Garmin Forerunner 245 vs Forerunner 645 – Product Comparison

Garmin Forerunner 245 vs Forerunner 645 – Product Comparison

The Garmin Forerunner 645 was released midway through 2018, and for a time, it was definitely Garmin’s best dedicated running watch.

However, the Forerunner 245 was released in 2019, bringing newer technology to the table and a few bonus features that aren’t actually found in the FR645.

The aim of this guide is to make the unique features of each watch fundamentally clear. To do this, we will unpack the key differences and the key similarities, and we will also provide some simple recommendations at the end. 

Now let’s get cracking. 

Garmin Forerunner 245 vs Forerunner 645 - Key Similarities

FR245

FR645

GPS

GLONASS & GALILEO

Wrist HRM

24/7 Activity Tracking

Music Storage, Spotify & Deezer

Smartwatch Battery

Up to 7 Days

Up to 7 Days

Indoor + Outdoor Running

Indoor + Outdoor Cycling

Pool Swimming

Advanced Running Dynamics

With accessory

With accessory

Bluetooth, ANT+ & WiFi

Smart Notifications

Over 15 Sports Modes

Garmin Forerunner 245 vs Forerunner 645 - Key Differences

FR245

FR645

Price

Less Expensive

More Expensive

Pulse Oximeter

Body Battery Score

Barometric Altimeter

Payments from Watch

Stair Tracking

Running Power

With Accessory

Strava Live Segments

HRV Stress Score

Lactate Threshold

GPS Battery with Music

Up to 6 Hours

Up to 5 Hours

GPS Battery (No Music)

Up to 24 Hours

Up to 14 Hours

Total Sports Modes

16

19

Weight

38.5g

42.2g

Visual Summary of Product Features

Garmin_Foreunner_245_Black
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Garmin_Forerunner_645_Black
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Features Unique to Forerunner 645

Barometric Altimeter - Forerunner 645 Only

The benefit of a barometric altimeter is pretty clear. It gives you better incline and decline measurements than a GPS can.

Rather than relying on a satellite calculation, a barometric altimeter measures changes in atmospheric pressure to calculate vertical movements.

This is important if you do any of the following activities regularly:

  • Trail Running
  • Hill Training
  • Climbing
  • Road Cycling
  • Mountain Biking

Most road runners will be perfectly fine without a barometric altimeter, but if you take your hill training seriously, you definitely want to have a built-in altimeter.

Running Power Stats (with accessory) - Forerunner 645 Only

Even though the Forerunner 245 can give you advanced running stats (when paired with a suitable accessory), it can’t actually give you running power data.

This is because Garmin requires a barometric altimeter in order to calculate Running Power.

So, if accessing running power data is important to you, the Forerunner 645 is the better choice. Also keep in mind that you will need to pair one of the following accessories to your watch in order to unlock running power on the FR645.

Payments from Watch - Forerunner 645 Only

This is another key feature that is limited to the FR645. It doesn’t require too much explanation.

You can essentially add your credit card and debit card data to your watch, and then use your watch instead of your card to make payments. 

Keep in mind that the payment terminal will need to be NFC compatible in order for you to pay with your watch. 

Strava Live Segments - Forerunner 645 Only

This is only relevant if you are a Premium Strava User. Basically it allows you to “receive notifications when approaching segments (running or cycling), as well as comparisons to their personal best times, to friends’ times, plus the current KOM or QOM.(1)

If you already use this feature or plan to use it in future, the Forerunner 645 is the watch for you.

More Data Fields On Watch Display - FR645

Even though the Forerunner 645 can handle more data fields than the Forerunner 245, the simple reality is that 4 data fields is more than enough for most people, and the FR245 can handle 4. 

So there is a small difference between the two watches here, but it’s not that important. 4 is the magic number when it comes to data fields, and both watches satisfy this requirement. 

Features Unique To Forerunner 245

Pulse Oximeter - FR245 Only

This is probably the biggest advantage that the Forerunner 245 has over the Forerunner 645.  This technology was actually first introduced with the Garmin Fenix 5X, but it is now becoming a standard feature in Garmin watches (released from 2019 onwards). 

A Pulse oximeter measures your blood oxygen saturation level. This information can then be combined with your heart rate data, to better understand the physiological state of your body. 

In other words, Garmin are leveraging information from the Pulse Oximeter, to build a better picture of your body’s health, recovery status and sleep quality. 

Body Battery Score (Stress, Activity & Recovery) - FR245 Only

According to Firstbeat.com, the Body Resources function “brings activity, stress, and recovery together for better decision making.”

The Forerunner 245 breaks this information down into a body battery score, which can be used to determine how vigorous (or easy) your next training session should be. 

Longer Battery Life - Forerunner 245

This is best explained using some simple bullet points:

  • FR245 Battery Smartwatch Mode: Up to 7 days
  • FR245 GPS Battery mode with music: Up to 6 hours
  • FR245 GPS Battery without music: Up to 24 hours
  • FR645 Battery Smartwatch Mode: Up to 7 days
  • FR645 GPS Battery mode with music: Up to 5 hours
  • FR245 GPS Battery without music: Up to 14 hours

As you can see, the Forerunner 245 dominates the Forerunner 645 in standard GPS mode (24 hours vs 14 hours). For the other battery modes (ie GPS + Music), they are basically the same (5 hours vs 6 hours). 

Garmin FR245 vs FR645 - Summary of Sports Modes

The Forerunner 245 has 13 Sports & Activity Profiles built-in, while the Forerunner 645 has 18 Sports Profiles built-in. The list below should make the differences pretty clear:

Forerunner 245 - Sports Modes Forerunner 645 - 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) Skiiing
15) Snowboarding
16) XC Skiing
17) Stand Up Paddleboarding
18) Rowing

So which one should you buy?

If you're on a tight budget... Forerunner 245

The FR245 and the FR645 are similar enough to simply choose the cheaper of the two.  This is especially true if you’re on a tight budget. While paying for less, you also gain:

  • Body Battery Score
  • Pulse Oximeter
  • Better GPS Battery Life

If you take your running seriously... Forerunner 645

The Foreunner 645 is still the better watch for serious runners. It may lack the Pulse Oximeter and Body Battery Score, but it makes up for it with:

  • Barometric Altimeter
  • Garmin Running Power Compatibility
  • Lactate Threshold Measurement

All of these features are very useful for runners, and the can only be accessed with the Forerunner 645.

With that being said, if you have your heart set on the FR245, it’s almost as good in terms of technical features, and it might actually be the better looking of the two. 

Garmin_Foreunner_245_Black
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Garmin_Forerunner_645_Black
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More Garmin Forerunner 245 Colours

Garmin Foreruner 245 Music Aqua 3
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Garmin Foreruner 245 Music Aqua
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FR245 White 1
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Forerunner 245 Black 3
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More Garmin Forerunner 645 Colours

Forerunner 645 Slate
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Forerunner 645 Slate 2
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Garmin Forerunner 645 Music Rose Gold
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Garmin FR645 Music Rose Gold
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Garmin Forerunner 645 Cherise 2
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