A smart scale is a digital device that can measure a person’s weight and body composition to give an insight into their health and fitness. The best smart scales use bioelectrical impedance analysis (BIA), a weak electric current, that sends a painless charge through the feet to estimate a range of body metrics, including body mass index (BMI), muscle mass, protein, body fat percentage and bone density.
After measuring weight, a smart scale uses WiFi or Bluetooth (sometimes both) to send the data to your phone, where the information is stored and updated every time you step on the scales. Depending on the brand, some smart scales also measure heart rate.
Sports scientist Jamal Ramsay (opens in new tab), co-founder of JRNY supplement shakes in England, said smart scales can be beneficial because they are a budget-friendly way of measuring body composition.
“Usually, to get a body composition report, you would need to book a private health assessment or go to a specific venue, which could be quite expensive,” he told Live Science. “But with smart scales, getting these measurements is a lot easier.”
Read on to discover our tried and tested pick of the best smart scales for your home.
Best smart scales we've tested
The Renpho smart scale is one of the best smart scales we’ve tested. It’s affordable, well designed, easy to use and has an excellent app that gives real insight into the body metrics it measures.
We love how it syncs with all the main health apps (from Apple Health and Fitbit to MyFitnessPal) so it’s really simple to access your data in one place. You can measure 13 different body metrics and the app gives further insight into how these relate to the average person, in terms of being healthy or unhealthy.
Unlike most smart scales we’ve tested, the Renpho refreshingly comes with a rechargeable lithium battery and USB charger (included) rather than triple AAAs. It also has unlimited users and baby and pet modes.
But what we loved most about this device is its accuracy. Compared with professional gym scales, it put our tester at just two pounds (lbs) heavier — a close reading. We found similarly accurate results with other body metrics. Our only real complaint was that the glass on the black model smears easily and if you move it about it might need recalibrating. But if you’re looking for a budget friendly gadget that really delivers, look no further.
- Read our full Renpho smart scale review
If you’re looking for a budget-friendly smart scale that offers some bang for your buck, the Wyze Scale X is the one for you. For just $33.99, you can log 12 body metrics, resting heart rate (RHR) and access body weight trend graphs to track progress.
Looking at the stats is easy on the app: Simply tap on the different sections to see your readings, with a definition of the metric. The trouble is, there is little insight into the data, so without doing some serious Googling it’s hard to know what your results mean and how they relate to your overall health and fitness.
However, we’re big fans of the heart rate monitor feature which works with a smartphone. Put your fingertip on the rear camera lens of your phone and within a few seconds you can see your resting heart rate. This can help give an indication of cardiovascular fitness and a good place to start if you want to know how to get fit. A lower RHR can be a sign of a strong cardiovascular system.
The Wyze Scale X can serve up to eight users and has a pregnancy and weight only mode, as well as luggage, pet and baby modes. It also syncs with FitBit, Apple Health and Google Fit, making it a great value smart scale.
- Read our full Wyze Scale X review
Minimalist and budget-friendly, the Xiaomi Mi Smart Scale 2 wouldn’t be out of place in the Apple store with its hidden LED screen and smooth, rounded edges.
It’s Bluetooth-enabled, which means you need to open the companion Zepp Life app to see your 13 body composition stats. You can only see your weight on the scale itself but the app offers more insight, although some of it felt slightly clunky.
It suggests a “body age” and gives a body score out of 100, giving users a label (e.g. “good” or “poor”). It’s a fairly simple ranking but could be helpful to some people. Like most smart scales, you can view a section on how your weight and body fat has changed over time, but it doesn’t show info for the other metrics, which feels like an oversight.
Our tester also found the body type feature mildly offensive - based on your stats it puts you into a category like ‘thick set’, ‘skinny’ or ‘lacks exercise’. In simplistic terms this could be demotivating, but at worst it could be triggering for anyone with a history of disordered eating. We would also prefer a USB charger over batteries, but it’s a decent and affordable scale that gives some useful insight into health and fitness metrics.
- Read our full Xiaomi Mi Smart Scale 2 review
The Withings Body smart scale is well designed, but it only measures weight and BMI so some might see it as no different to a digital scale.
On the plus side, the Body scale is super simple to use, teams with the decent Health Mate app and works with a lot of the other main health and fitness apps too. It’s also bigger than a lot of smart scales, making it a good choice for anyone with big feet or who struggles with balance.
Disappointingly, the Withings Body scale showed wildly different readings when compared with the professional body composition scales at the gym. They also recorded our tester as 3.1 kilograms (kg) / 7 pounds (lbs) heavier than their home Renpho ones.
The Withings Body scale does everything it’s meant to do well, but it’s lacking any advanced metrics and gives no insight into body composition. If that’s what you want to track, you’re better off investing in the brand’s Body+ or Body Cardio scales instead.
- Read our full Withings Body smart scale review
Garmin watch fans might be tempted to invest $149.99 in the Index S2, the latest version of the smaller and lighter Index Smart Scale, with a new color screen, better sensors and increased body metrics. However, much as we wanted to love this smart scale, there are much better devices out there for a lot less money.
While it syncs well to the decent Garmin Connect app (and MyFitnessPal), is well designed, lightweight and easy to use, we found that for the price it was seriously lacking in some intel into the stats it records. Many smart scales have limited data on the scale but then offer a deeper dive into the meaning of metric readings in the companion app. This is not the case here. The scales and app offer the same data, with no context or explanation. The only extra you get on the app is health trend graphs.
We also found in testing there is an emphasis on multiple weigh-ins, which could be useful for pro athletes but for the average person could lead to obsessive behaviors.
There’s no doubt the Garmin Index S2 is well made and looks sleek, but it’s an expensive bit of kit that doesn’t offer enough for the price.
- Read our full Garmin Index S2 review
How do we test the best smart scales at Live Science?
All of the smart scales in this guide have been tested by our team of health and fitness writers. We evaluate accuracy and performance by comparing readings to a professional body composition reading at a gym. We also consider factors such as design, range of body composition metrics, supporting apps (including how easy they are to use and insight into data) and portability. Each smart scale is then awarded a star rating.
How do smart scales work?
Sports scientist Jamal Ramsay said that most smart scales measure body fat via bioelectrical impedance.
“Basically, they send a small current from the base of the scales throughout the body,” he said. “The current will flow freely through water and relatively freely through muscle, because muscle is around 80% water. When it hits the body fat, that current will meet resistance and that is how body fat is measured.”
The electrical charge is safe for most people, but if you have a pacemaker, medical implant or are pregnant, it’s best to speak to your doctor before you use one.
Are smart scales accurate?
Smart scales vary in accuracy but they can be a helpful way to track and understand your health and fitness — especially if you are trying to lose weight.
“Smart scales are a relatively new way of looking at a person’s weight, by looking at a lot more,” Ramsay said. “The reason why someone may want to know a bit more about their metrics is because there are some limitations to just measuring weight when on a weight loss programme that includes exercise. Muscle weighs more than fat, so an exercise program — with a healthy diet — may elicit an increase in lean muscle mass and a reduction in body fat. However, if you are looking at just your overall weight, you may not see the reductions that you expect. This can lead to inaccurate reporting of progress and a drop in motivation.”
In general, Ramsay said, smart scales provide relatively accurate body fat percentage and lean muscle mass results. Some even record your resting heart rate, which can be a good indicator of fitness.
“But there are some limitations to measuring body fat via bioelectrical impedance,” he said. “If you are dehydrated, this method will overestimate body fat. Also, these smart scales aren’t calibrated on a regular basis for accuracy, so they may get less accurate over time.”
Depending on the brand, the best smart scales can be a great way of tracking your progress. Some may be less accurate than others, and are certainly not the gold standard of measuring body composition, but the important thing to look out for is the trend.
“If you can see that your body fat or muscle mass are moving in the direction you want to on the smart scales, the likelihood is that they are, even if the results vary by a few points,” Ramsay said.