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  • Garmin Forerunner 645 GPS
  • Garmin Forerunner 645 GPS Side
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GarminForerunner 645 GPS

Item # GRM0097

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  • Sandstone, One Size ($399.99)
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Item # GRM0097

Put your best foot forward.

Keeping tabs on run-savvy metrics and loaded with Garmin Pay for cashless convenience, the Garmin Forerunner 645 GPS helps you get the most out of every run, regardless if you're training for an upcoming marathon or simply getting back in shape after a long, cold winter. You'll enjoy a host of useful running features, such as wrist-based heart rate monitoring, plus advanced running dynamics when you pair it with Garmin's Running Dynamics Pod (sold separately). Additionally, Garmin's Training Status tools monitor your running history to let you know if you're on track with your training goals, as well as monitoring your training load to prevent overexertion.

Seeing you'd rather leave your wallet at home while running, the Forerunner 645 GPS features Garmin Pay for wireless payment convenience simply by waving the watch in front of a compatible payment machine at your local diner, gas station, or store. Besides wireless payment compatibility, it's loaded with ANT+, Bluetooth Smart, and Wi-Fi capabilities, so you can wirelessly sync it with a host of compatible devices, including iPhone and Android smartphones. And speaking of wireless syncing, it works seamlessly with Garmin's Connect app, so you can view all your exercise stats on a smartphone or computer for an in-depth analysis of your running stats and exercise output.

  • Smartwatch helps you gain the most out of every run
  • Garmin Pay wireless technology for cashless convenience
  • Wrist-based heart rate for tracking physical output
  • Advanced Running Dynamics provide insightful run data
  • Garmin's Training Status tools monitor running history
  • Embedded GPS receiver for measuring distance and speed
  • ANT+, Bluetooth Smart, and Wi-Fi for wireless syncing
  • Syncs with Garmin Connect app for iPhone and Android
Tech SpecsWeight
Tech Specs
Cancer & Reproductive Harm -
Housing Material
[bezel] stainless steel
Strap Material
Face Material
chemically strengthened glass
yes, step counter
yes, GPS-based distance, time, and pace
yes, barometric altimeter
Heart Rate Monitor
yes, wrist-based heart rate monitor
Technical Features
Garmin Pay wireless payments, wrist-based heart rate, Advanced Running Dynamics
yes, Bluetooth, ANT+, Wi-Fi
Operating System
Garmin Connect IQ, Garmin Connect Mobile app (iOS, Android)
Date Indicator
yes, time/date
yes, alarm clock
5 ATM water-resistant rating
Battery Type
rechargeable via USB cable
Battery Life
[Smartwatch] up to 7 days, [GPS mode] up to 14 hours
Forerunner 645, charging cable
Face Size
42.5 mm
Recommended Use
running, training
Manufacturer Warranty
1 year

Claimed Weight

Claimed weights are provided by the vendor.

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1.5 oz
41.8 g

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I have issues

  • Familiarity: I've put it through the wringer

I have had this watch about 100 days and all of a sudden it will not charge. I have cleaned the charging connectors per Garmin's advice and it still will not charge. I have to do a hard restart about every ten to 14 days because the watch will just lock up. I love the features of this watch - but I am extremely frustrated with the charging issue and intend to return the watch, and look for something else.

Good, but some metrics are wonky

  • Familiarity: I've used it several times

This is a great GPS watch. It tracks HR as well as distance and elevation, which are key for runs or hikes. The only downside is that the tracking seems a little off. If I'm recording with a friend or on another device, it always seems to be less with the GPS watch. Kinda weird! The HR monitor isn't the best either, but that's what I'd expect for a wrist HR monitor vs a chest strap.

Wonderful quality GPS HR watch

  • Familiarity: I've used it several times
  • Fit: True to size

Quality built - easy to use and quick setup pairing to my IPhone - no issues - recommended - plenty of useful widgets available

Just works

  • Familiarity: I've used it several times

I've had this about a month and so far, everything is working great. GPS and heart rate monitoring appear accurate and the interface if fairly intuitive, especially if you're used to other Garmin devices. Battery usually lasts 5 - 6 days, with GPS used for ~5 hours during that time. It has all the features I need and is far less bulky than the Fenix watches.

A Great Running Partner!

  • Familiarity: I've used it several times

Love how light and sleek it is. Gives me everything I need to know about my run and then some. I can’t take it off, would recommend to anyone interested in running!