The Xiaomi Mi Band 4, as the number suggests, is the Chinese tech giant's fourth generation of its wildly popular fitness tracker.

The Mi Band has always been about offering a lot of tracking smarts for not a lot of money, and, thankfully, that doesn't change with the new Mi Band. The Mi Band 4 has now been superseded by the Mi Band 5, so check out our guide to find out how they compare.

At £35, the Xiaomi fitness band is still cheaper than Fitbit's most affordable tracker, the Inspire, and sits around the same price as the new Samsung Galaxy Fit e (not the Galaxy Fit).

For the money, you're getting activity tracking basics like step counting and sleep monitoring, but you're also getting more. For the first time, we're getting a color touchscreen display, swim tracking to make use of its waterproof design and smartwatch features, such as the ability to control music playback from your Mi Band.

Full details: Xiaomi Mi Band 5 confirmed

If you live in China, you can also take advantage of payments support, make use of the built-in microphone to enable voice commands and control smart home tech.

Even without those extras available in the Chinese version, it's still Xiaomi's most feature-packed wearable yet. However, have the new additions helped cement the Mi Band's place as the best budget fitness tracker you can get your hands on? We've been living with it for a few weeks to find out. Here's our full verdict.

Xiaomi Mi Band 4: Design and screen

Xiaomi Mi Band 4 key features 0.95-inch colour AMOLED display

Works with iOS and Android

Tracks steps/automatic sleep tracking

Heart rate monitoring

Connected GPS

Tracks swimming

Control music playback

View notifications At first glance, the Mi Band 4 look just like its predecessor, the Mi Band 3. You've still got an 18mm silicon band that holds the tracker in place. In fact, it's the same size band as the one used on the Mi Band 3. So, if you have one of those and you're planning to upgrade, keep hold of those bands.

Read this: Mi Band 4 v Mi Band 3 - the key differences

That band uses the same button clasp as its predecessor and we've had no issues of this fitness tracker falling off our wrists in our time with it. This time, you can pick up those bands in a few more colors, and the black version we had to live with is the more low-key option and emphasises that quite ordinary, sporty-looking build.

What elevates the Mi Band 4 from the 3, though, is the screen. We've now gone from a 0.78-inch sized display on the Mi Band 3 up to a significantly larger 0.95-inch colour AMOLED display with a 120 x 240 resolution. Crucially, that display is a color one now, and it makes a world of difference as far as viewing your data in all conditions and making this tracker feel a lot less budget.





Mi Band 4 (top), Fitbit Inspire (middle) and Samsung Galaxy Fit (bottom)

It's a really good, bright display, as well as offering those deep blacks you'd associate with a quality AMOLED display. Swiping through screens has a nice zip to it, and while Samsung may well be the leader when it comes to offering best in class AMOLED screens, the Mi Band 4 has a great one, too.

Below the display is still the solitary capacitive button, though it's now more clearly highlighted than it was on the Mi Band 3. Its functions are still pretty similar, but it does come in handy for some other onboard features, which we'll get into below.

There's no physical buttons here to speak of, but you will find that a heart rate monitor is still in tow. The last thing to really talk about here is the waterproofing. Xiaomi has once again slapped the Mi Band with a 5ATM rating, which means you can shower with it and take it swimming making it a tracker you can truly wear 24/7.

Xiaomi Mi Band 4: Fitness tracking

The Mi Band 4 is a fitness tracker first and foremost, and thanks to the 3-axis accelerometer and 3-axis gyroscope motion sensors, you're going to be able to count your steps, track distance and monitor calories burned.

From the tracker's watch screen, that step count can be viewed, but you can see those additional details from the Status menu screen, which is a swipe up away from the watch screen. From that Status menu you can also see the number of idle alerts you've activated. Those idle alerts indicate those periods of inactivity during the day. So, you don't want to see a lot of them, basically.

From an accuracy point of view, we've been wearing the Mi Band 4 alongside a bunch of trackers and watches, including the Polar Ignite. The sample data below gives you a sense of what we found. On the whole, the step counts were generally underreported slightly - by around 200-300 steps, on average - and this represents a big step up in performance from what we've seen on previous Mi Bands. When you jump into the Mi Fit app, you can see a nice breakdown of that activity throughout the day. It's nicely displayed on the device and in the app, and, overall, is just a really hassle-free approach to tracking your basics.

Step tracking compared: Xiaomi Mi Band 4 (left) and Polar Ignite (right)

Where there's activity tracking, there's generally also sleep tracking, and that's the case with the Mi Band 4. Thankfully, it's all done automatically, and, like step tracking, Xiaomi has stepped up its game on this front, too.

The band itself is comfortable to wear, and while you won't be able to view any sleep data on the band itself, there's plenty to dig into inside of the companion Mi Fit app. As well as recording sleep duration and offering you a sleep score, it also offers some sleep quality analysis. This can range from telling you to go to sleep earlier to acknowledging that your deep sleep was short. It will even offer sleep regularity insights, comparing average sleep data in the last week and comparing sleep data to other Mi Band users.

There's significant amount of data here, but it's presented in really digestible way and it's a massive improvement as far as what Xiaomi is trying to tell you about your bed time. There's nothing particularly groundbreaking here, but if you want to know more about your sleep, that data is there.

Sleep tracking: Mi Band 4 (left), Polar Ignite (centre) and Withings Sleep (right)

When it comes to the reliability of the sleep data the Mi Band 4 produces, it actually fared pretty well against other sleep tracking devices. We slept with the Mi Band 4 along with the Polar Ignite and the Withings Sleep bed monitor and found that, largely, the key numbers were on par.



Take the night of sleep above, which shows that the Mi Band 4 registered 20 minutes more sleep than the Polar and the Withings devices. It also managed to log the same time asleep and wake times. Data such as deep sleep was roughly the same, too, while it posted more light sleep than the Polar and the Withings. The readings and the data on the whole felt more reliable than it did on the previous Mi Band and is definitely one of the highlights of Xiaomi's new tracker.

Xiaomi Mi Band 4: Sports tracking

Along with those fitness tracking features, Xiaomi does find enough room to cram on some sports tracking skills, too. There's six workout modes in total here, letting you record treadmill running, outdoor running, cycling, walking, pool swimming and a general tracking exercise mode to cover everything else.

There's no built-in GPS here - however, somewhat surprisingly, you do get connected GPS support. That means the Mi Band 4 can use the GPS on your phone, and it's a rarity to find that kind of support on a device that costs less than £50. Even Fitbit and Samsung's cheapest trackers don't offer that functionality.

Running

Connected GPS v GPS: Mi Band 4 (left and centre) and Garmin Forerunner 945 (right)

In our running test, picking up the GPS signal from your phone is nice and zippy and then you're ready to get moving. We took it along for a 10k race (data above) and while that slither of a screen means those real-time running metrics should be cramped, the bright, vibrant display certainly made the metrics easier to absorb.

You are getting the basics here, so, time, distance and pace and there's no way to customize that data. There's also real-time heart rate data and your current heart rate zone, which you'll need to swipe up to reveal. Again, it's a solid performer, the data unsurprisingly was reliable and, ultimately, it's just nice to have that option to track with GPS and not rely on the motion sensors, which will often serve up unreliable data.



Swimming

Pool swimming tracking: Mi Band 4 (left and centre) and Polar Ignite (right)

The big new sports tracking addition is being able to activity in the pool. And it's just the pool, so no tracking in open water. When you're in the Workout screen on your Mi Band 4, you can pick the pool size, which does also offer a custom pool size option. When you're ready to move, you can view swim duration, distance and calories. The orange text on black background isn't the easiest to view in the water, but when you're taking a rest in between laps, it's perfectly fine to take in your real-time data.

When it's time to end the session, you'll need to tap the capacitive button below the screen and then swipe up and then down on the touchscreen. It sounds like it should be a nightmare to do at the end of a hard swim with wet hands, but it actually works surprisingly well.

Read this: Best fitness trackers for swimming 2019

It's only until you get out of the pool and sync your session that you can appreciate what data the Mi Band 4 can actually record. Along with the basic stats you can see during your swim you can also see average pace, calories burned, stroke type, average stroke rate and SWOLF.

The data, as far as accuracy is concerned, however, isn't great. For a 40 minute swim in a 33 metre swimming pool, it clocked us doing 3,066 metres, when the Polar Ignite and Form smart swimming goggles had us down for 1,518 metres. Now, we'd like to think we could cover that kind of distance in the pool in 40 minutes, but that is simply not the case. We know based on our usual swims that the Mi Band 4 was way off. That unfortunately means the rest of the data picked up, like average pace and average stroke rate, were wildly skewed.

It's a shame, really, because the Mi Band 4 does a half decent job here on the whole. It just doesn't look up to the job if you're big into your swimming, and hopefully this is something Xiaomi is able to address through software updates.

Xiaomi Mi Band 4: Heart rate accuracy

We didn't really have high hopes for the Mi Band 4's heart rate tracking skills, and, in fairness, our experience was a bit of a mix bag. From the device, you can take on the spot heart rate readings, and the Mi Fit app will collate heart rate recordings so you can see it at its highest and lowest. Unfortunately, resting heart rate readings were generally wildly higher than what we found on other watches with heart rate monitors. Sometimes it was identical, but most of the time it could be as much as 10 bpm higher than other watches and monitors we tested it against.





Heart rate accuracy: Mi Band 4 (left and centre) and Garmin Marq Athlete (right)



It was disappointing to see, because we initially expected it to falter in interval training, where heart rate is fluctuating quickly and tracker's often struggle to keep up. We put it through several interval treadmill running sessions and found that average heart rate and max heart rate data compared very well to a chest strap.

Take a closer look at the heart rate graphs and you can see the points during the interval sessions (when we rested) when the Mi Band 4 took longer to pick up the heart rate fluctuations. Overall, though, the Mi Band 4 did surprisingly well in th high intensity test, which makes the inconsistent resting heart rate readings all that more puzzling.

Xiaomi Mi Band 4: Smartwatch features

The Mi Band 4 is starting to accumulate some handy smartwatch features. You can now view weather forecasts, read notifications and control music playback from your phone. The benefit of having that color touchscreen makes a big difference for these features, too. The data is nicely presented and notifications are easier to read, despite the lack of screen.

The addition of the music playback controls are really useful, particularly for those times you're crammed into a train carriage and can't reach for your phone. Like other wearables that offer the functionality, once that music starts playing (it works with third-party apps like Spotify), you can swipe right from the main watch screen and skip tracks, control volume and play/pause. There's nothing revolutionary here, but it works. It's a bit tricky when you're hands are a sweaty mess, though, so keep that in mind.

Buried in the 'More' menu of the Mi Band 4 are more features like the ability to turn on a do not disturb mode, set alarms, use the stopwatch, put notifications on silent and access use the 'find your device' mode when the tracker disappears.

Like a smartwatch, you can mix it up those watch faces, too. You can do this from the band itself, but you can also do it from within the Mi Fit phone app. There's a decent array to choose from, and hopefully Xiaomi will add more in the future, too.

If you do have that Chinese version of the Mi Band 4, you will get AliPay support to enable contactless payments, though there's no indication whether similar functionality is going to make its way to other versions of the Mi Band sold outside of the company's home territory.

Xiaomi Mi Band 4: Mi Fit app

And so to the place where all of your data is synced and stored. The Mi Fit app is available for Android and iOS devices, and, while it's filled with a decent array of features and settings, it could still learn a thing or two about becoming a more intuitive place to spend time in.

The app is broken down into Workout, Friends and Profile tabs. Workout is where you'll likely spend the most of your time, because that's where you get a glance at your daily data. Our first problem here is the in-app advertisements. There's no way to turn them off and they annoyingly take up space where your data could live, instead. From that same Workout screen, you can launch tracking for walking, running and cycling, if you want to harness the GPS from your phone to map those activities.

If you are more concerned about digging deeper into your data, you need to tap on the daily activity tracking data box at the top of the dashboard to see additional data like weight, body, score, and more of those ads. It's here where you can see a breakdown of tracked workouts, and, while the app itself presents a lot of this information in a very clean and pleasant way, the steps needed to get that information feels a bit clumsy. There's a lot of similarities with Samsung's Health app, in that sense.

Xiaomi Mi Band 4: Battery life

The Mi Band comes packing a 135mAh capacity battery, which is up from the 110mAh packed inside of the Mi Band 3. Considering there's now a more potentially power-sapping to accommodate, we'd expect the battery life to drop off, but Xiaomi says you should expect the same 20-day battery life.

Based on our experience, it seems Xiaomi has managed to pull that off. Even with tracking a 2-3 intensive workouts a week, using music playback features, notifications and heart rate features, the Mi Band 4 holds up. It's lasted two weeks without charge - and that's really impressive when you consider all of the features on board.

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