Garmin Forerunner 235 Review

Garmin 235
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The Garmin 235 is the first of Garmin’s watches to introduce their own optical heart rate monitor rather than licensing Mio’s technology. After great success with the Garmin 235, they’ve now added a built in heart rate monitor the the FR635, Vivoactive HR, and Fenix3 HR. The updated technology now comes in a slimmer design and with improved accuracy to boot.

Garmin 235 Features

The Garmin 235 is for the most part just an upgraded version of the Garmin 225 (which was reviewed here). But what sets it apart are the stats on the new model, it places the Garmin 235 within striking distance of much pricier options like the Garmin 630 and Garmin Fenix 3 HR. It still lacks a barometric altimeter, but includes other “premium” features like cycling mode, relatively good battery life, activity tracking, bluetooth notifications, and a VO2 max estimator. Until recently, you had to spend upwards of the $400 to get these kinds of features, but they’re now becoming much more accessible. While the heart rate monitor is different than the older version, you’re not likely to notice any differences here – it still works the same way, though perhaps a bit more accurately. The biggest improvement, to me, is aesthetics. The 235 is much slimmer and sleek looking than its predecessor, and the display size is much improved.

GPS accuracy – On most of Garmin’s low to mid range watches, they only have a “smart recording”, in which the GPS recording interval varies depending on speed and acceleration to make a compromise between accuracy and battery life. At this, it does a fairly good job, but smart recording will never be as accurate as the more battery-sucking “every second” recording mode. With the 235 boasting a better battery, there is now support for every second recording. This is significantly more accurate on routes with lots of turns and on most trails. I’ve seen about a 5% accuracy improvement on my local trail route when using 1s recording intervals. I highly recommend using this setting for short runs where you care more about accuracy than battery life. Long story short though, the GPS accuracy on the 235 is on par with other Garmin watches; the only thing worth noting here is the ability to choose the recording interval.

Optical Heart Rate Monitor – Optical heart rate monitor mean that you don’t wear a chest strap but it is instead measured through a sensor on the back of the watch. The accuracy is surprisingly good – amazing actually – for usage during steady state efforts when your heart rate isn’t changing super quickly, but still a bit shaky when dealing heart rate spikes. For things like interval training you will want to stick to a chest strap monitor if you want instant and perfectly synced data.


In addition to Optical heart rate tracking on runs, you also have the option of 24/7 heart rate monitoring. Just like during runs, it performs very well when not dealing with HR spikes. Chances are it will be right on when you’re checking your HR at your desk at work, but when you stand up to walk to the bathroom it will take some time to lock on and probably deviate up and down significantly. At the end of the day, I’m really happy with how the 235 performs 90% of the time, but would still recommend a chest strap for testing things like maximum heart rate or workouts involving short duration intervals.

Battery Life – Interestingly, battery life seems to be a bit variable, with different users reporting different numbers. This is likely due to the number of configurations with which you can use the watch. Disabling the HR sensor and using smart recording will get you up to 16 hours of battery life, whereas you’re likely to get 6 hours or so with HR enabled and 1s recording intervals; probably about 10 hours out of the box with factory settings.

Likewise, there’s a lot of variability with standby battery life as well. You’re going to get between one and four weeks in watch mode depending on your activity level, your settings, and how often you press buttons.

Overall, battery life here is really good for a watch with a built in HRM at this price point. Disabling HR puts the watch in the same league as watches like the 920xt, Fenix3, an Ambit3, making the watch suitable for many ultramarathoners (though you’d have to be elite to make it through a 100 miler with the watch still alive).

High Resolution Display – The display is really great compared the 225, which is especially great for obstacle races when the display is likely to have a layer of mud over it, limiting readability. The bright backlight, larger watch face, and high contrast makes the watch easy to ready in low-light, direct sun, and even with a layer of dust/dirt. While it seems like a minor point, it really is nice to see your stats at a glance instead of having to bring the watch 6 inches closer to your face and stare for a second!

Smartwatch Capabilities – The watch easily syncs with an iPhone or Android smartphone app, which you can then sync with third party apps like Strava and MapMyRun should you choose to do so. While Garmin Connect is getting better and has an arguably better mobile app than Strava, I still sync all of my activities to Strava. To me, Strava is the best place to keep track of all my activities from various devices, record from my phone if my watch is dead, and chase segments PR’s and CR’s (Garmin’s “segments” feature is lacking IMO). Sometimes the watch/app connection has a mind of its own and syncs whenever it wants to, but normally by closing and reopening the app you can get to connect right away. It does seem to have a more reliable and fast connection than it did with the 225.


Garmin 235 Usage

I’ve always been a big fan of heart rate training but, like most athletes, hate the discomfort and inconvenience of chest straps. I was really excited when I began to see optical, wrist-based heart rate monitors hit the market, but was skeptical of their accuracy; I knew the technology would improve though, and I’ve been testing various brands ever since. It was less than a year ago that I reviewed the Mio Link, and if you scan through that review it’s hard to see how far the technology is come in such a short period of time. It’s still not perfect and I’ll discuss some of the current limitations, but if you’re still wearing a chest strap for all of your workouts then you need to catch up to 2016.

I started using the 235 just as I was doing my last few weeks of training for the Georgia Death Race, so in just a two months it went a few hundred miles, went up and down thousands of feet, and I wore it pretty much 24/7. Until this watch, I’ve always opted for the top-of-the-line, dating all the way back to the 910xt in 2012. I was pleasantly surprised to find that the 235, while not exactly entry-level either, still offered many of the bells and whistles of the nicer watches and was a perfectly suitable option for my training.


On one of my longer training runs of the year, I used the 235 for about 6 hours of running and finished with about 40% battery life remaining. Not bad at all considering it was gathering heart rate data, gps data, accelerometer data and many of the other data points built into the watch for 6 hours. This run had lots of heart rate spikes as we did a lot of walk-running, stopped for water breaks, etc, and the watch did a decent job at still reporting accurately (I did a manual count periodically to check). The main inaccuracy I encountered was that it would take a while to recognize my heart rate was up again when I started running from a walk, occasionally reporting a heart rate in the 90’s for a few 3-4 minutes before “finding” it in the 140s. On this run and many other long training runs I did, there were other runners with me all sporting their own Garmin, Suunto, or Polar for me to compare data with. The 235 was generally consistent with the other Garmins, though it underestimates elevation gain compared to models with a barometric altimeter. Compared to the Suunto Ambit3, the 235 always came up short on distance, by up to a mile on longer runs in the 25+ range.

Teaser: on a local trail known for horrible satellite reception, the Garmin 235 recorded 2.32 miles and the Suunto recorded 2.40 miles. I wheeled the route as per USATF certification standards for a distance of 2.50.


Garmin 235 Durability

While not as rugged as options like Fenix and Tactix lines, the 235 is fully waterproof up to 50m and will withstand pretty much anything you throw at it. However, the wrist strap will eventually break after constant abuse. Honestly, you’ll have to beat the crap out of it through dozens of OCRs, not just standard wear and tear, but you can expect to have the rubber degrade if you’re an OCR addict that runs 20+ races a year. If you fall under this category, I’d recommend upgrading to the Fenix3.


Another thing to consider when using the 235 for OCR is that if the watch isn’t on tightly enough, mud will collect between your wrist and the heart rate sensor which will affect the accuracy. Be sure to opt for a tight fit on race day (but not cut off circulation) to ensure you’re not interfering with the optical heart rate monitor.


Garmin 235 Pros and Cons


  • Optical Heart Rate Sensor
  • Multiple GPS settings
  • HR accuracy for steady state
  • Battery Life relative to price
  • Excellent Display
  • VO2 max estimate


  • HR accuracy for intervals
  • More expensive than other “200 level” watches


Similar Products

Garmin 235Garmin 225Garmin Fenix 3TomTom Cardio
Battery Life9 days as activity monitor, 11 hours with GPS4 weeks as watch, 10 hours with GPS5 weeks as watch, 20 hours with GPS8 Hours
Heart Rate MonitorOpticalOpticalYes, with additional chest strapOptical
Waterproof 5 ATM (50 Meters)5 ATM (50 Meters)100 Meters5 ATM (50 Meters)
Weight1.5 oz1.91 oz2.9 oz.2.22 oz
Phone CompatibilityAndroid, iOSAndroid, iOSAndroid, iOSAndroid, iOS
ORM ReviewYesYesYesYes
BuyAmazonAmazon Amazon


Garmin 235 Conclusion

After extensive testing with Garmin 235, I feel confident recommending this watch to anyone and everyone looking for a watch in the $300 price range. There’s honestly not much to dislike. Sure, there’s still room for improvement with the HRM accuracy, but at the end of the day, it’s accurate enough for most practical training purposes. While your most hardcore obstacle course racing enthusiasts, ultra runners, and triathletes would be better off with a top of the line watch like the Garmin Fenix 3 or Garmin Forerunner 920XT, this is the perfect mid level option for most runners and obstacle racers today. If you haven’t jumped on the optical heart rate sensor bandwagon yet, you’re missing out!


Alec Blenis

Alec Blenis is a trail runner and obstacle course racer from Atlanta, GA. He has been on the OCR scene since 2011 and has since competed in over one hundred events, including dozens of podium finishes and overall wins.

Latest posts by Alec Blenis (see all)

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