Best Fitness Bands and Activity Trackers Reviews and Buyer's Guide

  • Very slim/lightweight
  • Interchangeable bands
  • No sleep phase tracking
Fitbit Flex Black

Fitbit Flex

Rating: 4.8
$99.95 Buy on Amazon


The Fitbit Flex is one of the most popular fitness trackers on the market today -- and for good reason. It has the perfect balance of accessibility and quality with its minimal yet customizable design and moderate price tag. When looking for an entry-level fitness band or activity tracker, the Fitbit Flex is a great choice with comprehensive features sure to impress.

Look & feel

"The Flex is minimalist, smooth, and comfortable, not to mention incredibly stylish and customizable."

The Fitbit Flex is made of two pieces: a small, bullet-shaped tracker and a smooth, rubber-like band. The tracker nestles in and out of the band fairly easily and provides the metrics tracking and five-light display; however, taking it out and putting it back in every time it needs to be charged is a bit of a troublesome inconvenience.

The band itself is slender, lightweight, and stylish. Its design is minimalistic by default, with interchangeable bands. Each comes with a small and large band, and you can choose from black, slate, navy, teal, blue, violet, pink, red, tangerine, and lime. Beyond this wide variety, Fitbit has also paired up with designer Tony Burch to produce ultra chic Flex-compatible bracelets, necklaces, and silicone bands that are guaranteed to make a fashion statement.

While the default band is comfortable and lightweight, it’s sometimes prone to sweating, especially if worn too tightly. Additionally, it gets grimy fairly quickly, as with most trackers, and requires regular cleaning to maintain that fresh out-of-the-box look; however, its minimal design and lightness made it easy to integrate into our daily wardrobes with no hassle -- small enough to not get caught on our sleeves when getting dressed, light enough to not weigh down our arm hour after hour.

The adjustable band closes with a two-tab plastic end that you push through holes on the opposite side. Although it gets easier with time, it was actually quite difficult to put on at first; however, once on, you never really have to take it off. Whether running, showering, or sleeping, the Fitbit Flex is along for the ride.

Performance & Features

  • Wireless Sync
  • Step counter
  • Calorie counter
  • Activity tracking
  • GPS
  • Water proof
  • Meal tracking
  • Sleep tracking
  • Heart rate tracking
  • Alarms
  • Caller ID
  • iOS compatible
  • Android compatible
  • Windows compatible
  •  Battery life: 7 days
"When it comes to features, the Fitbit Flex has the vital features that most users look for."

When it comes to features, the Fitbit Flex has the vital features that most users look for. It uses accelerometer technology to measure not only steps taken but also distance travelled. The display has five lights that indicate how close you are to reaching your daily goal. The goal is preset at 10,000 steps, but this is fully customizable through the web client. Every light represents 20% of your goal, and a quick double tap lights up the display to show you how close you are to completion. We found that wearing it inspired us to park a little further back in parking lots, if only to maybe reach that goal a little sooner. The excited haptic buzzing and flashing lights when your goal is reached is so strangely rewarding that you can’t help but smile when it happens.

In addition to step tracking, the Fitbit Flex also tracks your sleep. Simply trigger “Sleep Mode” by tapping rapidly 4 times. At times, triggering Sleep Mode was incredibly frustrating and difficult, but for the most part it was tolerable and got easier each time. Once activated, the band vibrates and two sleepy-looking lights flash and slowly fade out. From this point, the tracker is more sensitive to movement and will record if you are having sound or restless sleep. This sleep efficiency data can be viewed on either the app or the web client and, in theory, can be used to increase your sleep efficiency over time. To wake your Flex back up, simply (or not so simply) repeat the tapping pattern when you wake up. Although the feature is neat in theory, we found it not as reliable as we would have liked in testing. This is especially true in instances when we would sleepily forget to wake our Flex back up, only to find midday that we were in the middle of a very restless sleep.

Despite this slight inconvenience, one of our favorite features, though not exclusive to the Flex, is the silent alarm system Fitbit provides. Instead of the obnoxious chirping phone alarms we’ve all come to dread, the silent alarm can be set through the app to wake you up by vibrating the band. It results in a more effective and less jarring morning and winds up being a nice reminder to start stepping.

Fitbit claims the Flex’s battery life spans 5-7 days, and this proved true in our tests with an average charge span of 6 days. The low-power Bluetooth capabilities allowed the data to sync wirelessly from the tracker to our phones and computers without causing significant drain on either.


"The interface is intuitive, easy to use, and by far the quickest way to access and track your fitness variables throughout your day, including steps taken, distance travelled, and calories and water consumed."

When you first set up your Fitbit Flex, you enter your age, height, and weight. This allows the app to calculate your BMI and calorie goals based on the fitness information you also provide. The set up process is quick and easy, and you’ll find yourself ready to start stepping in no time. Through the web-based interface, you can adjust your various goals, which are automatically synced to the mobile app.

For tracking on the go, the Fitbit Flex uses the classic Fitbit app that loyalists know and love. The interface is intuitive, easy to use, and by far the quickest way to access and track your fitness variables throughout your day, including steps taken, distance travelled, and calories and water consumed. The app allows you to manually enter your water and calorie intake, which helps you to monitor your net calories for the day. Even though the Fitbit database of nutritional information is lacking somewhat, it is compatible with multiple comprehensive calorie monitoring apps, such as the ever-popular MyFitnessPal. This proves to be a very powerful combination for anyone trying to monitor their weight.

The tracker itself doesn’t have GPS capabilities, but you can use the GPS settings on your phone to monitor runs through the app; however, this can cause significant phone battery drain. Even without GPS, you can count on quick and accurate step counts between your Flex and the app. It’s worth noting that even though the Fitbit Flex is fairly accurate, it doesn’t necessarily have to be. Because the majority of progress tracking is done with the two-tap “percentage complete” display, we found that we would usually view our progress in rough percentages throughout the day. So in this case, its high day-to-day consistency was ultimately more important than its accuracy, as we were able to strive to take more steps using the five-light display alone and adjust our goals as we reached them to further challenge ourselves.

To have the complete Fitbit experience, it’s worth looking into purchasing the Fitbit Aria scale, which uses the same information you enter on the web client to display your BMI and body fat percentage. The scale’s data then syncs with your other metrics to display even more comprehensive charts and graphs showing your trends and fitness progress. Although not completely necessary, the Aria scale is a great value that can add an extra layer of motivation to your fitness goals.

Final Thoughts

Rating: 4.8
  • Very slim/lightweight
  • Interchangeable bands
  • No sleep phase tracking

The Fitbit Flex is essentially the iPhone of fitness trackers: well-designed, intuitive, and more than functional enough for the majority of users. Although the features in the Fitbit Flex aren’t as comprehensive as others in the Fitbit line such as the Charge HR or the Surge, this entry-level activity tracker is more than sufficient for tracking steps, counting calories when paired with a supplementary app, and monitoring overall progress of fitness goals. Simply wearing the Flex creates a great source of motivation to be more active and take a few extra steps toward fitness each day.

$99.95 Buy on Amazon