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
Opinion
- It looks to have everything a running watch could ever ‘need’.
- The bits of functionality it ‘misses’ out on are not core to running.
- Personally I would prefer a sports watch appearance, but Garmin have probably made the right call with this design for the broad target market of runners
- It’s expensive BUT the onboard MUSIC could make this a ‘Kerching moment’ for Garmin’s accountants.
- The Forerunner 645 is clearly different from other Garmins in the Forerunner range.
Summary
- New format compared to style of the Forerunner 630 / 235…very similar 5 button format as Garmin 935
- Strong glass and overall ‘lightweight’
- Standard bands
- Same screen resolution as the Fenix 5/935 at 240x240px
- Battery life looks low.
- Lots of connectivity – probably every key function
- Music with c800 onboard songs and BLE headphone connectivity
- Garmin Pay (contactless effectively won’t be widely avaialble until 2018)
- It’s a cycling watch BUT it will NOT support your power meter
- It’s a pool swim watch BUT will not cache underwater HR from HRM-TRI. Not really designed for open water use with restricted functionality there.
- It’s not a triathlon watch ie it does not have multi-sport profiles
- It has no golf abilities
- It has more limited hiking-type functionalities compared to the 935./Fenix 5
- It has all the activity tracking functionality.
- Supports both BLE and ANT+ sensors
- Has almost all the clever Firstbeat physiological functionality
- ‘Obviously’ it will support Garmin’s Running Power.

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 |
General | |||
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 |
Sensors | |||
GPS | Yes | Yes | Yes |
GLONASS | 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
