The Garmin Forerunner 645 was released midway through 2018, and for a time, it was definitely Garmin’s best dedicated running watch.
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
Garmin Forerunner 245 vs Forerunner 645 - Key Differences
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
- 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
|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|
|16) XC Skiing|
|17) Stand Up Paddleboarding|
So which one should you buy?
If you're on a tight budget... Forerunner 245
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.