▷ Garmin Forerunner 645 Specs | Detailed Comparison To 735XT and 935

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The Garmin Forerunner 645 is listed on Garmin’s website with the detailed specs BELOW.

The specifications are broadly ‘as expected’ several weeks ago.

A formal Garmin announcement is not now likely until around the time of CES2018.

This looks to me like the basic physical hardware of the Vivoactive 3 (with more buttons and no touch screen 😉 ) but also most tasty features of the Fenix 5/Forerunner 935 thrown in; perhaps warranting an upgrade from your Forerunner 630?

I’ll summarise the important differences and then you can read throught the detailed specs and comparisons, further below


Garmin 645 Bible Garmin 645 Review Forerunner Music


Best REI/Wiggle/PMC price is linked to. Prices approx $400-$450 or £480-£520 and UNlikely for non-Music to fall below $400 in 2019.


Garmin Forerunner 645 Music Garmin Forerunner 735XT Garmin Forerunner 935
Top-end running Watch Tri-Lite Watch Super Tri Watch
Headline RRP USA $450 $350 $500
Lens Material Corning® Gorilla® Glass 3 chemically strengthened glass chemically strengthened glass
Bezel Material stainless steel fiber-reinforced polymer
Case material fiber-reinforced polymer
QuickFit watch band compatible yes (22 mm)
Quick Release Bands yes (20 mm, Industry standard)
Strap material silicone silicone silicone
Physical size 42.5 x 42.5 x 13.5 mm 44.5 x 44.5 x 11.9 mm 47 x 47 x 13.9 mm
Weight 42.2 g 40.2 g 49 g
Water rating 5 ATM 5 ATM 5 ATM
Display type sunlight-visible, transflective memory-in-pixel (MIP) sunlight-visible, transflective memory-in-pixel (MIP) sunlight-visible, transflective memory-in-pixel (MIP)
Display size 1.2″ (30.4 mm) diameter 1.23″ (31.1 mm) diameter 1.2″ (30.4 mm) diameter
Display resolution 240 x 240 pixels 215 x 180 pixels 240 x 240 pixels
Color display  Yes   Yes   Yes
Battery life Smartwatch Mode: Up to 7 days Smartwatch Mode: Up to 11 days Smartwatch Mode: Up to 2 weeks
GPS mode with music: Up to 5 hours GPS mode: Up to 14 hours GPS/HR mode: Up to 24 hours
UltraTrac mode: Up to 24 hours without wrist heart rate UltraTrac mode: Up to 60 hours without wrist heart rate
Memory/History 200 hours of activity data 80 hours of activity data 64 MB
Clock Features
Time/date Yes Yes Yes
GPS Time Sync Yes Yes Yes
Automatic daylight saving time Yes Yes Yes
Alarm clock Yes Yes Yes
Timer Yes No Yes
Stopwatch Yes Yes Yes
Sunrise/sunset times Yes Yes Yes
Face It watch face creator Yes Yes Yes
GPS Yes Yes Yes
Garmin Elevate wrist heart rate monitor Yes Yes Yes
Barometric altimeter Yes No Yes
Compass Yes Yes Yes
Gyroscope Yes No Yes
Accelerometer Yes Yes Yes
Thermometer Yes No Yes
Daily Smart Features
Connectivity Bluetooth®, ANT+®, Wi-Fi® Yes Bluetooth® Smart, ANT+®, Wi-Fi®
Connect IQ (downloadable watch faces, data fields, widgets and apps) Yes Yes Yes
Smart notifications Yes Yes Yes
Text response/reject phone call with text (Android only) Yes No No
Calendar Yes Yes Yes
Weather Yes Yes Yes
Music controls Yes Yes Yes
Plays Onboard Music Yes No No
Music Storage up to 800 songs No No
Find My Phone Yes Yes Yes
Find My Watch Yes Yes Yes
VIRB® remote Yes Yes Yes
Smartphone compatibility iPhone® and Android Yes iPhone®, Android, Windows®
Compatible with Garmin Connect Mobile Yes Yes Yes
Garmin Pay Yes No No
Activity Tracking Features
Step counter Yes Yes Yes
Move bar (displays on device after a period of inactivity; walk for a couple of minutes to reset it) Yes Yes Yes
Auto goal (learns your activity level and assigns a daily step goal) Yes Yes Yes
Sleep monitoring (monitors total sleep and periods of movement or restful sleep) Yes Yes Yes
Calories burned Yes Yes Yes
Floors climbed Yes Yes Yes
Distance traveled Yes Yes Yes
Intensity minutes Yes Yes Yes
TrueUp Yes Yes Yes
Move IQ Yes No Yes
Fitness Age yes (in app) No yes (in app)
Fitness Equipment/Gym
Preloaded gym activity profiles Strength Training, Cardio Training, Elliptical Training, Stair Stepping, Floor Climbing, Indoor Rowing and Yoga Indoor Rowing, Strength Training and Cardio Training
Cardio workouts Yes Yes
Strength workouts Yes Yes
Automatic rep counting Yes Yes
Training, Planning and Analysis Features
GPS speed and distance Yes Yes Yes
Customizable data pages Yes Yes Yes
Customizable activity profiles Yes Yes Yes
Auto Pause® Yes Yes Yes
Advanced workouts Yes Yes Yes
Downloadable training plans Yes Yes Yes
Auto Lap® Yes Yes Yes
Manual lap Yes Yes Yes
Virtual Partner Yes Yes Yes
Configurable lap alerts Yes Yes Yes
V02 max Yes Yes Yes
Training Status (lets you see if you’re training effectively by tracking your training history and fitness level trend.) Yes No Yes
Training Load (your total training load for the last 7 days calculated from estimated EPOC) Yes No Yes
Training Effect (aerobic) Yes Yes Yes
Training Effect (anaerobic) Yes No Yes
Customizable alerts Yes Yes Yes
Audio prompts Yes Yes Yes
Finish time Yes Yes Yes
Race an Activity Yes Yes Yes
Auto multisport activities Yes Yes Yes
Manual multisport activities Yes Yes Yes
Course guidance Yes Yes Yes
Segments (Live, Garmin) Yes Yes Yes
Strava features (Beacon, live segments) Yes Yes Yes
LiveTrack Yes Yes Yes
Group LiveTrack Yes No Yes
Touch and/or button lock Yes Yes Yes
Hot keys No No Yes
Auto scroll Yes Yes Yes
Activity history on watch Yes Yes Yes
Heart Rate Features
HR zones Yes Yes Yes
HR alerts Yes Yes Yes
HR calories Yes Yes Yes
% HR max Yes Yes Yes
% HRR Yes Yes Yes
Recovery time Yes Yes Yes
Auto max HR Yes Yes Yes
HRV stress test (measures your heart rate variability while standing still, for 3 minutes, to provide you with an estimated stress level; the scale of this is 1 to 100; low scores indicate lower stress levels) yes (with compatible accessory) yes (with compatible accessory) yes (with compatible accessory)
Records heart rate while swimming No yes (with HRM-Tri or HRM-Swim) yes (with HRM-Tri and HRM-Swim)
HR Broadcast (broadcasts HR data over ANT+ to paired devices) Yes Yes Yes
Running Features
Preloaded run profiles Running, Treadmill Running, Indoor Track yes Running, Indoor Running, Trail Running
GPS-based distance, time and pace Yes Yes Yes
Running dynamics (with accessory) Yes Yes Yes
Vertical oscillation and ratio with accessory) Yes Yes Yes
Ground contact time and balance (with accessory) Yes Yes Yes
Stride length with accessory) Yes Yes Yes
Cadence Yes Yes Yes
Performance condition Yes Yes Yes
Lactate threshold (with accessory) Yes Yes Yes
Run workouts Yes Yes Yes
Race predictor Yes Yes Yes
Foot pod capable Yes Yes Yes
Outdoor Recreation Features
Preloaded outdoor recreation profiles Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing Hiking, Climbing, Skiing, Snowboarding, XC Skiing, Stand Up Paddleboarding, Rowing, Jumpmaster, Tactical
Point-to-point navigation Yes Yes Yes
Bread crumb trail in real time Yes Yes Yes
Back to start Yes Yes Yes
TracBack® Yes No Yes
UltraTrac mode Yes No Yes
Elevation profile Yes No Yes
Distance to destination Yes Yes Yes
Barometric trend indicator No No Yes
Storm alert No No Yes
Trail run auto climb No No Yes
Vertical speed Yes No Yes
Total ascent/descent Yes No Yes
Compatible with BaseCamp Yes No Yes
GPS coordinates Yes Yes Yes
Projected waypoint No No Yes
Sight ‘N Go No No Yes
Area calculation No No yes (via Connect IQ)
Hunt/fish calendar No No yes (via Connect IQ)
Sun and moon information No No yes (via Connect IQ)
Dual grid coordinates No No Yes
Cycling Features
Preloaded cycling profiles Biking, Indoor Biking yes Biking, Indoor Biking, Mountain Biking
Courses Yes Yes Yes
Bike lap and lap maximum power (with power sensor) No Power Yes Yes
Race an activity Yes Yes Yes
Time/distance alerts (triggers alarm when you reach goal) Yes Yes Yes
Interval training Yes Yes Yes
FTP (with accessory) No Yes Yes
Compatible with Vector (power meter) No Cycling Power Yes Yes
Power meter compatible (displays power data from compatible third-party ANT+-enabled power meters) No Cycling Power Yes Yes
Compatible with Varia Vision (head-mounted display) Yes Yes Yes
Compatible with Varia radar (rear-facing radar) Yes Yes Yes
Compatible with Varia lights Yes Yes Yes
Speed and cadence sensor support (with sensor) yes (ANT+® and Bluetooth® Smart) ANT+ Only yes (ANT+® and Bluetooth® Smart sensors)
Swimming Features
Preloaded swim profiles Pool Swimming Pool Swimming, Open Water Swimming Pool Swimming, Open Water Swimming
Pool swim metrics (lengths, distance, pace, stroke count/rate, calories) Yes Yes Yes
Stroke type detection (freestyle, backstroke, breaststroke, butterfly) Yes Yes Yes
Swim efficiency (SWOLF) Yes Yes Yes
Drill logging Yes Yes Yes
Pool swim workouts Yes Yes Yes
Open-water swim metrics (distance, pace, stroke count/rate, stroke distance, calories) No Yes Yes
Heart rate (real-time during rests, interval and session stats during rests, and automatic heart rate download post-swim) No yes (with HRM-Tri and HRM-Swim) yes (with HRM-Tri and HRM-Swim)


Fly In The Ointment


The 645 is super exciting. However my worry is that it looks a bit too much like the Vivoactive 3. And maybe it is a bit too much like the Vivoactive 3. If so this could be a Houston moment…I hope not.

Read this to see what I mean:

Garmin Vivoactive 3 Review – Detailed | Apple Watch Competitor


If you are keen for the most tech awesome running watch right now then it would have to be the Garmin 935 (reviewed here) but, be warned, that the 645 has music and Garmin Pay


Best REI/Wiggle/PMC price is linked to. Prices approx $400-$450 or £480-£520 and UNlikely for non-Music to fall below $400 in 2019.

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