Garmin Forerunner 645 Music Fitness Tracker Review


The Short Version

The Garmin Forerunner 645 Music is not the first GPS watch with music to hit the market, but it’s comfortably the best, with superb sports tracking features boosted by the addition of space for music and an eye-catching design that’s the match of any smartwatch. It’s not a stretch to say that the Forerunner 645 Music’s rounded feature set makes it the best running watch, well, ever.

Rating ⭐⭐⭐⭐⭐ (5/5)

£399.99 (£349.99 without music), buy on

Things We Liked

  • The new music feature is well integrated and easy to use. Transferring music, podcasts and audiobooks takes minutes.
  • Garmin has included all of the advanced running features found in the more expensive Forerunner 935 and Fenix 5 watches, including lactate threshold measurements, a virtual race pacer mode and running dynamics (a compatible sensor is required).
  • The design is Garmin’s best yet, with a stylish silver bezel and a smaller profile than the 935 or Fenix watches. This is a watch you can wear everywhere.
  • You can create and follow simple interval workouts on the Forerunner 645 Music, and more complicated sessions can be set up in the Garmin Connect app very quickly and synced to the watch, which then guides you through.
  • It performs everyday activity tracking well, with targets that automatically adjust based on your past activity, and the information is clearly displayed on the 645 Music and in the Garmin Connect app.
  • Battery life is a good 14 hours of GPS, or five hours if you are playing music while using the GPS.

Things We Didn’t Like

  • The 645 Music is lacking some of the features of the 935, including the open-water and triathlon modes and support for cycling power meters. The message is pretty clear – Garmin wants triathletes to buy the 735XT, 935 or Fenix watches.
  • On occasion the 645 Music’s connection with my Bluetooth headphones would drop out. Usually only for a second or so, but there was one annoying five-minute spell during a race where it kept dropping.
  • There’s no support for streaming services in the UK just yet, and there are plans only to introduce Deezer, not Spotify.
  • Garmin Pay remains limited to just one bank in the UK at the time of writing – Danske Bank. Fitness brands like Garmin and Fitbit are having trouble catching up with the likes of Apple when it comes to contactless payments through the watch.

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Garmin Forerunner 645 Music In-Depth

Using The Garmin Forerunner 645 Music For Running

The Forerunner 645 Music tracks just about everything, but it throws the kitchen sink into its running offering. There is a lot to say, but if you’re about to skip ahead know this: the 645 Music has every tracking feature a runner could want, and gives them a soundtrack.

You can have as many data screens as you want and cram them with up to four stats per screen. Going into all of the options for customisation would take more time than you, dear reader, and I can spare, but as well as the standard stats like time, distance, pace and heart rate, you can have screens dedicated to mapping your route or showing a course to follow, a virtual pacer (the only screen I use in races), guided workout information, and in-depth running dynamics. This last one requires a compatible sensor like Garmin’s HRM-TRI or foot pod, and will show advanced info like your contact time with the ground while running. It’s not for casual or even pretty darn serious runners, but its inclusion shows that the 645 Music can cater to even the most stat-obsessed.

You can also have a screen dedicated to your music and access it at any time on the watch by holding the down button. There’s be more detail about adding and organising music on the device in the smartwatch section below, but if you’re using it while running, the main concerns are how it affects the battery and how good the connection is to Bluetooth headphones. The battery takes a sizeable hit – music plus GPS means it last five hours, compared with 14 when just using GPS. That’s still enough for most races, though a marathon might be tight, but I found that the Forerunner 645 Music is at least true to that “five hours” claim, so you know you’ll be losing 20% for every hour of GPS and music and can turn off your tunes if you need GPS for longer.

The Forerunner 645 Music’s connectivity was mostly impressive. I used it as my sole source of entertainment in several runs and a half marathon, and although it dropped out from time to time it never completely let me down. At the start of the half it struggled to maintain a connection to my headphones for five minutes, which might have be down to the vast number of people turning on headphones all around me at that moment, but just when I thought I was going to be without music for an entire race it kicked in and the connection held from then on. I also must highlight how easy it is to transfer podcasts to the 645 Music, because they make up the bulk of my running entertainment and are bizarrely hard to get onto an Apple Watch where you have to use third-party apps.

The 645 Music lets you follow a set route on the watch itself while you run, directing you with a breadcrumb trail and a little arrow. You can turn on these routes during the run itself, as well as activating a back-to-start feature which comes in very handy when running in a new area. To create full routes you have to use the Garmin Connect website, but you can create quick ones based on a direction and distance with the Garmin Connect app and sync them to the watch.

Workouts can be created through the app or website and synced to the watch. Impressively, the creation takes no time at all – I once did it on the walk to the track when I realised I didn’t have my workout lined up. You can also create interval workouts on the 645 Music itself and follow it on a dedicated screen, counting down each section and keeping you on track if you have set a pace or heart rate target for certain parts of the session.

Once your session is over the Forerunner 645 Music will flag up any highlights, such as a new fastest 5K time or an improved VO2 max. There’s also an ongoing analysis of the relationship of your changing fitness (based on your VO2 max) to your training load, telling you whether the work you’re putting in is productive, unproductive, enough to maintain your fitness (maintaining), in perfect race condition (peaking), helping you to recover (recovery), overdoing it (overreaching) or letting yourself go (detraining). It also advises you how much time you should spend recovering after a session, and gives your predicted best times for 5K, 10K, half marathon and marathon distances.

In short, the Forerunner 645 Music is the ultimate training partner for runners, combining both the advanced tracking features of top GPS watches and the music usually found on smartwatches. In the past you’d have to choose between the two – the Fitbit Ionic and Apple Watch Series 3 are both great for music and other smartwatch features, but aren’t nearly as good for running tracking as the Forerunner 935, which in turn doesn’t have music. The 645 Music offers the best of both worlds.

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Using The Garmin Forerunner 645 Music For Cycling

You can customise your data screens for cycling just as you would for running, and the Forerunner 645 Music connects to separate heart rate, speed and cadence sensors via both ANT+ and Bluetooth. Wrist-worn heart rate monitors can be problematic because of the braced position of your forearm when cycling, but I found the heart rate tracking during cycling was better than I expected – during both my commutes and one intervals session indoors the 645 Music was accurate, although I didn’t try it on any long outdoor rides. It’s easy to pair a chest strap if you want to eliminate any doubt from the readings.

There is no power meter support, which will be a disappointment for cyclists but is in line with Garmin positioning the 645 Music as a running watch, rather than one for triathletes. However, one feature cyclists will enjoy is the ability to track Strava segments on the 645 Music, so if you’re competing for a specific KOM (King of the Mountain) on the app the watch will show your progress live.

Using The Garmin Forerunner 645 Music For Swimming

Before you get wet it’s worth trying to find a pool that’s at least 17m long, because that’s the minimum you can set a length for on the 645 Music. Not a huge deal for most keen swimmers, but in city gyms it’s not surprising to come across 15m pools – the two I use most often are 13m and 16m.

Once you start swimming the heart rate tracking is disabled on the 645 Music, which is out of step with other manufacturers. Suunto, Polar, Samsung and Apple devices make an effort to track heart rate from the wrist while swimming, not always successfully, but mostly well enough to make it a worthwhile feature.

As with all sports modes on the 645 Music you can set up your data screens for swimming and follow workouts in the water. Afterwards you get graphs and more detail on key swimming stats like SWOLF. Aside from heart rate, indoor swimmers get all they need from the 645 Music, but there is no open-water mode.

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Using The Garmin Forerunner 645 Music To Track Activity

The Forerunner 645 Music might be a running watch, but it’s clearly not a watch that’s only meant to be worn while running. It tracks your heart rate 24/7 and shows a graph of the past four hours (colour coded by the heart rate zone you were in), along with all the standard activity stats like steps, calories burned, floors climbed and weekly active minutes (broken down by moderate and vigorous activity). It will also track your stress with a measurement based on heart rate variability.

You can adjust the targets for steps, active minutes and floors climbed, and set steps to adjust automatically based on your past activity. Try this when you’re marathon training, for example, and your target will quickly rocket to 18,000 steps.

The Forerunner 645 Music is a sports tracker first and foremost, but its everyday tracking is the equal of anything else you’ll find on the market.

Using The Garmin Forerunner 645 Music As A Smartwatch

Music is added to the 645 Music via Garmin Express, which you will need to download on your computer. It’s easy to pick the music or podcasts you want added, and Garmin Express will also grab your iTunes playlists so you can sync them directly to the watch. There is 3.5GB of space available – around 500 songs, according to Garmin. The 645 Music is also scheduled to link to streaming service Deezer in late April or early May, if there are no delays. There is no live streaming on the watch because it isn’t cellular-enabled like the Apple Watch 3, but if you link it to a Deezer account it will update your playlists when you’re connected to WiFi so you can play them offline – a good way to make sure you don’t end up with the same music for every single run. Spotify would be more useful for most people in the UK, but it isn’t in the works.

Other standard smartwatch features on the 645 Music include notifications, and there are some apps and alternative watch faces available on the Connect IQ store, including Uber, though these mostly focus on sports.

The other key smartwatch feature is Garmin Pay, but at the time of writing this remains limited to customers of Danske Bank in the UK. Congrats if you use them. Other banks should follow, but the timeline is unclear and it seems to be a very slow process.

Using The Garmin Forerunner 645 Music As A Heart Rate Monitor

The Forerunner 645 Music tracks your heart rate throughout the day to provide both its stress and resting heart rate measurements. Having tried several Garmin devices with stress tracking I have to say I’ve never looked at it after the first couple of days, but the resting heart rate stat is useful because it’s a good overall measure of your cardiovascular fitness – if your resting heart rate is going down, your fitness is probably going up. It’s also useful, if sometimes alarming, to see your daily resting heart rate charted over the past week on the watch. Alarming because the day after a big night out, I always notice a sizeable spike in my resting heart rate the following day. Alcohol, eh?

When tracking an activity you can keep tabs on your heart rate and/or heart rate zones on a customisable data screen, and there is also a dedicated screen with a colour-coded gauge that gives your heart rate and shows you which zone you’re in. You can also train by heart rate zone when setting up a workout on the Garmin Connect app – useful if you don’t like using pace to judge intensity while running, or can’t because you’re in a hilly place where you’ll be working hard even if you’re running slowly.

I never had any issues with the accuracy of 645 Music’s heart rate tracking in any activity I tried. When running I found it reliable enough that I felt no need to wear a chest strap. Even during interval sessions there was little lag between stepping up the effort and the reading on the watch rising accordingly.

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Using The Garmin Forerunner 645 Music For Sleep Tracking

In my opinion, Garmin has never really cracked sleep tracking. All the Garmin trackers I’ve tried have trouble distinguishing between me sitting in bed reading or watching TV, and actually being asleep, which means my “total hours asleep” tally is always artificially high. This remains the case with the 645 Music. You do get a graph of your movement throughout the night, so you can actually see when you did fall asleep and wake up, even if the 645 Music believes you fell asleep earlier, and you are also given the total time spent in light or deep sleep. It’s an OK sleep tracker, but nothing more than that.

On the plus side the 645 Music is very light and comfortable to wear while sleeping, and I found that my wrist didn’t get hot or sweaty when wearing it overnight.

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The Garmin Connect App

This is probably my favourite fitness tracker partner app, and if everyone was on it rather than on Strava I probably wouldn’t bother with the latter. Garmin Connect shows all your daily stats and activities clearly on the homepage through a series of colourful cards, and you can click through them to get to more detailed info on a particular run, or your step count over the past few days, weeks or months. You also get a seven-day round-up of all the most important stats on the homepage, including averages for calories and steps, as well as total distance run and cycled. Plus, the app syncs easily with the likes of Strava so your activities are beamed over automatically.

I did, however, find that I had more trouble syncing the 645 Music with Garmin Connect than with other Garmin trackers, especially when transferring over long runs. With the Vivoactive 3, Forerunner 935 and Forerunner 35 I found that my activities would often be synced before I’d even managed to take my shoes off after getting home, but with the 645 Music I often had to open the app and refresh it a few times. It’s not a big issue, just surprising.

How Often Am I Going To Have To Charge It?

Garmin gives the battery life as 14 hours of GPS, or five hours of GPS plus music, or five days as a smartwatch. Putting music aside, I found this worked out to two charges a week, based on running four or five times plus commuting to work by bike. But who would want to put the music aside? It’s the point of the thing. Listening to podcasts or music from the 645 Music during all my running put me at three charges a week minimum.

Where Can I Wear It Without People Laughing At Me?

The Forerunner 645 Music is a terrific-looking watch, especially considering it has five buttons. Buttons make it far easier to use than a touchscreen during activities, but usually mark a device out as too sporty to wear everywhere. The 645 Music defies that convention – it is as stylish as any smartwatch.

Should I Consider Buying Something Else?

The Garmin Forerunner 645 Music is comfortably the best running watch with music available at the moment, so if that’s what you’re looking for, stop looking. Other options like the Apple Watch, Fitbit Ionic and TomTom Spark 3 (with music) all fall short of the 645 Music’s sports tracking features, which are bettered only by top-end trackers like the Forerunner 935, none of which come with music at the moment.

If you’re a runner and don’t care about music, then the obvious option is the Forerunner 645, which is £50 cheaper, but it would also be worth checking out cheaper Forerunners like the 235 or 35, or other brands’ running trackers like the Polar M430. These might not offer as great a range of features as the 645, and they aren’t as stylish, but they are still great running watches.

Moving past runners, the Forerunner 645 Music is a great daily activity tracker, but you don’t need to spend £400 just for that – Fitbit, Garmin, Misfit and many others all make terrific daily trackers for upwards of £100.

Finally, if you’re a triathlete you need to take the many hints Garmin has thrown your way and invest in a different watch – the 935 or the 735XT – or wait for a musical multisport watch to arrive.