Fitbit Charge 4 full review

Fitbit’s top activity tracker, the Charge 4 boasts a bunch of new features and functions that rival even Fitbit’s pricier fitness smartwatches. Our Fitbit Charge 4 review will look into all these fitness and health-related features, show how they work in the app, and compare it with other trackers.

The Charge 4 matches the activity tracker with the top smartwatches. In some ways, the main difference is the monochrome touchscreen.

The Charge 4 has everything the Charge 3 had and makes the tracker even better. Even owners of the excellent Fitbit Versa 2 smartwatch will look enviously at some of the new features Fitbit's tracker brings to the table.

The Charge 4 debuted Active Zone Minutes (AZM), a personalised fitness challenge that counts all activities that push your heart rate up – be that running, weights, cycling or dancing. The harder you push yourself (into Cardio and Peak zones), the more credit Fitbit gives you. This has now been rolled out to the Sense and Versa series smartwatches, and the entry-level Inspire 2 tracker.

On top of AZM, the Charge 4 comes with built-in GPS and Spotify Connect & Control – both not available on the older Charge 3. It's the cheapest Fitbit with built-in GPS too.

Best Fitbit 

The Fitbit Charge 4 is primarily a fitness tracker, but comes with other health-focused features and handy on-screen notifications, such as texts and caller ID.

In this Fitbit Charge 4 review, we’ll look at all the features (fitness, wellbeing, notifications, apps, etc), and compare it to the other Fitbits, especially the previous Charge 3 and the recent Inspire 2.

February 2021 update: The Charge 4 now has access to expanded blood oxygen data (SpO2) measurements and skin temperature tracking. And users can see seven-day trends for Breathing Rate, Heart Rate Variability, and Resting Heart Rate in the app's Health Metrics dashboard - previously available only to Premium subscribers (who do get to see 30-day trends, as well).

Fitbit Charge 4 track screens

Fitbit Charge 4 is filled with features

Starting with the basics, the Charge 4 tracks steps, distance, calories burned, hourly activity, floors climbed, heart rate, swim-tracking, and sleep.

Packed into the small tracker are a 3-axis accelerometer, optical heart rate monitor, GPS, vibration motor, NFC chip (for Fitbit Pay), altimeter, and Bluetooth LE (BLE).

Heart-rate monitoring is great for tracking calorie burn and getting real-time guidance to optimise your workouts. It is also used for advanced sleep tracking.

In addition, the Charge 4 features most of Fitbit’s more advanced functions, including Cardio Fitness Level (via three different heart-rate zones), guided breathing, move remindersauto-exercise recognition, support for exercise modes such as run, bike, swim, treadmill, weights, yoga, and circuit training; female health-tracking (track symptoms, log moods, compare cycles and more); Sleep Score, alarms, timers, calendar and weather apps; and can display notifications such as caller ID, texts, calendar, WhatsApp, and more.

Fitbit Charge 4 GPS workout intensity map

At last! GPS built-in

New to the Charge 4 (and a first on Fitbit’s non-smartwatch trackers) is built-in GPS.

Having GPS built into a tracker delivers deeper fitness and health analysis to improve your runs and cycle workouts, such as pace, rest times, speed and more.

Most Fitbit tracker wristbands allow you to connect to your phone’s GPS, but this way doesn’t always clock the correct distance travelled, as it calculates stride length to estimate this.

Now you're able to log accurate real-time pace and distance when you go running, riding or hiking, while leaving your phone at home.

There are six GPS-compatible exercise modes on the Charge 4: Run, Bike, Walk, Treadmill, Outdoor Workout, and Hike. A hike is regarded as more strenuous than a walk, and burns more calories.

Other GPS activities include downhill and cross-country skiing, kayaking and surfing.

A workout intensity map shows your GPS-monitored route, distance, achieved heart-rate zones and pace by kilometre or mile. You can tap the map to see more detailed stats about your workout as well.

GPS is set as “on” by default when you select an exercise mode, but to save battery life you can turn it off. Like most high-end Fitbits, the Charge 4 can use Run Detect and Auto Stop to work out that you are going for a run, but won’t automatically fire up the GPS.

Dynamic GPS is an optional new function that can intelligently sense if your phone is with you when you’re using the GPS tracking built into the Charge 4. If it's near, the Fitbit uses the phone’s GPS location to preserve the tracker’s battery life. 

Owners of the Versa 2 will no doubt be jealous, as that smartwatch lacked built-in GPS. The more recent Versa 3 and Sense do sport built-in GPS, too.

Fitbit Active Zone Minutes

Active Zone Minutes

Active Zone Minutes (AZM) was seen first on the Charge 4. This metric is personalised based on your resting heart rate and age. It tracks any activity that raises your heart rate - from a brisk walk to running, indoor biking and yoga. It measures the time you spend in each heart rate zone.

Fitbit measures three active heart-rate zones: starting with Fat Burn, through Cardio to Peak.

Fitbit uses your “heart-rate reserve”, which is the difference between your maximum heart rate and your resting heart rate. It’s an indication of your overall cardiovascular fitness. Your resting heart rate can be lowered by increasing your fitness level.

You can set your own goal, but the default is a weekly goal of 150 minutes (as recommended by the World Health Organization and the NHS).

AZM isn’t really that new. Fitbit has measured Active Minutes for a long time. Now, however, it has gamified the metric a little and uses the heart-rate zones in a more upfront manner. You earn one credit for each minute of moderate activity in the Fat Burn zone and two for more vigorous activity in Cardio and Peak zones.

Each time you change heart-rate zones the tracker gives you real-time alerts on your wrist, so you can push harder (or scale back) to make your workouts more efficient. You can get a detailed summary of your movement through the heart rate zones in the Fitbit mobile app.

It's a lot like Garmin's Intensity Minutes feature on its wearables.

Active Zone Minutes is now available on all Fitbit smartwatches, as well as the Charge 4 and Inspire 2. We rate it as a new motivating metric to set your goals around.

Fitbit Charge 4 Exercise Run

Keep on moving

From the clock face, you swipe up to see the Today app, which shows your daily stats (customisable), including Reminders To Move, which will prompt you to get up out of your chair and start moving for at least 250 steps per hour of the day.

Reminders to Move is a great way to make sure you don’t stay sitting for too long – and we spend over half our day sat down. It’s not just about getting your steps up and burning a few more calories. Sedentary people have up to a 49% greater risk of early death. To take two examples, sedentary behaviour leads to a 112% increase in your risk of getting Type 2 diabetes, and 147% increase in the risk of heart disease.

Fitbit Sleep Quality Tracking

Sleep monitoring, Guided Breathing and SpO2

Sleep is a key health and wellbeing indicator, and the Charge 4 gives you a Sleep Score based on detailed Time Asleep, Deep and REM sleep stages, plus 'Restoration' - the time that your sleeping heart rate is below your average waking heart rate. Only Fitbit Premium subscribers get to see Restoration data, which is a shame, but you can live without it as you get to see your overall Sleep Score regardless.

The first thing I do when I wake is to check my Sleep quality on the Fitbit app, and this is one of my favourite features. Getting a decent night's sleep is as important as hitting those 10,000 steps.

One annoyance is that my resting heart rate is very low (54bpm), and so getting below this while asleep seems more difficult for me than someone with a resting heart rate of 64-100bpm.

The tracker is light and comfortable to wear, and it won’t stop you from sleeping, unless you set the silent alarm to vibrate, of course.

The tracker now features Smart Wake, a Fitbit smartwatch feature that buzzes you during light sleep within the 30 minutes of your set alarm to wake you in a calmer way than a sudden alarm.

When not sleeping, you can still relax by using the calming Guided Breathing Sessions based on your heart rate.

Another health metric you’ll find under the Sleep section of the app is Estimated Oxygen Variation, which uses an Sp02 sensor to graph an estimation of the oxygen-level variability in your bloodstream – which can show potentially risky variations in your breathing during sleep.

Charge 4 users can now also see their blood oxygen reading on the wrist, following an update in February 2021.

Fitbit health and fitness scores and stats explained

Fitbit Charge 4 app screens

Apps and non-health functions

One of the smartest non-fitness or health-related features is Notifications. The Charge 4 will gently buzz you when you get a call on your phone (and show caller ID), text messages and pushes from the likes of WhatsApp. Android users can even send Quick Replies straight from the tracker. These can be turned on and off to your liking from both the tracker and in the mobile app.

You also get a three-day weather forecast app, set to your location. Plus a new app, Agenda, which you can sync with a calendar.

And, new to the Charge family, are Spotify controls. You can't actually store any music on this tracker, as you can with the Versa 2 smartwatch, but you can choose the music output, play, shuffle and skip content, browse recent playlists and podcasts, and even Like songs. It requires the premium Spotify subscription.

Now all models of the Charge 4 feature contactless Fitbit Pay - which works just like Apple or Google Pay. On the Charge 3, only the Special Edition had Pay. That said, the number of participating banks in the UK is still pretty pitiful.

You can set Alarms, and use the tracker as a Stopwatch or Timer.

Smart Wake lets the tracker set alarms and wake you at the best possible times depending on your sleep cycles to ensure you’re well-rested and ready to wake at an optimal time close to when you set your alarm.

The tracker comes with 24 different clock faces to choose from, although these aren’t as dynamic and colourful as the ones you can get for the Fitbit Versa and Ionic smartwatches.

Despite backlighting, the display can be difficult to read in bright sunlight and almost impossible to view with sunglasses on. Again, only the smartwatches fix this problem.

Display On Settings lets you adjust the time your Charge 4 screen remains on with each view.

Fitbit Charge 4 Classic and Special Edition

Design and straps

The Charge 4 looks very much like the Charge 3. While the Charge 3 tracker was made of aluminium, the Charge 4 tracker has a plastic resin case - so it’s even more lightweight (44g compared to 47g) despite packing more inside. The Versa 2 is 60g, so if every gram counts, the Charge 4 wins on this factor.

It has an inductive, rather than a physical button, on the left edge, which aids its water resistance (up to 50m).

To navigate to its many features, you tap, scroll and swipe the backlit 100x160 OLED touchscreen.

The tracker itself comes with both Small and Large sizes of detachable wristband – a swim-proof Classic band made from elastomer in one of three colours and the black Special Edition, which comes with a Granite Reflective Woven band, plus an extra Black Classic band.

The tracker itself can be swapped between different wristbands. For the Charge 4 these include: Sports (£19.99 / $29.95 / €29.95), Horween Leather (£59.99 / $49.95 / €69.95), Woven (£24.99 / $34.95 / €39.95), and Classic (£19.99 / $29.95 / €29.95).

The Classic and Sports bands are sweat and swim-proof, while the Woven and Leather bands are not intended for high-intensity workouts. As such, you’ll need to swap to one of the other bands when swimming or working up a sweat.

The accessory bands are available in either Small (fits wrists 5.5-7.1in or 140-180mm) or Large sizes (7.1-8.7in, 180-220mm). Fitbit has a sizing tool that you can print out to see which size fits you.

To make it easier, here are the available Charge 4 bands in all their glory. They fit both the new Charge 4 and the older Charge 3. 

Fitbit Charge 4 battery life

Battery life

The Charge 4 boasts one of Fitbit’s longest-ever battery life spans, at up to seven days - bettered only by the Inspire 2's 10 days. Compare that to the Apple Watch, which has an 18-hour battery life and usually requires an overnight charge.

Of course, battery life varies with use and other factors. Fitbit claims that it will last up to five hours with continuous GPS use. Apple says that its smartwatch lasts an hour longer with GPS use.

The tracker comes with its own charging cable, which strangely seems to be incompatible with the Charge 3 and vice versa, but Fitbit has a long history of creating new chargers for each and every model of tracker and smartwatch.

Battery life is important as no Fitbit user wants to wake up before a long walk or run to find their tracker needs charging - a feat that’s difficult to achieve while on the move, even with a power bank.

And talking of waking up, that long battery life allows Fitbit to properly monitor the quality of your sleep, which the Apple Watch can’t do if it’s charging overnight.

Fitbit app challenges leaderboard

Fitbit app and Challenges

One of the greatest things about Fitbit is the simple but mobile app, where you'll find the stat-packed customisable dashboard, Leaderboard to motivate you against/with friends and family, and special Challenges and Adventures you can set yourself or get competitive with your pals.

Alongside the usual Adventure races, there's a new Get Fit Bingo challenge, which you can invite up to 30 people to join.

Fitbit Charge 4 Bike


The recommended retail price for the Fitbit Charge 4 is £129.99 / US$149.95 / €149.95. Keep a lookout for discounts and the best Fitbit deals.

There is also a Special Edition Charge 4, selling for £149.99 / $169.95 / €169.95. This offers a couple of exclusive wristbands - including a rather natty woven one - but is no different in terms of features and functions. (In the past, Special Edition models had an extra feature or two, but this is just a unique look for that extra few pounds or dollars.)

Charge 4 vs older and cheaper Fitbits

To closest comparisons are Fitbit Charge 4 vs Charge 3, where you might find a deal on the older tracker, Fitbit Charge 4 vs Inspire 2, where you could save some money by dropping some features, and Fitbit Charge 4 vs Versa 2 where you pay more for a smartwatch with a large, colour touchscreen. 

At the entry-level, the Inspire 2 boasts a lot of what the Charge 4 offers, but lacks the built-in GPS, altimeter, and the ability to do more on the tracker itself without having to open the Fitbit app. We also prefer the Charge 4's display. Read our Fitbit Inspire 2 review

For all Fitbit models, read our full list of the best Fitbit for you - based on your needs and budget. 


We were big fans of the Charge 3, and we love the Fitbit Charge 4 a whole lot more - thanks in part to its great new features, especially the personalised Active Zone Minutes, which add a new motivational fitness metric to aim for. It’s our new favourite all-round Fitbit tracker and it bests even the Versa 2 smartwatch with its built-in GPS, and matches even the Versa 3 in many ways.

If you want on-screen workouts, a colour screen, voice assistant, and access to more apps, you’ll want to consider one of the Fitbit smartwatches. But the Fitbit Charge 4 has all the functions you need to motivate yourself to become fitter and generally healthier at a price that we think is reasonable for such a fully-featured wearable.


Fitbit Charge 4: Specs

  • Tracks steps, distance, calories burned, hourly activity, floors climbed, heart rate, swim tacking, and sleep

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