Fitbit Flex 2 v Fitbit Charge 2: Which fitness tracker is best for you?

The second generation goes head to head
Wareable is reader-powered. If you click through using links on the site, we may earn an affiliate commission. Learn more

Fitbit went on somewhat of a fitness tracker release surge last year, dropping four models for the activity conscious to strap onto their wrists. It hasn't stopped this year either, releasing the Alta HR and issuing a beefy upgrade to the Fibit Blaze. With such a range of choice being offered, though, it can be a challenge to figure out which deserves a place in your everyday life.

Coming soon: The Fitbit smartwatch

That's why we're here to take a deep-dive into what the Flex 2 and Charge 2, two of Fitbit's sequel lines, are capable of and how they stack up against each other. Here's an in-depth comparison of the two side by side.

Flex 2 vs Charge 2: Design and comfort

Fitbit Flex 2 v Fitbit Charge 2: Which fitness tracker is best for you?

The first noticeable design difference between this duo is the display— or lack thereof on the Flex 2. While the Charge 2 offers a black and white OLED screen, the Flex offers a more minimalist, camouflaged tracker which is handy for those looking to keep things discreet.

The latter also features a more secure clasp mechanism, as opposed to the fiddly design of the Charge — something which has been a criticism of many other previous Fitbit bands, too. While this can make it a tad more difficult to get on and off your wrist, it's more attractive than having a device on your arm that always feels slightly too loose.

And despite the Flex's lack of user interaction and lesser capabilities, this can actually be refreshing when compared to its sibling, which is somewhat complicated to navigate. Metrics are scrolled through by tapping on the touchscreen, with a user then able to cycle through modes by pressing the side button and swiping down on the screen.

Essential reading: Fitbit Charge 2 vs Fitbit Blaze

You'll need to accept a slight learning curve if you want displayed information, something those new to the fitness tracker scene may find convoluted when compared to the Flex.

For those looking to mix up their band and wear it outside of fitness, both devices thankfully give you a plethora of options to choose from. The Flex 2 offers a Classic collection of seven bands, with more wallet-punching options including pendants and Luxe bangles in silver, gold and rose gold. Charge 2 owners, meanwhile, are able to take advantage of similar Classic bands with pricier special editions coming in gunmetal, lavender and rose gold.

The design differences are pretty clear between these two devices, and for the most part you get what you'd expect. One glaring omission which will act a deal-breaker for some, though, is the surprising lack of full waterproofing on the Charge 2, while the Flex 2 is the first Fitbit product to tolerate a dip in the pool.

Flex 2 vs Charge 2: Activity tracking

Fitbit Flex 2 v Fitbit Charge 2: Which fitness tracker is best for you?

Activity tracking when wearing these devices offers the usual standard, with both capable of tracking steps, calories burned, active minutes, hourly activity and sleep through the auto-detect SmartTrack feature.

We found similar results across the board through experience, though the Charge 2 does have a tendency to overestimate steps on occasion. The Flex 2, meanwhile, matches favourably with Samsung's Gear Fit2 and Apple Watch Series 2 when it comes to this category.

So, what are the main differences? Well, the Charge 2 is able to measure your VO2 Max, which puts it on the same page as hardcore fitness brands Garmin and Polar, while, as we mentioned earlier, the Flex 2 is able to monitor your workout from the pool.

Essential guide: What is VO2 Max and why is it important?

You can wear the Flex 2 up to 50m (including in saltwater), with activity auto-tracked with duration and laps of four strokes monitored: freestyle, breaststroke, backstroke and butterfly. Though we did find that auto-tracking requires longer swimming sessions to fully grasp your swimming session.

While both the Charge 2 and Flex 2 can track sleep in the most basic sense, the Charge 2 gained some improvements since our initial review. The Charge 2 now supports Sleep Stages (though it's still rolling out at the time of writing), which allow you to see how long you spend in light, deep and REM sleep each night. Insights, found in the companion app, will use that data to deliver guidance on how you can improve your sleep, and you can even schedule bedtime reminders.

Flex 2 vs Charge 2: Heart rate and GPS

Fitbit Flex 2 v Fitbit Charge 2: Which fitness tracker is best for you?

Let's kick things off here by noting that neither of these fitness trackers has an built-in GPS. While this limits the experience somewhat, the Charge 2 actually has a leg-up here thanks to the inclusion of the ConnectedGPS feature -allowing you to sync with your phone to receive activity stats.

As far as the Flex 2 goes, the lack of any GPS results in more basic metrics, such as exercise duration and calories burned. With more entry-level data on display and no smartphone support to lean on, you're also more likely to encounter minor accuracy issues.

Unfortunately, the Flex also fails to pick up the slack in the heart rate monitor department. While the Charge 2 has heart-rate tracking built in, using Fitbit's PurePulse tech for continuous monitoring, those donning the Flex won't have any beat information to view.

The Charge 2 uses ConnectedGPS and its ability to track VO2 Max to give you your Cardio Fitness Level, so you can see how you compare to other people the same gender and age. You can even see how you compare to professional athletes for inspiration and/or awe at their abilities.

Further, the Charge 2 uses its abilities, and its display, to give you Relax guided breathing. All you have to do is follow the onscreen prompts to inhale and exhale.

Flex 2 vs Charge 2: Battery life

With these two devices offering different capabilities, you might expect the battery life between the pair to also vary, but this isn't exactly the case.

Fitbit pegs battery life for both devices at five days, which is slightly underwhelming. Despite this all being relative to how you use the tracker, the company's assessment for the screen-less Flex 2 is pretty much accurate. If you turn off notifications and only use it for activity tracking you can get potentially get up to nine days.

Related: What Fitbit should you buy?

As far as the Charge 2 specifics go, a five-day life is disappointing because it shows no progression from older Charge models — ones which offered much smaller screens. Using it with all notifications turned on and with heart rate tracking, sleep tracking and general daily usage, we found it possible to get about six days of life out of the Charge 2. And after charging it for around 15-20 minutes, it can last another six days.

This quick charge time is helpful, but it wouldn't hurt both devices if a lengthier battery life was available.

Flex 2 vs Charge 2: Notifications

Fitbit Flex 2 v Fitbit Charge 2: Which fitness tracker is best for you?

With both fronting primarily as fitness trackers, notification support is always going to receive a backseat — these aren't smartwatches and nor do they try to be.

When the Charge 2 is connected to your phone, you'll receive call, text and calendar notifications, but find yourself unable to reply or review them. Other notifications you'll see include reminders to move, with WhatsApp support now also available for Android phones.

Oh, and if you need to block notifications for a little bit you can. Just press and hold the button from the main watch face to mute them. You can do the same to un-mute them. There's even a Do Not Disturb mode in the settings.

Read: Fitbit Flex 2 essential tips and tricks

The Flex works a little differently, and like most other screen-free trackers uses LED lights for you to pick up on the same notifications. Fitbit has a pattern of lights and vibrations to help you differentiate between calls, texts, silent alarms, reminders to move and daily goal progress, but the lack of third-party notifications recognition is frustrating.

The bottom line: you're still going to be looking at your phone to deal with notifications and further details on your progress with both devices.

Flex 2 vs Charge 2: Price

Fitbit's Flex 2 is reasonably affordable at , considering the features, and while not as advanced as the Charge in some respects, still includes waterproofing, notification support and versatile activity tracking.

The Charge 2, priced at , is more expensive than its sibling, but attractively offered at a similar price to the Fitbit Charge HR and original Charge when they initially launched.

Flex 2 vs Charge 2: Verdict

There's a fairly clear line between who these two fitness trackers are aimed at. Quite simply, if you're looking to join the Fitbit train and want a tracker that will look nice on your wrist and get you in on the ground floor, the Flex 2 is an attractive option with very handy waterproof support.

The Charge 2 wins out for those who prioritise more detailed metrics, such as VO2 Max data, sleep tracking, GPS support, and heart rate tracking. Whether you value the Charge's upgrades enough to hand over the extra cash is down to you.

How we test

Conor Allison


Conor moved to Wareable Media Group in 2017, initially covering all the latest developments in smartwatches, fitness trackers, and VR. He made a name for himself writing about trying out translation earbuds on a first date and cycling with a wearable airbag, as well as covering the industry’s latest releases.

Following a stint as Reviews Editor at Pocket-lint, Conor returned to Wareable Media Group in 2022 as Editor-at-Large. Conor has become a wearables expert, and helps people get more from their wearable tech, via Wareable's considerable how-to-based guides. 

He has also contributed to British GQ, Wired, Metro, The Independent, and The Mirror. 

Related stories