides information about how specific body parts are changing	Requires manual measurement Does not directly assess internal body components	$8 to $15
3D Scanning App	Circumferences Body fat %* Fat Mass* Fat-Free Mass*	Visual information is received by phone camera and used to construct a 3D avatar, from which the distance around certain body parts is measured.	Provides information about how specific body parts are changing Measurements provided automatically	Fewer app options available Some apps are not free Does not directly assess internal body components	Free for apps mentioned in this article.

Which Method Do You Actually Recommend?

While the previous sections of this article focused on basic descriptions of simple, at-home methods for assessing the body, I’d like to provide my recommendations for how these could actually be implemented.

The big picture perspective is that I recommend pairing regular body weight assessments with one additional simple technique. A few options are described below.

Option 1 (Simple)

Scale + Flexible Tape Measure

A simple and inexpensive option to monitor your body over time is to use the combination of a standard scale and a flexible tape measure.

These tools will provide you with an estimate of body weight and the circumference of relevant body parts.

The reason I like this option is because it is inexpensive and simple but still provides you with better information than tracking body weight alone. The circumferences can help you understand more about a change, or lack of change, in body weight. This is explained in an example later in the article.

For circumferences, I recommend tracking your waist, hips, thigh, and upper arm. If you are interested in other circumferences (e.g., chest, calf, etc.), you could assess those as well.

While there are many equations that would estimate your body fat percentage from circumference measurements, I recommend not focusing on this number and rather seeing how your circumferences change, or don’t change, over time.

When combined with body weight information, as well as your knowledge of your lifestyle habits (nutrition, exercise, sleep, etc.), circumferences can give you an idea of how your body composition might be changing.

Here is an example pairing of an inexpensive scale and flexible tape measure:

• GE Digital Bathroom Scale
• Lytown Body Measuring Tape

Option 2 (Automated)

Scale + 3D Scanning App

Using a standard body weight scale and a 3D scanning app will provide you with similar information as Option 1 (i.e., body mass and circumferences).

Some positive aspects of using a 3D scanning app instead of manual circumference measurements are that the app is quicker, provides more circumference estimates, and has been shown to be very reliable.

Some potential downsides are the need to use your phone and the inability to measure non-standard circumferences you may be interested in, or to change the exact measurement locations.

Similar to what was discussed for the flexible tape measure, I recommend focusing on the actual circumference estimates provided by the 3D scanning app rather than a body fat percentage estimate, even if this is provided.

An example of implementing this option is to use the me – three – sixty app by Size Stream, available for free in the Apple App Store or Google Play Store, along with a body mass scale, such as the GE Digital Bathroom Scale.

Options 3 and 4 (More Data)

At-home Body Fat Scale + Flexible Tape Measure or 3D Scanning App

If you are someone who wants more information, you could consider using an at-home body fat scale instead of the standard scale, while also collecting circumference measurements with either a flexible tape measure or a 3D scanning app.

In addition to body weight and circumference estimates, this would provide you with an estimate of body fat based on bioimpedance technology.

As discussed earlier in this article, the accuracy of at-home body fat scales varies widely. From our lab’s research, some of the top-performing devices could be useful if best practices are followed and the data are interpreted with caution.

In some cases, having more data makes understanding how your body is changing easier.

In other cases, when the data from different methods don’t seem to be telling the same story, it can be more frustrating. Still, understanding each method you are using, and the fact that no method is perfect, can help you make good interpretations from your data.

Here is an example pairing of these technologies:

• Omron HBF-514 Body Composition Monitor
• Lytown Body Measuring Tape
• me – three – sixty app by Size Stream (available for free in the Apple App Store or Google Play Store)

Interpreting Results

Your body composition results should be interpreted holistically, meaning that other components of your health and lifestyle – such as nutrition, exercise, sleep, and mental health – are also considered to help explain the results you are observing.

Here is a simple example:

Let’s say that you are beginning a new fitness program that incorporates weight training and some nutritional changes, such as increasing protein, fruit, and vegetable intake.

Just prior to beginning the program, you assess your body weight and circumferences using best practices. Then, you assess them again six weeks later.

Here are some examples of results you may observe and some possible interpretations.

• Findings: Your body weight, waist, and hip circumferences decrease. Your weight lifting performance also improved.
• Interpretation: You very likely lost some fat mass since your first assessment. While it is difficult to know exactly how your fat-free mass or muscle mass have changed, the improved weight training performance is a positive sign.

• Findings: Your body weight did not change, but your waist circumference decreased and upper arm circumference increased. Your weight lifting performance
• Interpretation: A decrease in waist circumference is typically a good indicator that fat loss is occurring. The lack of change in body weight, along with the increase in upper arm circumference, could mean that you have gained some muscle mass due to the exercise and nutrition changes.

• Findings: Your body weight and several circumferences increased.
• Interpretation: Your body weight and other body size metrics increased. This means that you have likely not achieved a calorie deficit in your diet but rather have, on average, consumed more calories than you expended over the measurement period. Whether the increased weight is primarily due to increased body fat, fat-free mass, or a similar contribution of both may not be certain. Depending on your goals, these results may be no problem. However, if you are trying to lose weight or fat, you could consider making some dietary changes to support those goals.

These are just a few of the possible findings and interpretations that could be made, but hopefully they are helpful in demonstrating the thought process that may help you get the most from the data you collect.

How to Take High-Quality Assessments

No matter which methods you are using to assess your body, the quality of the data you get can be maximized if you follow best practices.

These best practices fall into two major categories: 

1. performing the assessments in a consistent manner
2. ensuring your body is in a similar state each time you assess

Performing Assessments Consistently

To perform assessments in a consistent manner, it is important to:

• use the same equipment each time you assess yourself
• follow the same procedures for how you conduct the test

As an example, if you are using a flexible tape measure, it is important to measure the same locations each time. It isn’t sufficient to quickly loop the tape measure somewhere around your abdomen and call this your waist circumference. You need to choose a consistent measurement location, such as at the level of the navel (belly button), and measure this location each time you assess yourself.

Similarly, if you are using the 3D scanning app, you should have your phone propped the same way each time, ideally using a small stand or tripod. You should also be wearing the same minimal clothing and standing in the same location with the same lighting.

Even for standard scales and body fat scales, it is ideal for these to be placed in the same location on the floor to eliminate any minor differences from moving the scales.

All the steps involved in taking assessments should be followed identically each time you perform them.

This will help reduce error or “noise” in your measurements, thereby increasing the quality of the data you are getting.

Preparing Your Body for Assessment

To ensure your body is in the same state for each assessment, you should perform assessments:

• In the morning after an overnight period of fasting and resting of at least 8 hours. Fasting should include abstaining from any consumption of food, fluids, or any other substances, to the extent possible.
• After abstaining from exercise and other vigorous activities at least overnight and preferably for 24 hours or longer.
• After following your normal lifestyle habits on the previous day. That is, you should not do anything out of the ordinary the day prior to assessment, besides abstaining from exercise.
• While normally hydrated. Since it is recommended not to drink during the overnight fast, ensure you drink adequate water the day prior to your assessment, leading up to the beginning of the overnight fast.
• After voiding your bladder and, if needed, defecating. 
• While wearing the same minimal clothing (or nude).

Performing Duplicate Assessments

One more strategy that may reduce some of the “noise” in your data is to perform measurements on two separate days within a week and average those values. 

This means that, for example, if you wanted to assess your body during a given week, you may follow all recommended practices and perform your assessments on both Tuesday morning and Thursday morning.

Then, for each metric you are tracking (body weight, waist circumference, etc.), you would average the values obtained across the two days. The averaged value is what you would use as the “real” value for that week, meaning this is the value you would use when comparing future values.

This helps reduce the influence of random, day-to-day variation in your body, which is reflected in the data you obtain from your assessments.

Here is an example:

After following best practices, you use your scale and flexible tape measure to assess your body weight, waist circumference, and hip circumference on a Tuesday morning. Then, you repeat these assessments two days later on Thursday morning.

You average the values from each morning by adding them together and dividing by two.

	Assessment 1 (Tuesday)	Assessment 2 (Thursday)	Average
Body weight (kg)	75.1	75.5	75.3
Waist circumference (cm)	82.1	82.5	82.3
Hip circumference (cm)	101.0	101.2	101.1

Summary

Whether you are trying to get healthy, stay healthy, look great, or maximize your athletic performance, your body composition is one important item to consider.

The most accurate methods of body composition assessment are typically only available in certain research or medical settings.

However, there are simple at-home methods that can provide you with some helpful information about your body and how it changes over time.

Some methods you can easily perform on yourself include a simple body weight scale, flexible tape measure, 3D body scanning app, and at-home body fat scale.

If performed correctly, these techniques may help you understand your body and aid you in pursuing a healthy lifestyle.