The Forerunner 645 Music has the latest Garmin look with a round watch case and face and replaceable 20mm silicon band with quick release system.

The watch has a face of 42.5mm and weights 45-ish grams. The screen is sharp – even though not to the level of an Apple Watch or one of the latest Samsung Gear watches – and is very readable, especially outdoors. I keep mine at 50% brightness to help with the battery life and I can always get the info I need from the watch with a glance during the day.

Compared to the VivoActive 3 Music which I reviewed a few days ago, the major design element of the ForeRunner 645 is a beautiful steel bezel which is sloped from the glass towards the case of the watch. I really like this design feature and at a glance give to the Forerunner 645 Music an expensive, elegant look. Combined with the ability of easily changing inexpensive straps, it is a watch that I don’t mind wearing all day in many different contexts.

One the side of the watch are 5 physical buttons: light, up, down, start/stop and back. On the back there are the socket for the charger and the Elevate wrist heart rate sensor.

The full list of sensors included in this watch is:

• GPS
• GLONASS
• Garmin Elevate™ wrist heart rate monitor
• Barometric altimeter
• Compass
• Gyroscope
• Accelerometer
• Thermometer

Which is the same list of sensor as in the $150 cheaper VivoActive 3 Music.

The charger cable is an alligator-clip style that clips around the watch. It’s a very secure way of locking on to your watch and I actually leave it dangling from a plug in the wall.

The ForeRunner 645 Music does NOT have a touchscreen, leaving all the navigation to the 5 physical buttons on the side of the watch.
Before getting into the details, here’s my general opinion of physical buttons vs touchscreen.

In my opinion a performance-oriented watch needs physical buttons. They allow you to operate the watch without even looking at it, which is especially useful while running. Touchscreens start to become tough to operate when it’s raining or simply when you are sweating.

5 buttons might seem overkill, but I actually find that in this watch is a perfect number and after getting used to it, they are quite intuitive.

Here’s a quick overview of the buttons:

• The “light” button turns on the backlighting of the watch face. When long-pressed it brings up the “quick menu” which allows you quick access to things such as the wallet, key lock, stopwatch, timer…
• “Up” and “Down” buttons are used to navigate through the widgets – taking you from the basic watch face to things like weather, notifications, running and other activity stats etc. They obviously navigate up and down any menu you are in currently.

  Long pressing “Up” brings up the wach setup menu while long pressing “down” from any screen, including during a run, brings up the music menu.

• The “Start/Stop” button opens the “activity” widget, allowing you to select what activity to start tracking. The button acts as a “enter” key in all the other menus.
• The “back” button obviously navigates you back from where you are, but also doubles as a lap tracker during a run, end of set during a swimming session and so on.

Details aside, the physical buttons are one of the main differentiators between this watch and the VivoActive 3 Music, or actually between a watch that is specific to running and a smartwatch/activity tracker.

While it might be difficult at first to get used to all the buttons and their functions, they become quite natural after a while (took me a week before being able to do stuff without having to think too much about it) and right now after two months of use I can just go to wathever menu I need almost without looking at the screen.

I cannot stress enough how much better physical buttons are for serious sport activity. I can cycle through the screens without fear of inadvertently navigating out of the menu or pausing something… especially when raining, or swim training they are so much better than touchscreen.

The Forerunner 645 (music) is a mid-high range performance running watch so I had high expectations going in.

Satellite acquisition is usually near-instantaneous even though at times I had to wait up to a minute for the watch to pick up my location. I can’t pinpoint why it would make me wait longer at times, especially when starting from the same place as where my last run ended. Luckily this is the exception and not the rule, but it still happens.

Garmin 645 Music with the data fields I use while running.

The watch is lightweight, the dial is large but sits well on the wrist. I don’t think I could ask more in terms of fit and comfort. The dial has amazing readability even under full sunlight. If you are running at night you’ll have to turn the back light on, but you can set it so that it will only stay on during the run and not continuously (battery saver!).

Before I continue talking about using the Forerunner 645 Music during an actual run, let me walk you through some of the options you can choose before you run.

• Run Settings: you can customize your data screens (how many and what information on each). I personally use a custom screen with 4 data fields: timer, distance, current heart rate and cadence. I can easily press the up/down button to access other data I might want to look at, such as pace.
  You can add alerts, from obvious things such as heart rate, pace etc that will let you know when you go over specified thresholds you set, to more personal ones such as reminders to eat/drink after a certain time or distance, or to go back home after a certain distance/time…

• Training: in here you can select the workouts you downloaded from Garmin Connect or perform standard ones such as intervals, alternating run/walk. You can run a test for your lactate threshold (requires a separate chest HRM strap), race a previous run of yours..
• Navigation: this menu allows you to load up courses you previously uploaded from Garmin Connect or create new ones directly from the watch. You can also simply select “back to start” when you are lost and the watch will direct you to where you started.

So now for the run itself. As I mentioned the watch is lightweight and the screen is clearly legible at a glance. I usually run with a 4 data field screen with black fonts on white background (all customizable) and there’s enough resolution to read all 4 clearly while on the move.

I set up automatic laps of 1km and once I completed a lap, the watch face displays the time for the last lap and if you have your headphones on it will give you a quick voice message about it.

Overall I can’t fault the 645 while running at all. It performs as expected and my expectations were high to start with.

This is not specific to the 645 only, but common to all the Garmin GPS watches. Your stats and activities will live on the Garmin Connect software eco-system and it’s a system I am growing to like more and more as I use it.

Activities will sync automatically over wifi after you are finished and the “Physio TrueUp” function will synchronise your data across all your garmin devices. This function is extremely useful for people like me who test/use more than one device so that whatever I am wearing has all my history independently from what device I was wearing at the time and I believe it will be appreciated by people who use Forerunner devices for their runs and Edge devices for cycling.

Garmin Connect is a good suite of dashboards, widgets and screens that give you both an insight on your activity level (steps, floors, sleep, calories in vs calories out thanks to MyFitnessPal integration…) and the list of your sport activities with good level of detail.

Talking about runs specifically, what I like is the ability to check speed, cadence, heart rate all at the same time while locating yourself on the map. What I mean is if you click on a certain spot on the map of your run, you’ll see right below how you were doing in terms of those metrics.

You will be able to check your lap performance and the time spent in different heart rate zones too.

The Garmin 645 comes preloaded with a ton of other sport activites that you can track. The ones I used the most besides running are swimming, cardio and strength training.
I was happy and impressed with the swim accuracy – even though it only tracks pool swims, no open water – and coming from the VivoActive 3, physical buttons make using the watch for swimming much easier and reliable.

Although it’s meant to be a GPS watch for running, it makes for a very decent 24/7 activity tracker as well, measuring your heart rate continuously and keeping track (and goals) of everything from steps to floors and calories in/out.

Since you connect the watch to your phone you can enable notifications. This is really personal. At times it’s really useful, like when I am on my bike and I receive a text: I can see who sent it and what it’s about without having to reach for my phone. At time it’s annoying when you are receiving a few emails and your wrist keeps buzzing.

Luckily like almost everything else on this watch, the notifications are customizable .

Possibly because they have very similar hardware, but I found the battery life of the 645 Music to be on par with the one from the VivoActive 3 Music. This means 4 full days of battery with heart rate active every second and including 30-45 minutes of sport activity every day. Sometimes with GPS, sometimes without.

GPS I found it “honest”. It’s not perfect but it’s quite consistent. There are a couple of loops I usually do and I get my lap notification (1km) where I expect the kilometre markers to be. You’ll see in the picture below that sometimes the watch mistakes your position and places you on top of buildings – but I never found these discrepancies to be bad enough to skew the results of my training.

The obvious “other interesting function” for the Garmin 645 Music is.. the music part of it.

There are good news and bad news. Good news is that loading music and podcasts onto the watch is straightforward enough: you connect the watch to your computer via USB and synchronize between files on the computer and files on the watch. It would have been perfect if this could have happened wirelessly, but I am being picky here.

There is also the option of using streaming services: iHeartRadio and Deezer. I haven’t tried them yet but the best news is that Garmin announced Spotify connection on the Fenix 5 Plus family of watches… and everyone’s expectation is for this integration to trickle down to the other music enabled devices.

If it will work as it does on the Fenix, this means you’ll be able to sync playlists to be downloaded on the watch.

The not so good part of this for me is that the connection with the headphones can be hit or miss. Testing it with the same headphones I tested the VivoActive 3 Music, a pair of Jlabs Epic 2, the audio skipped a lot, to the point that sometimes I had to stop listening.

UPDATE: There has been a software update for the watch in the past weekend (to version 4.0) and most of the changes have been to the Music interface: apparently now the watch will sync music automatically when on wifi! Also, the update improved the Bluetooth reception for me. It’s not perfect, but it’s much better than initially was.

The Forerunner 645 Music competes with a few other Garmin watches.

To start, with the Forerunner 645 without music, which retails for $50 less. It is the same watch for every function aside from music.

Another obvious competitor is the VivoActive 3 Music. This activity tracker (it’s not part of the ForeRunner family) has basically the same hardware as the 645, and retails for $150 less. It is a though comparison. The 645 is a better watch for runners, period. The physical buttons, the advanced metrics and ability to get even more detailed data if connected to a cadence pod or Garmin heart rate strap… all these details are noticeable and useful. But it’s $150 more, and you will need to spend another $60 or so to actually access the advanced metrics.

If money is not an issue, I will recommend the 645 without doubt. But if you are budget conscious, the VivoActive 3 Music offers a lot for the price point.

Other competitors in a similar price range are the new Polar Vantage watches, which we are just now starting to review.

If the price is not an issue, buy this watch. I have been using it for more than two months and I really like it. From a design standpoint it’s really well designed: both functionally and aesthetically.

There are some quirks to be ironed out still (in primis the Bluetooth connection to the headphones) but the amount of information you get about your runs, the extreme customisation of the screens, battery life and the fact that it works as a great 24/7 activity tracker justify its price in my opinion.

Go for the VivoActive 3 Music if the price is too steep, but if you are serious about measuring your performance, the ForeRunner 645 is the GPS watch to beat in the mid-price range.

Have a look at our selection of the best GPS running watches of 2018.