Polar M400 review

This sports watch with activity-tracking smarts gets the Wareable treatment

The wallet-friendly younger sibling to the Polar V800, the M400 is one of the first fitness devices to bridge the gap between the fitness band and the GPS sports watch. For £169/$179, it offers full activity tracking from your wrist, whether you're walking up the office stairs or speeding through your local park on a 5km training run.

Polar M400: Design and build

While it does have some multisport credentials (it will track the GPS related stats for cycling and even horse riding) the M400 is built to be a running watch with added intelligence.

Let's face it, being the younger relation to a multi-talented piece of tech like the V800 was always going to be difficult but the M400 stands up remarkably well.

Guide: Using Polar Flow

Unlike the V800 it won't pair up with quite as many accessories and cycling cadence sensors are not an option, but on the plus side, the design is actually better than its rather pricier stablemate.

For starters the strap is more comfortable on the wrist. Added to that the watch face is a little smaller and more ergonomic.

Then there's the simple USB charging that does away with the need for a unique charging cable or dock; a bone of contention with many other GPS watches, including the V800. Despite this, it still manages to be fully water-resistant in water up to 30m, taking the activity tracking element off of dry land.

There's also a high-contrast display that makes it easier to see your stats even in direct sunlight.

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It's a real shame that it doesn't have the built-in heart rate monitoring that some running watches like the Adidas miCoach Smart Run or the TomTom Cardio Runner now offer, but it can be paired with a chest strap for added accuracy andthe Polar staple heart rate zone training.

Weighing in at 56.6g and measuring 11.5mm thick, it's also not the bulkiest of the running watches, which adds to the overall comfort.

Polar M400: Features

Let's start with what the M400 tracks. There is, of course, the basics including distance, pacing, altitude and calorie burn. But where the M400 cuts a new path is in its ability to deliver data for the times when you're not running.

The internal accelerometer of the unit will track steps, activity and sleep. It'll also give you a nudge if you've been stationery for a long period just like you'd get from a Jawbone UP24 or a Fitbit Flex.

The Activity Guide feature is basically like having a Polar Loop built into your running watch.

Polar M400 watch review

While the activity and sleep tracking don't offer the depth of some of these devices, having all your data pushed to a single platform is extremely appealing to the point that you're happy to forgo some of the deeper data.

In terms of running, one of the features we found most useful was the Back to the Start feature that guides you home via the most direct route using a GPS marker stored at the start of each run. It's brilliant for running in a foreign city, or for people who just tend to get lost easily.

There are also a range of smart coaching features just like those we've seen on the V800 and competitors like the Garmin Forerunner 220 or 620.

Running guide: Using your running watch for interval training

Running Estimator calculates how long it'll take you to cover a distance at the pace you're currently clocking, while PB support gives you feedback on any records you've broken during a run.

There's also handy post-run feedback on the overall training benefit from the work you've just done. This helps you determine whether you've been burning fat, improving cardio and what effect this has had on your body. Running Index gives you a window into how your running is improving based on heart rate and speed. This is great if you're training towards a specific goal.

The Polar smart calorie counter is far more accurate than you would get with a regular fitness band as it takes into account your height, weight, age, gender and activity levels to form a much more accurate estimate off the calories you are using during exercise.

The Polar fitness test has been developed from years of trial and error, and is now so accurate it rivals any lab-based sub-maximal VO2 test. Using heart rate data and fluctuations at rest it will provide you with a VO2 max figure, that you can use to track your performance in just 5 minutes of testing.

If you're not entirely sure what this means, check out our GPS running watch jargon buster.

Notifications have recently been added to the M400 mix. The bad news is it's iOS only for now, but the good news is that all smartphone notifications will appear in your iPhone's Notification Center; that's WhatsApp, Facebook, Instagram, Twitter, the whole shebang.

You can choose whether notifications make a sound or just appear on screen, and there's a handy 'do not disturb' function as well.

Polar M400: Syncing, apps and web tools

Polar M400 review

Thanks to Bluetooth Smart technology, all the data from your M400 can be easily, and instantly, synced to a connected smartphone. Your vitals end up in the Polar Flow app and web tool, which both offer a competitive range of options to enhance your training. From customisable training plans to elite athlete level data, Polar Flow is one of the best tracking tools we've come across.

Running guide: How to stay injury free with wearables

It might not have the gloss and social features that Nike+ Running has, or the range of off-the-shelf training plans you get with Adidas miCoach, but it's a great tool for runners.

Polar M400: Battery life

A full charge of the M400 will get you around eight hours of GPS tracking. On that front it's competitive with most of the other running watches in this category.

When it comes to the day-to-day tracking or general watch mode you're looking at closer to 21 days. That's a lot more than most fitness bands.

Polar M400
By Polar
Bang for your buck, the Polar M400 is a fantastic option for anyone looking for a wearable that offers a complete picture of everyday activity and training. If you’re a serious cyclist there are better products out there and some runners might like to see more running form data but for anyone who’s about to take on their first marathon or just embarking on the couch-to-5km, then this is as good as any device you’ll find right now.

  • Full 360 tracking
  • USB charging
  • Decent battery life
  • No built in HR monitor
  • Activity tracking is basic
  • Lack of accessory support

What do you think?

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  • wndll·

    How would you compare this to the Garmin FR220? I currently got into running and found the FR220 to be a good tool, but I think I'm ready for the next step, and the 620 is a lot more expensive for so few features. Syncing with different services (endomondo, ranker, etc) would be cool, but not a deal breaker. Would you consider the M400 to be a step up from the FR220?

  • KieranAlger·

    Hi Wndll, good to hear that you're getting into your running. The Forerunner 220 is a solid running tool. In terms of upgrading it depends on what's most important to you right now in your training. Are you looking for more running form insights or do you want something that can help you decide when to train, for example?

    I'd say the M400 is comparable with the 220 but with added general activity tracking which is less about your running and more about you overall health.

    The next level up in both cases would be the Garmin FR 620 or the Polar V800. I'd definitely say you've got to be looking to get involved in a lot of the running dynamics and serious detail to make it worth upgrading to either.

  • Eddy9928·

    Can M400 use build-in internal accelerometer for running on treadmill or need extra footpod (costly)?

    • p.lamkin·

      It doesn‚Äôt ‚Äď you‚Äôll need a footpod.

  • nxel·

    Hi there, congrats for the good review and also battery life, That's my worry now. I'm between 2 devices: polar m400  for 170 euros (Which I've seen daily activity tracker is not using GPS, is that right?, where the battery life it's good) and the suunto ambit 2s (Which I've seen in a second hand shop for 190 euros. I don't know if suunto is worth it in all aspects, battery life and functionality, can you help me please? I'm a mountain runner (15km average-  2 days a week) Thanks!

    • j.stables·

      As a mountain runner, we would probably urge you to seriously look at the Suunto for the added stats. The M400 is more of a road running watch with daily activity tracking added on. That said, the Polar Flow ecosystem and insights are excellent. Suunto will give you more run data when you're on the slopes. Hope that helps.

  • zul·

    iam going to korea.. polar watch have a store at seoul?

  • p.lamkin·

    It uses a paired heart rate monitor 

  • Suprie·

    hi, can i paired this with other HR Monitor such as Wahoo TICKR Run? 

    • p.lamkin·

      Yes, it should connect using Bluetooth Smart. However, Polar recommends using its h7 monitor

  • Bartoon·

    Can I make the heart rate monitor function work (via the chest strap) if I do not have a GPS signal e.g. in a gym?

  • Bartoon·

    do I have to have a valid GPS signal before I get a reading from the paired HR monitor?  The HR field is blank when I'm in the gym.  Thanks.

  • Lavender_90·

    is this also good for weights and crossfit?

  • Alex_·

    Just purchased this watch. It was a bit steeper than what I expected to spend, and I had been looking at the latest activity tracker type wearables, but I couldn't be happier with my purchase!

    Here are some of the reasons (in no particular order)

    - It's a good looking device. In black, it can be worn all day long. It's subtle and unobtrusive, flush and not bulky at all. Could be any other type of sportswatch

    - It's SUPER comfortable and light. Because it used a chest strap (which I prefer, more on that later) and because it can be worn as a normal watch (NO OHR tracking) it doesn't need to be tight against my wrist. I can wear it a little looser, so it's bound to be much more comfortable and not induce any rash.

    - Pairing with the web platform (through computer) or straight to the app works brilliantly

    - Chest strap. Not convinced by by OHR monitoring. It's a fad, one that is still not properly implemented and in infancy stage, and that requires a lot of user "sacrifice" , to make it work properly (snug fit). That means I have to adapt to the device instead of the other way around

    - App quality on iPhone really strong. All I need is there. I see no need to use run keeper or apple health. Comprehensive syncing and tracking, what else do you need?

    - Price. Ok, a little more than what I thought I'd spend (200 euros) But after looking at other wearable tech options, it's actually not as bad. Fitbit surge retails for about 140 euro's I think? For only 60 euros more, you've got a real professional product, with accurate heart rate tracking. Even a casio Gshock is easily 150-170 euros. So all in all... Ok, compared to a Gshock it's not nearly as strong, but I'll live.

    - Activity tracking! Combines the latest craze in fitness bands, with a proper workout watch. (minus the constant heart rate monitoring, but don't care)

    - I read battery live is great. Can't speak to that yet, but certainly better than the continuous charging you need to do with OHR devices. Nothing I hate more than charging devices, especially bands and watches. So that's great!

    - Chest strap: don't have a problem with that. Putting on a chest strap is easy enough. Much easier and more convenient than strapping a phone to your arm imo. I definitely wanted a standalone device which this is. I always hated strapping the phone on. You need to find the pouch first, than fiddle with the phone to squeeze it in there, then put it on your arm. And if you want to check something while running, the screen is probably facing away from you. If I want music, I'll just clip on an ipod shuffle or something. 

    All in all, happy to have chosen for a standalone watch. Maybe I could have made a better choice by getting a Garmin or suunto but they were way more expensive too. All the bands are, for me anyway, not yet mature and at the moment more hype and inconvenience, and not that practical...

  • Doron·


    Great review, but not really helping me. I am a bit in limbo here and could really use some advice. I am looking for a device that will motivate me and keep track of some stats such as paces, km's, altitude steps (walking stairs), but also keeps a track of sleep and a good and reliable GPS tracker. Most importantly, I want to pair it with my iPhone to be able to keep track of all my stats and improvements. 

    I've been reading lots of reviews and blogs, but I feel that the more I read, the more I am getting more confused. 

    What would you recommend between this Polar M400, the Fitbit Surge or the Apple Watch or can you recommend a better alternative?


    • j.stables·

      Seems like the Surge is a good bet!

  • Lodan·

    This seems like a silly question, but does the M400 have a basic stopwatch feature?

  • chrisfrisco·

    My daughter has been using a Garmin Forerunner 25 but is frustrated by the fact that the backlight does not stay on.  Therefore, she's having to press the backlight button on the watch frequently.  Is there a device that is comparable to the Forerunner 25 or the Polar M400 whose backlight stays on or can be programmed to stay on during an entire evening run?

    • yongbr·

      I have a Garmin Vivoactive and it has an option from 8 sec to "stay on" under setting.

  • jetlee·

    How does the Polar m400 compare to the Suunto Ambit 3 Run? According to my research the Polar has more features but lacks in battery life.  I like the look of the clear crisp display of the Polar especially in direct sunlight. The aesthetics of the Suunto looks a bit cheap in my opinion.  Would anyone like to perhaps make their recommendation?

    • Ricky·

      You probably have already made a purchase decision, but I have the Ambit 3 Sport and the M400.  I feel the Ambit is better made, and is heavier than the M400.  There still isn't a cadence feature for indoor running on the M400, which to me is just plain dumb since all my cheaper watches have this feature.  Plus, it has no stopwatch feature.  Talk about a ripoff.  I also like the Navigation Features on the Sport.  However, I know the Run does not have those features.  I also like the watch strap on the Suunto better, really nice.  Overall the M400 is a nice watch, and you can't beat the display.  It is better than the Suunto in that aspect.  Accuracy is close to the Suunto, but not as good.

  • sachivm·

    can the Apple Watch do everything the m400 can? Would you buy te m400 or wait for Apple Watch 2?

    • scorpio516·

      No.  Apple watch doesn't have GPS.  Apple watch can't do structured workouts.  Apple watch can't use an accurate HR strap.

      Frankly, the Apple watch isn't a fitness watch and is next to useless to use as one, compared to actual fitness watches.

      • Jarek·

        actually, you're wrong!

        Apple Watch 2 has gps, while gen 1 use gps from your iphone...

        TyWatch 2 can read 3rd party hr belt as well.

        As for structured workouts itdepends on app you will use, so it is plenty of choices and you're not limited by producer as in any polarwatch!

        Btw. Polar m400 doesn't have simple stopwatch or countdown timer!

  • Jo-Platten·

    Hey everyone, I want a fitness watch but don't want to spend over $250ish. I'm interested in the Polar M400 but want to be able to sync it to strava on my Samsung....is that possible? Also, does this watch have a pedometer inbuilt? Can anyone recommend a watch which is 'sleek' enough to wear all day, under $250, reliable, able to syncto strava and has an inbuilt pedometer? Thanks in advance!!!! :)

  • Ral·

    Me and my wife both have Polar M400. My wife's one started giving problems with charging a while ago, the watch was sent to the seller for replacement. Recently...., a night before my ultra marathon Two oceans in Cape town South African, my watch started having similar charging problems like my wife's. I am done with Polar. What a good looking watch....I mean so user friendly. But this charging issues is a let down.

  • DJC·

    Wondering if the M400 can show average pace and current pace on one screen at the same time?

  • Catshell·

    I love the idea of the back-to-back start option via GPS, as I frequently get lost on runs when off road but I am looking for something that I can also listen to music from, like the Tom Tom.  Does anyone know of a fitness watch that has both features? 

  • dm1·


    Questions:  Do you know when it will work with Android system, can you set it up for interval training if so, is it straight forward, does it have an alarm to wake you up as most wearables do?

    Thank you

  • Jeuler·


    So I have read a bunch of your reviews on different devices but am at a loss. I want to buy my wife a new running watch but see they have the triathlon ones as well so when she does go cycling she can track it. If money is not a concern what is the best watch to get. She runs everyday likes to track progress, splits etc.. She will track miles including waking so I figure get somethjng that works well. Currently she has an old Garmin and uses runkeeper on her phone. Thanks in advance,


  • ReggiePlate·

    I've had my Polar M400 for over a year now and I'm very pleased with it. It does everything that I want. Customer service is always excellent and as I'm fortunate to live only a couple of miles away from their HQ, I just pop in if I have any difficulties. The staff are so friendly and helpful.

  • Rparadowsk·

    I use M400 with h7 and I have recently began using with Tickr X sensor. Work great for HR but when I use it with GPS, it records geography and displays path on Polar Flow however, it does not track/ display distance nor pace. I would have thought the gps related functions are watched based.  Therefore do I have a faulty watch unit?