I tested a $20 smart scale against a $8,500 body composition machine – these were the surprising results

For a little over four months I’ve been using a Vitafit smart scale to keep track of my body weight. Buying one of the best smart scales is one of the easiest ways to monitor your weight and key metrics like body mass index (BMI), body fat, and more. It can give you insight into how many calories you should be eating a day to lose weight and can help track your progress over time.

I bought my Vitafit from Amazon for around $20, and I honestly wasn’t expecting much. I’ve been pleasantly surprised by its interface and features, but deep down I’ve always been resigned to the fact that it probably wasn’t all that accurate. The results are always consistent, so relative results are still helpful, but I wasn’t really under any illusion that it was a truly accurate scale.

That was until I tested it during my recent Vitafit Bathroom Scale review. When it comes to the performance of a smart scale, the only true test of its caliber is accuracy. I’m fortunate enough to live next door to a modern, well-equipped gym that’s home to an all-singing, all-dancing body composition machine, so I decided to have a bit of a showdown, and you bet I was surprised by the results.

The Tanita MC-780MA P is a £6,500 / $8,500 / AU$12,500 body composition monitor boasting Japanese-engineered precision and clinical accuracy. It delivers over 20 total body measurements (including BMI, Fat Mass, and more) nine segmental measurements (segmental body fat, etc), and more. It boasts Class III Non Automatic Weighting Instrument (NAWI) accuracy and MDD Class II-a medical device classification. Basically, it’s some of the best body composition tech on the market.

So just how well does our $20 health hero stack up to this $8,500 behemoth? I ran a series of controlled tests on the Vitafit and the Tanita to find out. I tested myself on the Vitafit, then the Tanita, and then the Vitafit again a short time later, with a short walk in between as I traveled to and from the test site. The results were a mixed bag, but overall I was blown away by how accurate the Vitafit proved in some key measurements, plenty of other figures were in the ballpark, and only a couple stood out as wild or erratic.

The pair share 11 total measurements: here’s how they stacked up.

The Vitafit came within 0.15 kg of the Tanita for body weight in both measurements. The latter lower weight reflects the energy I’d expended walking to and from my gym between the second tests.

Weight is the core metric of a smart scale and the most important number when it comes to overall health, calorie tracking, and more. I couldn’t believe the Vitafit was so close to the Tanita, a fantastic start.

I’d been suspicious of the Vitafit’s bodyfat readings, and the smart scale does indeed seem to be lacking here, which is a shame because it’s an important reading. Having high body fat can increase your risk of certain diseases, but having too little can also be dangerous. Vitafit seems to be lowballing this one, reading between 1.3-1.4% lower than the Tanita. That’s quite a significant discrepancy in a reading of around 26-27%.

Fat Free Mass is the amount of your body that’s not made up of fat, broadly your lean mass, skeleton, and more. If you’re trying to lose weight or get in shape, you ideally want to cut down the aforementioned body fat while holding onto as much FFM as possible, or even building it up through strength and resistance training.

Vitafit seems to be overegging this one, measuring 1.4-1.5kg more than the Tanita. However, that checks out when you consider it’s underestimating body fat.

Bone Mass measures the amount of minerals contained in a certain volume of bone (definition) and can be used to measure bone density, track osteoporosis treatment, and predict how likely bones are to break. Vitafit excelled here, coming within 90 grams of the Tanita measurement on both occasions, a really impressive score.

Muscle Mass is a self-explanatory reading (it’s the amount of muscle your body is carrying) and is another great metric to track if you’re trying to increase muscle mass or lose weight. Generally, as with FFM, you ideally want to hold onto as much muscle as possible (or build more) while reducing your body fat, if you’re trying to lose weight. Obviously, this will depend on your fitness goals (that maxim won’t apply to marathon runners, for instance), but tracking it can help you monitor and avoid muscle atrophy (muscle thinning or wastage).

This is a trickier comparison because Vitafit gives muscle mass as a percentage of your body weight, rather than in kilos. However, according to my calculations, it’s overestimating muscle mass by 1.3-1.4kg.

Again, this fully checks out with the discrepancy in body fat above.

Visceral fat measures the amount of belly fat in your abdominal cavity, as opposed to subcutaneous fat, which lives below your skin. A healthy amount is important to protect your organs, but too much can lead to serious health issues. Visceral fat is usually expressed simply as a number, and here Vitafit threw out one of its biggest discrepancies.

Tanita clocked me at a 10, while the Vitafit scored me a whopping 18. This is doubly annoying because the former (according to Tanita’s own scale) is healthy, while the latter is excessive. Considering that the Vitafit underestimated overall body fat, this is a further surprising result. It won’t surprise you to learn I’m going with Tanita on this one.

Body water is the total amount of fluid in your body and a key marker of dehydration. I’m sure I don’t need to expound on the benefits of drinking water to you, but it’s worth knowing that the ideal normal range for adult women is 45-60%, and for men, it’s 50-65%.

As you can see, the Vitafti is more than 5% off here, which is a worrying discrepancy considering the normal range is only a 15% margin. This is another one I’m taking with a pinch of salt (or should I say electrolytes?). The Vitafit body water measurements were identical both times as well, so this is an indication of measuring troubles rather than an anomaly.

Body Mass Index is one of the health markers you’re likely most familiar with, especially if you were ever fat-shamed by a Nintendo Wii Fit back in the day. It’s essentially your body mass divided by the square of your body height, expressed as a number. There are some limitations because it only measures overall weight rather than body composition.

For example, a hefty American Football player in great shape, but carrying a large amount of muscle, would easily score an obese rating. For the Vitafit, however, it’s another string to the bow, scoring within 0.1 of the Tanita. BMI isn’t a perfect marker of health these days, but if you need to know it you can count on Vitafit.

Basal Metabolic Rate is the number of calories your body needs to sustain itself day to day, and a vital piece of information for anyone trying to lose or gain weight, or indeed trying to sustain their current weight. There’s a discrepancy of about 200 calories between the Vitafit and the Tanita here, but because BMR is a calculation rather than a measurement, I’m going to let this one slide.

There are multiple ways to calculate BMR – the Mifflin-St Jeor equation, the Revised Harris-Benedict equation, and the Katch-McArdle Formula to name three – and Vitafit and Tanita may likely be using different formulas, which often differ by 10% in my experience.

Skeletal muscle mass makes up the muscles connected to your bones and usually comprises 30-40% of your total mass. They provide the power you need to move around and protect your joints, so having a healthy amount is a good marker of overall well-being. Expressed as a percentage, the Vitafit was 1.7% off in both instances here, it’s not a perfect measurement but it’s also not a huge discrepancy.

Your metabolic age is a comparison of your BMR versus the average for your age group. Ideally, you want a score that reflects your actual age or is lower than your actual age. The Vitafita and Tanita were worlds apart here, but I reckon there’s a good explanation. As noted, the BMR scores given by each were very different, likely reflecting different methodologies. Using the same disparate numbers to calculate Metabolic Age is likely why the Vitafit says I’m 24 while the Tanita says I’m 44.

Measuring up

As you can see, the Tanita was always going to be the clear winner when it comes to precision and accuracy, but I was really surprised by just how well the Vitafit kept up. I couldn’t believe that measurements like weight, BMI, and bone mass were so close to the heavy hitter’s readings.

Undoubtedly, this testing does reveal some of the limitations of a smart scale, and clearly, the $20 Vitafit struggles more with the composition aspect of its duties, notably for body fat, muscle mass, and water.

I’m less concerned about BMR and metabolic age because those appear to be calculations rather than measurements.

Overall, I’m thoroughly impressed with just how well my $20 smart scale held its own against an $8,500 body composition machine. If anything, this shows that splashing out a bit more on the best smart scales on the market should yield even more accurate results.

In the meantime, even the cheapest smart scale you can find will bring you some benefits in terms of tracking that can help you lose weight and stick to your fitness goals. Check out our guide on how to use a smart scale for more information on using them.

Perhaps more importantly, these results show that Vitafit the is giving out consistent measurements with each use, even if they're not always accurate. With that in mind, you can take these results with a pinch of salt and still use a smart scale like this one to great effect.