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Polar M400 review: A feature-packed GPS running watch that can also track your steps and sleep

The Polar M400 has almost everything you would want in both a running watch and daily activity tracker.

Dan Graziano Associate Editor / How To
Dan Graziano is an associate editor for CNET. His work has appeared on BGR, Fox News, Fox Business, and Yahoo News, among other publications. When he isn't tinkering with the latest gadgets and gizmos, he can be found enjoying the sights and sounds of New York City.
Dan Graziano
10 min read

Editors' note, December 23, 2014: The original review was of a pre-production unit of the Polar M400. We originally had problems with the signal strength and accuracy of the GPS. Additional testing has shown that these problems have been resolved in the retail model. As a result we have increased our rating from 3 stars to 3.5 stars.


Polar M400

The Good

The Polar M400 has good battery life, can sync wirelessly with your phone, includes GPS and activity tracking, charges through a normal Micro-USB and supports wireless heart-rate monitors. It also has automatic sleep tracking, an always-on display with a backlight, inactivity alerts and is waterproof.

The Bad

The big design may not be appropriate for all environments. There's no vibration for alerts or a silent alarm.

The Bottom Line

The feature-packed and waterproof Polar M400 offers a good set of features for beginners and advanced runners a like. It also provides feedback on your daily activities and sleep.

Editors' note, December 31, 2014: Polar's Flow app has been updated on Android with support for the M400.

Polar's latest watch looks to further bridge the gap between activity trackers and GPS running watches. The Polar M400 is the company's second GPS watch that includes tracking for things like steps taken, distance traveled, calories burned and sleep. Unlike the more expensive V800 multisport watch, however, the M400 retails for £135 in the UK, $200 in the US and AU$249 in Australia, which puts it in line with similar products on the market.

The watch, which can be had in either white or black, can also be bundled with a heart-rate monitor, although this will increase the price to £170, $250 and AU$299. If you already own a chest-based heart-rate monitor, even if it's a non-Polar monitor, it should work just fine as long as it supports Bluetooth LE (low energy), also known as Bluetooth Smart. A Garmin heart-rate sensor isn't compatible, though, Garmin uses ANT+ technology.

Polar M400: Running and activity tracking in one (pictures)

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The M400 is slimmer than other running watches, but not nearly as discrete as say the Microsoft Band . It utilizes a rubber watch strap with a security loop to sit snug on your wrist. The strap is quite soft, which makes the watch comfortable to wear, despite being so large. Don't get me wrong, though, you can still feel it on your wrist. It's not like other activity trackers, such as those from Fitbit or Jawbone, that are small and lightweight, although as far as running watches go, it's relatively comfortable.

Sarah Tew/CNET

The M400 measures 11.5mm thick and comes in at just over 56g, making it slightly heavier than the similarly priced Garmin Forerunner 15. The Garmin, however, had a cheaper and more plastic feel.

On the back of the watch you have a small rubber flap that covers a microUSB port. It's really a blessing that Polar included a Micro-USB for charging, rather than some sort of proprietary dock connector. A cord is included with the watch, which you can use with your computer or smartphone adapter as long as it outputs at least 500mA at 5V.

Sarah Tew/CNET

The port itself is actually quite interesting. You would expect the reason for the flap is to protect the port from water and while that's true, it's not the end of the world if it gets wet. The microUSB port on the M400 is actually internally waterproof (as is the watch itself) up to 30 meters, so yes you can shower and even go swimming without taking it off.

On the front of the watch there are five buttons: two on left and three on the right. The top left button activates the backlight, while the bottom left is the back and end button. The top right is for scrolling up, the middle is to select and start activities and the bottom right is for scrolling down. Some of these buttons also have secondary uses. For example, holding the top left button will enable a button lock and holding the bottom left button will sync the watch, while a long press on the top right button will scroll through the different watch faces.


The M400 has a plethora of features. While you won't see any smartphone notifications on your wrist, it can track your active time, the steps you take, distance you travel, calories you burn and your sleep at night. The GPS and other sensors gives it an extra boost, allowing it to track your distance, pace, time and altitude while running. Add in a Bluetooth heart-rate monitor and you can even track your beats-per-minute. The watch is very smart. In fact, it knows when it isn't being worn, when you are sitting, standing, walking, jogging or resting.

Sarah Tew/CNET

Speaking of running, the experience is quite enjoyable. The watch includes all the features you would expect from a running watch, with some added activity bonuses thrown in on the side. It will automatically pause when you stop running and automatically record a lap at one mile or kilometer. You can also create interval workouts based on time, heart rate or distance.

Many of the GPS running watches on the market today include a virtual pacer feature that will help keep runners on track to run a certain time. In lieu of that, the M400 includes a finish time estimator that, rather than telling you that you are running too fast or too slow, will tell how long it should take you to complete a set distance at your current pace. There is also a "back to start" feature that will help compass you back to your start point, an incredibly helpful tool for running in unfamiliar neighborhoods.

Something that annoyed me was that when I would pause a run, it wouldn't let me see any of my run stats. The only thing you are shown is the amount of time you have been running. It can be frustrating, but it isn't a deal breaker.

The M400 gives you a considerable amount of information during and after you have completed your run, all of which is displayed the devices 128x128-pixel resolution black and white display. You can view the start time, duration, distance, calories burned, fat burn percentage of calories, average pace, max pace, max altitude, ascent, descent, auto lap times, best lap time and average lap time. It will also keep track of your personal records and will notify you after you complete your longest and fastest runs. In comparison, the Forerunner 15's post-run information only displays the duration, distance, pace, calories burned, laps and any new personal records.

Sarah Tew/CNET

The M400 can store up to 30 hours of past runs on its internal storage. All of this information can also be uploaded to Polar's website and mobile app using your computer or connecting your smartphone over Bluetooth, a feature, much to my dismay, Garmin didn't include with the Forerunner 15.

As I mentioned earlier, the heart-rate monitor is chest-based. While it would have been nice for a wrist-based optical heart-rate monitor, similar to the Adidas MiCoach Smart Run , Microsoft Band and Fitbit Charge HR, chest-worn straps tend to be more accurate.

Similar to many activity trackers on the market, the M400 includes inactive alerts that will notify you when you have been idle for longer than an hour. There is also automatic sleep tracking that will kick in once you go to bed at night. I found the sleep tracking to be relatively accurate, especially since I never got any false reads from lazy Sundays on the couch.

To view your active time, calories burned and steps, you have to open the Activity menu. There is also a clever animation that shows you how much more walking, standing or jogging you must do to complete your goal, but you can't actually view your activity distance on the watch itself. You are instead required to open the mobile app or website to see this information. It's also frustrating that you must enter the Activity menu to view data about your steps and calories, rather than having the option to display them on one of the seven home screens (which aren't all that customizable)

Sarah Tew / CNET

The only customization options available on the device are four different watch faces: one with the date, time and a daily activity progress bar, another with your name replacing the progress bar, an analog face and a face with time in large numbers. I had to switch away from the progress bar face because I kept thinking my battery was low when I would quickly glance down at it.

Other features include an alarm that can be set once, daily or weekday only to wake you up in the morning, but there is no silent alarm feature or vibration like many other activity trackers.

With an active GPS signal and while using a heart-rate monitor, you can expect to get about 9 hours of battery life, which should be more than enough time for most people to finish a marathon. When used only as a watch and activity tracker that battery life jumps to around 24 days. I got about 15 days of usage with a mix of light jogging (about 20 to 30 minutes, five days a week) and daily activity tracking, although your results will vary based on how often you use the GPS.

GPS accuracy

Pressing the red center button will turn the GPS radio on. As it searches for a signal, you will be able to choose from running, cycling, swimming and an option for other indoor/outdoor activities. The time it took to acquire a signal in New York City varied. My first attempt took nearly 2 minutes, while my second and third attempts were around 45 seconds, which is in line with other GPS watches. On a rainy day it did take up to 7 minutes, though. You are also required to stand while the signal is being acquired, which can quite unenjoyable in the cold New York City winters. It could take up to 10 minutes for it to begin tracking you if you begin to run before the signal is acquired. Results will vary, however, and finding your location shouldn't take nearly as long outside of major cities.

Sarah Tew/CNET

Once the signal has been acquired you're ready to get started. There are five screens that you can scroll through while in workout mode. There is a screen that shows altitude data, another for heart rate, one for pace, distance and elapsed time and another with your lap time data. A single press on the bottom left square button will pause the recording, while a long-press for 3 seconds will end the workout and give you the option to save it.

In order to track the accuracy of the GPS, I ran with a Garmin Forerunner 15 and an older Forerunner 210. I also compared the distance results to those tracked on the website MapMyRun.com. The M400 was relatively consistent with both Garmin watches. Compared to the data I tracked on MapMyRun, the M400 accurate was off by about 0.07 miles, which isn't bad for a GPS running watch.

I ran in the streets of New York City, the trails in Central Park, the waterfront in Hoboken and the suburbs of North Jersey. I ran on cloudy days, rainy days, sunny days and days without a single cloud in the sky. While with the pre-production model, the M400's GPS failed on all of these days.

I ran the same routes with the retail model and had only two poor recordings. On a cloudy and rainy day, the GPS consistently would lose signal. Most runners care about three things: pace, distance and overall time. Pace and distance tracking are unavailable when the GPS signal is lost, leaving you with only one of the three data points you want to see, which is incredibly frustrating.

The second time that signal was spotty was when I running in New York City. It was a pretty clear day and the signal was lost for only a split second, but this can happen sometimes because of the large buildings, even with watches from Garmin, TomTom and Adidas.

Android and iOS support

The display on the M400 shows the basics: steps, calories burned and active time. More detailed information on your daily activity and runs can be viewed on the Polar Flow app for Android, iPhone, iPad and iPod touch devices and the company's website.

Holding down the left square button will sync the watch with your mobile device, while the company's FlowSync software is required to sync it from your PC to the Polar Flow website. I used the the mobile app more than the website, although the latter does include some unique features, one of which is called Relive. This feature shows you information from your runs (time, pace, distance) and will show you street view images from locations on your running route. It's somewhat gimmicky, but I enjoyed it nevertheless.

Sarah Tew/CNET

Both the mobile app and website will show you how many hours you spent resting, sitting, standing, walking and jogging. They also display the pace, distance, calories burned, automatic laps and map of your daily runs, and of course information on your steps taken, calories burned, distance traveled, active time and sleep. The app and website will also show how many inactivity alerts you received throughout the day and tell you what kind of activities you could do to reach your daily goals.

One feature I found helpful was the daily feedback I received. The Polar Flow app congratulated me if I reached my active goals for the day, but would also reminded me that sitting for extended periods of time wasn't good for my help. All in all the app and the website do a solid job of feeding your information about your activities and workouts. It also syncs with Apple's Health app on iOS 8, giving you a second option to view your data.


So let's recap, the Polar M400 is waterproof, has long battery life (not to mention it also charges with a normal microUSB), syncs wirelessly with mobile devices, can track your daily activities and supports wireless heart-rate monitors. It offers more running and activity features than the similarly priced Garmin Forerunner 15, one of which is Bluetooth so you can wirelessly sync your data with your Android or iOS device.

Now that Polar appears to have ironed out the earlier GPS problems, buyers of the M400 won't be disappointed. The watch offers a good set of features for beginners and advanced runners a like, while also providing feedback on your daily activities and sleep.


Polar M400

Score Breakdown

Style 7Features 8Ease of use 7