Garmin Forerunner 645 vs Forerunner 945 – Product Comparison

Garmin Forerunner 645 vs Forerunner 945 – Product Comparison

This is truly a battle of the Forerunners. 

On one side we have the Garmin Forerunner 645, which is essentially Garmin’s premium dedicated running watch (although the Forerunner 245 gives it a solid run for its money. You can check out that comparison here). 

On the other side we have the Garmin Forerunner 945, which is arguably the best watch that Garmin has ever made in terms of price, value and total features (as of this writing). 

But before we get into the nitty gritty, it’s worth mentioning the most important difference between these two watches. Here it is:

Garmin Forerunner 645 vs Forerunner 945 - Key Similarities



Wrist HRM

24/7 Activity Tracking

Stress Monitoring

Sleep Tracking

Indoor + Outdoor Running

Indoor + Outdoor Cycling

Pool Swimming

Music Storage & Apps

Payments from Watch

V02 Max Estimates

Stryd & Runscribe Compatible

Garmin Running Coach

Advanced Running Dynamics

With Accessory

With Accessory

Garmin Running Power

With Accessory

With Accessory

Garmin Forerunner 645 vs Forerunner 945 - Key Differences


Less Expensive

More Expensive

Open Water Swimming

Triathlon Mode

Body Battery Score

Pulse Oximeter


Golf Mode

Improved Garmin Elevate HRM

Garmin ClimbPro

Sports Modes



Visual Summary of Features

Forerunner 645 - Features Summary

Forerunner 945 - Features Summary

Features Unique to the Forerunner 645

Apart from the silver bevel of the watch face and the less expensive price, the FR645 has no unique features when compared to the FR945. 

This doesn’t mean that the Forerunner 645 isn’t awesome. It simply confirms just how powerful the FR945 really is. The product equation below should give you a pretty good understanding of what the 945 can do.  

Garmin Forerunner 945 = Forerunner 245 + Forerunner 645 + Fenix 5 Plus

That’s not an overstatement. The FR945 can do everything the Fenix 5 Plus can do, and it has a few extra features that are only found in the FR245. You can see the full FR945 vs Fenix 5 Plus product comparison here

Long story short, in the year 2019, the FR945 is Garmin’s star player.

Features Unique to the Forerunner 945

Open Water Swimming - FR945 Only

Only the Forerunner 945 gives you the ability to track your swims using the in-built GPS. The bullet points below should clear up any confusion on this point:

  • Pool Swimming – FR645 & FR945
  • Open Water Swimming – FR945 Only

Triathlon Mode - FR945 Only

This was mentioned at the beginning of the article but it’s worth repeating. The biggest difference between these two watches is that the Forerunner 945 has a triathlon mode. 

This allows you to track each key discipline of a triathlon (swimming, biking and running) and switch between each discipline with the simple press of a button. 

If you’re a triathlete, you really don’t have to do any further research. The FR945 has everything a triathlete could possibly need, and it has more technological features than the Garmin Fenix 5 Plus. 

Body Battery Score - FR945

Garmin’s body battery score is one of the company’s key innovations in the last 12 months. 

In essence, it uses data heart rate data,  blood oxygen saturation levels, sleep quality and total exercise time to calculate your body battery level. 

The higher your body battery charge, the harder you can push yourself during your next training session. On the other hand, if your body battery score is really low, it’s probably best to take it easy during your next few sessions, or to make time for some solid sleep sessions.

Garmin’s body battery score is likely to become a staple ingredient of all their future GPS watches and activity trackers. It’s built into the FR945 but sadly it’s missing from the FR645. 

Pulse Oximeter - FR945 Only

The primary purpose of a pulse oximeter is to measure your blood oxygen saturation levels. That may sound great, but you’re probably wondering why it’s useful. 

To cut a long story short, Garmin uses the Pulse Oximeter in the FR945 to measure your blood oxygen levels, which is then used to help calculate the following:

  • Stress Tracking
  • Advanced Sleep Monitoring
  • Altitude Acclimation
  • Body Battery Score

When Garmin first introduced the Pulse Oximeter in the Fenix 5 Plus, it was mainly used for altitude acclimation. However, their ability to leverage this technology has improved since then, and they are now using it to better measure the physiological state of your body. Hat’s off to Garmin for setting industry trends with this technology.

TOPO Maps - FR945

There’s a part of me that finds it difficult to believe that Garmin included TOPO maps with the Forerunner 945.

This particular feature has always been limited to the Fenix series, but that mould has officially been broken.

TOPO maps are basically beautiful representations of your surrounding landscape, displayed on the screen of your watch. You can use the maps to navigate pretty much any outdoor terrain (provided you have the Maps downloaded), which is super useful for hikers, trail runners, mountain bikers and adventure racers.

Golf Mode - FR945 Only

This is only relevant to golfers, but it’s a big deal for people who play 18 holes regularly. The Garmin Forerunner 945 gives you access to the following golf specific features:

  • Yardage to front, middle and back of green
  • Shot distance tracking (Garmin Autoshot)
  • Digital scorecard
  • Hazards and course targets
  • Digital scorecard

As a super passionate golfer, this is a deal breaker for me. I would choose the FR945 over the FR645 based on this feature alone.

That being said, if you don’t play golf, you obviously shouldn’t let this feature affect your decision. 

FR645 vs FR945 - Sports Modes

Forerunner 645 - Sports Modes Forerunner 945 - Sports Modes
01) Strength Training 01) Strength Training
02) Cardio Training 02) Cardio Training
03) Elliptical Training 03) Elliptical Training
04) Stair Stepping 04) Stair Stepping
05) Indoor Rowing 05) Indoor Rowing
06) Yoga 06) Yoga
07) Running 07) Running
08) Treadmill Running 08) Treadmill Running
09) Indoor Track Running 09) Indoor Track Running
10) Trail Running 10) Trail Running
11) Cycling 11) Cycling
12) Indoor Cycling 12) Indoor Cycling
13) Pool Swimming 13) Pool Swimming
14) Snowboarding 14) Snowboarding
15) XC Skiing 15) XC Skiing
16) Stand Up Paddleboarding 16) Stand Up Paddleboarding
17) Outdoor Rowing 17) Outdoor Rowing
18) Floors Climbed 18) Floors Climbed
19) Golf Mode
20) Open Water Swimming
21) Triathlon Mode
22) Hiking
23) Kayaking
24) Skiing
25) Mountain Biking
26) Climbing

So which one should you buy?

There’s no question that the Forerunner 945 smokes the Forerunner 645 in terms of total features. It’s the better looking, more talented younger brother that will always make the FR645 envious. 

But that doesn’t mean you should automatically buy the Forerunner 945, mainly because you have to pay quite a bit more for all those extra features. 

In my opinion, it comes down to this: 

  • If you focus primarily on running – FR645
  • If you do triathlons – FR945
  • If you play golf – FR945
  • If you’re on a tight budget – FR645
  • If you want the best multisport GPS Watch in the world – FR945

9 thoughts on “Garmin Forerunner 645 vs Forerunner 945 – Product Comparison

  1. Straight forward, Easy to read (with out all the meaningless pretty bullshit others put in) as well as a great comparison chart …..thank you

  2. I know the review focuses most on running, but since it does mention cycling (and even golf!!) there is a significant difference worth keeping in mind. The 645 does NOT support any kind of cycling power meter. So if you would like to see your cycling power, even occasionally (e.g. in a gym), you cannot do that with the 645, whereas you can with the 945. Ask me how I know 🙁

    • I’m gonna take a stab and say you bought the Forerunner 645 ?
      In all seriousness though, I may look into adding a row for cycling power in future reviews, and update this particular review so cyclists are in the know.
      And thanks for reading the blog.

      • You are correct, I bought it. Now, the lack of cycling power is not a big deal to me (I am mostly a runner, I do not have cycling power hardware on my bike), I discovered it just out of curiosity at the gym during an indoor bike sessions (when it was too cold to run or ride out), but I think it’s pretty important to some.

        For the rest, thank you for putting together such great reviews, I was undecided about which FR to buy among all, and you helped me pick the 645 which has really been great for me

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