Garmin Forerunner 245 vs. 645: Which Should You Pick?

If you’re deciding between the Garmin Forerunner 245 vs. 645, you’re already off to a good start—both watches are some of Garmin’s better offerings, with their extra training functionalities, everyday fitness data, and smartwatch capabilities.

How do you decide which one is best for you, though? In this post, I’ll be going over the things they have in common, plus reasons to pick one over the other.

As a quick background, I’m a distance runner who trains primarily for marathons and half marathons, but I’ve done a few triathlons, and actually cross-train as often as I run. I don’t own either watch, but I had the chance to test the Forerunner 245 for a month, and was able to borrow my roommate’s Forerunner 645 for this review. I’m not a fancy fitness tech company or a career tech reviewer, but just a regular ol’ runner who wants to help you make a decision (I’ve been there before myself, and know what it’s like!).

This post contains affiliate links, meaning that I earn commission on any purchases you make. It doesn’t cost you any extra, and it would mean a lot if you purchased through my links (or just clicked through, if you’re not ready to buy yet). This income keeps my blog running, so I can write more reviews to try to help you 🙂

Things in Common: Garmin Forerunner 245 and 645

Before I get into the differences of the Forerunner 645 and 245, here’s what they have in common when it comes to fitness tracking:

• Fitness tracking for common activities: running indoors/outdoors, biking indoors/outdoors, pool swim, strength, cardio, indoor rowing, and yoga.
• Trail running capabilities: trail running specific tracking, point-to-point navigation, and UltraTrac GPS mode (turns off GPS periodically to save battery, but does make tracking a little less accurate)
• Everyday fitness stats: steps, heart rate, stress, sleep, menstrual tracking.
• “Fancier” training stats: VO2 max (aerobic performance capacity), Training Status (whether your training has been productive—this one’s funny because it will actually say “unproductive” sometimes, which I find kind of rude lol), Training Effect (how your training has improved your aerobic and anaerobic fitness), Recovery Time (how long to wait before a hard workout), and Race Predictor.

And here are the other common features of the Forerunner 245 and 645:

• Music option: you can download and play music from your watch if you’re connected to Bluetooth headphones or a speaker. You can also use Spotify Premium, Amazon Music, and Deezer. There are non-music versions of the watches, so make sure you get the music version if this feature is important to you.
• Basic smartwatch features: weather, calendar, messages, find your phone, Smart Lock (automatically unlock your phone when watch is in range).
• Safety features: LiveTrack—allows your friends and family to follow your activity in real time; Incident Detection—alerts your emergency contacts with your location if an incident is detected (you must be connected to your phone, though).
• No touchscreen: this could be a good or bad thing, but button navigation is helpful if you’re wearing gloves, or if it’s raining.

Why to Pick the Garmin Forerunner 645

Fitness-wise, the big advantage of the Garmin Forerunner 645 is its barometric altimeter. Without it, your elevation stats are less accurate, as they’ll be based on GPS. You also won’t be able to track floors climbed throughout the day. If you’re mostly a road runner, this might not be a deal-breaker, but if you’re a trail runner, hiker, or biker who wants accurate elevation stats, the Forerunner 645 is a better choice than the Forerunner 245. There is a workaround if you’re really set on the Forerunner 245 and want accurate elevation stats though: if you upload your workout to Strava, the app will correct your elevation data afterwards.

The Garmin Forerunner 645 also has more activity tracking profiles than the Forerunner 245, including: Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing (outdoor).

Appearance-wise, the Garmin Forerunner 645 looks a little more like a normal smartwatch than a fitness tracker, as it has a metal bezel. If you want to wear your GPS watch 24/7, and want it to look more discreet, the Forerunner 645 beats in the 245 here.

If you want to use Garmin Pay, you’ll also want the Forerunner 645. Garmin Pay is a contactless payment system that allows you to purchase things with your watch—you don’t even need your card or phone on you. It’s compatible with many major banks and cards, and you can use it at many retailers that accept contactless payments. Be sure to check compatibility with your country, bank, and card first though.

Why to Pick the Garmin Forerunner 245

The main draw of the Forerunner 245 is that it retails at $100 cheaper for the respective music and non-music versions. So, if the extra features of the Forerunner 645 aren’t worth another $100 for you, go for the Forerunner 245. That said, the prices on Amazon for the 645 fluctuate a lot more than that for the 245. As of late April 2020, you can actually get the Forerunner 645 Music for under $300 on Amazon, which is cheaper than both versions of the 245.

Beyond retail price point, the Forerunner 245 does have its own advantages. One of them is its longer battery life on GPS: the Forerunner 245 has 24 hours to the 14 hours of the Forerunner 645. Their battery life is otherwise comparable though; both watches last 7 days in smartwatch mode, while the Forerunner 645 lasts 5 hours on GPS with music, and the Forerunner 245 lasts 6 hours on GPS with music. If you don’t want to charge your watch as often, or if you’re planning to do longer races, you might opt for the Forerunner 245.

A new, more advanced training feature is also PacePro, which creates a pacing plan for your races and runs, based on elevation and your goal time. You can also adjust the plan based on whether you want a positive, negative, or even split, and based on whether you want to take uphills easy or hard.

On the Forerunner 245, you’ll also find Pulse Ox, which is a measurement of your blood oxygen saturation. The Forerunner 645 doesn’t have Pulse Ox. This feature basically measures how your body absorbs oxygen, which can be helpful when you sleepm or if you’re at high altitudes. Be wary though, as the Garmin pulse oximeter may not be as accurate as a device designed specifically to measure blood oxygen saturation.

Another potentially useful metric on the Forerunner 245 is Body Battery. It’s exactly what it sounds like—a measurement of your energy levels. The metric is based on heart rate variability, stress, and activity levels. It can help you better plan your workouts and days based on your energy stores, and can also help you identify trends in your overall well-being. Users have commented that it can be extremely accurate, and that lower Body Battery after a night of sleep is usually due to poor sleep, stress, drinking alcohol, eating late, or the beginning of an illness. I personally don’t find Body Battery that helpful, as I usually know how well I’m feeling, and don’t need a watch to tell me. That said, this metric can let you know exactly how much physiological damage was done that night you binge-watched Netflix or wailed karaoke until 1am 🙂

The Bottom Line

The Forerunner 245 does offer more in terms of training and fitness features, especially with PacePro, Body Battery, and Pulse Ox. That being said, the lack of barometric altimeter is really mind-boggling to me, especially as the Forerunner 245 is not a cheap watch by any means.

If you can get the non-music Forerunner 645 at its low sale price of around $220 on Amazon, that’s incredible value. At that price, I personally would go for the 645 since the additional features of the 245 (and its drawbacks) wouldn’t be worth the extra ~$60 to me (but if they’re worth that money to you, go for it!).

If you plan to get a watch with music though, then the cost of the 645 and 245 tends to be very similar on Amazon. In that case, if you don’t need a barometric altimeter or Garmin Pay, the Forerunner 245 would offer better value with its extra training and fitness features.

Basically, if you can get the Forerunner 645 at cheaper price than the Forerunner 245, and the extra training features of the 245 aren’t worth the price difference to you, then go for the 645. Otherwise, go for the 245.

Where to Buy the Forerunner 245 and 645

If this review helped you, it would mean a ton if you purchased through my affiliate links. I also want to encourage you to buy secondhand or from small, local running stores if you can. I don’t get paid if you do that, so if you still want to show your appreciation financially, you’re welcome to buy me a virtual coffee.

Garmin:

• Forerunner 645
• Forerunner 245

Amazon:

• Forerunner 645
• Forerunner 245

Other retailers:

Swappa (used electronics)
REI
Dick’s Sporting Goods

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I hope this breakdown of the Garmin Forerunner 645 vs. 245 was helpful. If you’re also considering the Vivoactive 4, check out my comparison on the Garmin Forerunner 245 vs. Vivoactive 4. Let me know if you have any questions in the comments, and happy training!