​How to pick the perfect smart scale

I've been asked many times about the benefits of owning a connected smart scale. The answer is quite simple -- convenience. Instead of recording your weight manually, smart scales do the job for you, syncing with various health apps so you can track your weight over time. Lots of companies make them, but how do you choose? And when does convenience become hassle?

Over the past few weeks I've been testing smart scales from Fitbit, Withings, Garmin, Under Armour and *Pivotal Living, a startup that focuses on affordable health and fitness devices.

Read: The best smart scales we've tested: Withings, Fitbit, Garmin, Eufy

Many of these connected smart scales go beyond weight and can measure metrics like body fat, bone mass and muscle mass. This is all done through bioelectrical impedance, a process that involves sending a low, safe electrical current through your body. The technology has been around for a few years. It's not the gold standard, but it generally works for measuring body measurements over time.

The drawback to using a non-smart scale is that you have to remember each measurement or write it down. This isn't the case with a connected scale or "smart" scale. These devices include Wi-Fi and Bluetooth to automatically send data to the cloud or directly to your phone. Your information can be viewed on your computer or smartphone at any time. But, there's a catch: the information generally gets funneled through specific apps.

With so many smart scales out there, it can be difficult to choose which one is right for you. That's where this guide comes in. It's an outline of what to look for and recommendations of top scales I've personally tested.

Scales I tested

• Fitbit Aria
• Withings Smart Body Analyzer
• Garmin Index Smart Scale
• Under Armour Smart Scale
• Pivotal Living Smart Scale

Smart scales tested for the buying guide.

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Features and specs

All of the scales listed above measured weight and body fat percentage and calculated body mass index (BMI). Many of them also included other features, such as measuring bone mass and muscle mass. You can view a detailed breakdown below:

How to pick a smart scale

The key to picking the perfect smart scale is to find out what it excels at and how it can fit into your lifestyle. Here are the questions you need to ask:

What can these scales do?

You first have to identify the metrics you care about. For a majority of people that will be weight, BMI and body fat. Those interested in more data may look for lean body mass, muscle mass and hydration levels, but most everyday people don't need to worry about this. I'm a data junkie and love tracking just about everything.

All of these scales support multiple users and will automatically (or at the least do their best to) recognize who is standing on it based on relative weight differences, or sometimes, local Bluetooth profiles from a person's phone. It's not foolproof, though. The scale can easily become confused if you and another user are a similar weight, but you can always manually change the profile to the correct one. The number of user profiles that can be stored range from eight to 16, which should be more than enough.

The Fitbit Aria and Under Armour scale measure weight, body fat and BMI. Garmin's scale is tailored for athletes and adds metrics such as muscle mass, body water percentage and bone mass, while the Withings Smart Body Analyzer includes air quality and heart-rate measurements.

You will also want a scale with Wi-Fi, which will automatically upload information to the cloud. Fitbit, Withings, Garmin and Under Armour all include Wi-Fi.

Is it accurate?

Almost all consumer-grade scales will have some margin of error, but you generally want one that will represent something close to your actual weight and body measurements.

Bioelectrical impedance can fluctuate based on hydration and other factors. Studies have shown that while single measurements may fluctuate, the technology is generally acceptable for determining body composition over an extended period of time. Note that if you are pregnant or have an electrical implant such as pacemaker or defibrillator you shouldn't use a scale with bioelectrical impedance.

With the exception of the Under Armour scale, I found all of the scales to be relatively accurate and consistent. Measurements didn't fluctuate by more than one or two pounds between scales over my three week testing period. The Under Armour scale, however, was highly inconsistent. Each day was a different measurement, sometimes fluctuating my weight by more than 10 pounds and body fat percentage by 9 points.

What are the apps like?

The data recorded by the scale will be synced to an app on your smartphone where you can view your weight and measurement trends over time. The challenge is, of course, that not every scale's app works the same.

The Under Armour Record app, for example, attempts to be a one stop shop for all things fitness. It supports multiple fitness trackers from different companies and can be paired with a variety of fitness and health apps. Fitbit's app, meanwhile, focuses on the Fitbit ecosystem with an added focus on nutritional tracking. Withings' app also folds in the ability to track blood pressure with a Withings connected device.

Some apps allow other scales to be connected, while others only allow one. Some connect to nutritional services, such as the MyFitnessPal app, and others don't. In short, if there is an app you use daily, you should purchase the scale that syncs with it. Own a Fitbit tracker? Buy a Fitbit Aria. Already use a Withings blood pressure monitor? The Withings Smart Body Analyzer is for you. Own a Garmin device? Then it's the Garmin Index Smart scale.

I recommend downloading the app before you purchase a device to see how you like it. Overall, I find Fitbit's app to be the easiest to navigate...but it means you're probably going to buy a Fitbit at some point, too.

You can view images of the different apps below.

Smart scale apps for Android and iOS

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Recommendations

For most people, the Fitbit Aria will be the most appealing smart scale, especially if you already own a Fitbit tracker and use the mobile app on a daily basis. The scale does the basics well and isn't too expensive. If you use either a Garmin or Withings device, however, you would be better off with one of their scales. The Withings Smart Body Analyzer is also the only scale on this list that syncs with Apple Health, which is something iPhone users should consider.

As someone who uses the Garmin Connect app daily and is an admitted data junkie, the Garmin Smart Index Scale was my favorite. The app isn't perfect, but I liked all of the extra metrics the scale was able to record. I had no problem with the Withings app, but I don't see how the CO2 and temperature measurements would aid in my weight loss.

The Under Armour scale is only available as part of a $400 HealthBox bundle. It's expensive and, due to the accuracy problems I experienced, I can't recommend it.

If you don't own a Fitbit, Withings or Garmin fitness tracker, I recommend checking out the Pivotal Living Smart Scale. It's by no means perfect, but it can measure weight, BMI, body fat percentage, basal metabolic rate and lean body mass consistently.

Amazon reviewers mentioned syncing problems and app instability as the main problems, although the scale still has a 3.7 star rating (out of 5). I didn't experience any syncing problems, but the app (as tested on a Nexus 6P running Android 6.0.1) did occasionally crash. While it has nutritional tracking built in, the Pivotal Living app also doesn't support third-party apps such as MyFitnessPal, the most popular food database. But it's a good smart scale, even better when you consider that it's a third of the price of the competition.

For now, I would avoid the Under Armour smart scale until it's offered as an individual product and some of the kinks are worked out. Otherwise, the rest of the field is grouped pretty closely across the board. Anyone already immersed in the Fitbit, Garmin or Withings "ecosystems" can feel comfortable going with those respective products.

*Editors' note (May, 22 2016): Pivotal Living has announced that it has discontinued consumer product sales and for that reason we no longer recommend the Pivotal Living Smart Scale.