Garmin Forerunner® 645 vs Garmin Forerunner® 645 MusicSize, Specs & Wrist Fit Compared
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Garmin
Forerunner® 645 (010-01863-00)
Garmin
Forerunner® 645 Music (010-01863-30)
The Garmin Forerunner® 645 and Garmin Forerunner® 645 Music share a near-identical 42.5mm case, so wrist presence comes down to thickness, lug-to-lug and weight.
Specification Comparison
| Spec | GarminForerunner® 645 | GarminForerunner® 645 Music |
|---|---|---|
| Case Width | 42.5mm | 42.5mm |
| Thickness | 13.5mm | 13.5mm |
| Weight | 41.8g | 42.2g |
| Shape | Circular | Circular |
| GPS | Yes | Yes |
| Battery life | Smartwatch Mode: Up to 7 daysGPS mode: Up to 14 hours | Smartwatch Mode: Up to 7 daysGPS mode without music: Up to 14 hoursGPS mode with music: Up to 5 hours |
| Released | 2018 | 2018 |
Full Specification Comparison
252 specs| Spec | Garmin Forerunner® 645 | Garmin Forerunner® 645 Music |
|---|---|---|
| Overview | ||
| Family | Garmin | Garmin |
| General | ||
| Battery life | Smartwatch Mode: Up to 7 daysGPS mode: Up to 14 hours | Smartwatch Mode: Up to 7 daysGPS mode without music: Up to 14 hoursGPS mode with music: Up to 5 hours |
| Display Size | 1.2" (30.4 mm) diameter | 1.2" (30.4 mm) diameter |
| Color display | Yes | — |
| Lens Material | Corning® Gorilla® Glass 3 | — |
| Bezel Material | stainless steel | — |
| Memory/History | 200 hours of activity data | — |
| Strap material | silicone | Silicone |
| Display resolution | 240 x 240 pixels | — |
| Quick Release bands | yes (20 mm, Industry standard) | — |
| Lens material | — | Corning® Gorilla® Glass 3 |
| Bezel material | — | Stainless steel |
| Colour display | — | Yes |
| Memory/history | — | 200 hours of activity data |
| Display Resolution | — | 240 x 240 pixels |
| Quick release bands | — | Yes (20 mm, Industry standard) |
| Sensors | ||
| GPS | Yes | Yes |
| Compass | Yes | Yes |
| GLONASS | Yes | Yes |
| Galileo | Yes | Yes |
| Gyroscope | Yes | Yes |
| Thermometer | Yes | Yes |
| Accelerometer | Yes | Yes |
| Barometric altimeter | Yes | Yes |
| Garmin Elevate™ wrist heart rate monitor | Yes | Yes |
| Product Info | ||
| Main SKU | 010-01863-00 | 010-01863-30 |
| Product ID | 591311 | 612476 |
| Product Name | Forerunner® 645 | Forerunner® 645 Music |
| Release Date | 1/9/2018 | 1/9/2018 |
| Product Variation | Black with Stainless Hardware | With Black Coloured Band |
| Clock Features | ||
| Timer | Yes | — |
| Stopwatch | Yes | — |
| Time/date | Yes | — |
| Alarm clock | Yes | — |
| GPS Time Sync | Yes | — |
| Sunrise/sunset times | Yes | — |
| Automatic daylight saving time | Yes | — |
| Cycling Features | ||
| Courses | Yes | — |
| Race an activity | Yes | — |
| Compatible with Varia™ lights | Yes | — |
| Speed and cadence sensor support (w/sensor) | Yes | — |
| Compatible with Varia™ radar (rear-facing radar) | Yes | — |
| Compatible with Varia Vision™ (head-mounted display) | Yes | — |
| Alerts (triggers alarm when you reach goals including time, distance, heart rate or calories) | Yes | — |
| Running Features | ||
| Run workouts | Yes | — |
| Race predictor | Yes | — |
| Foot pod capable | Yes | — |
| Running dynamics | Yes | — |
| Performance condition | Yes | — |
| GPS-based distance, time and pace | Yes | — |
| Cadence (provides real-time number of steps per minute) | Yes | — |
| What You'll Love | ||
| Garmin Pay™ | Yes | Yes |
| Training status | Yes | — |
| Training Status | — | Yes |
| Activity Profiles | ||
| Gym | Strength, Cardio and Elliptical Training, Stair Stepping, Floor Climbing, Indoor Rowing and Yoga | — |
| Swim | Pool Swimming | — |
| Cycling | Biking, Indoor Biking | — |
| Outdoor recreation | Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing | — |
| Swimming Features | ||
| Pool swim workouts | Yes | — |
| Drill logging (pool swim only) | Yes | — |
| Countdown start (pool swim only) | Yes | — |
| "Repeat on" rest timer (pool swim only) | Yes | — |
| Basic rest timer (up from 0) (pool swim only) | Yes | — |
| Stroke type detection (freestyle, backstroke, breaststroke, butterfly) (pool swim only) | Yes | — |
| Pool swim metrics (lengths, distance, pace, stroke count, swim efficiency (SWOLF), calories) | Yes | — |
| Outdoor Recreation | ||
| TracBack® | Yes | — |
| Back to start | Yes | — |
| UltraTrac mode | Yes | — |
| Vertical speed | Yes | — |
| GPS coordinates | Yes | — |
| Elevation profile | Yes | — |
| Total ascent/descent | Yes | — |
| Distance to destination | Yes | — |
| Point-to-point navigation | Yes | — |
| Bread crumb trail in real time | Yes | — |
| Daily Smart Features | ||
| Calendar | Yes | — |
| Connectivity | Bluetooth®, ANT+®, Wi-Fi® | — |
| Find My Phone | Yes | — |
| Find My Watch | Yes | — |
| VIRB® Remote | Yes | — |
| Weather forecasts | Yes | — |
| Smart Notifications | Yes | — |
| Smartphone compatibility | iPhone® and Android™ | — |
| Controls smartphone music | Yes | — |
| Pairs with Garmin Connect™ Mobile | Yes | — |
| Text response/reject phone call with text (Android™ only) | Yes | — |
| Connect IQ™ (downloadable watch faces, data fields and apps) | Yes | — |
| Activity Tracking Features | ||
| TrueUp™ | Yes | — |
| Move IQ™ | Yes | — |
| Step counter | Yes | — |
| Floors climbed | Yes | — |
| Calories burned | Yes | — |
| Distance traveled | Yes | — |
| Intensity minutes | Yes | — |
| Automatic rep counting | Yes | — |
| Garmin Connect™ Challenges app | yes (optional Connect IQ app) | — |
| Move alerts (displays on device after a period of inactivity) | Yes | — |
| Auto goal (learns your activity level and assigns a daily step goal) | Yes | — |
| Workout and Training Plans | ||
| Cardio workouts | Yes | Yes |
| Strength workouts | Yes | Yes |
| Health & Wellness Monitoring | ||
| Sleep | yes (advanced) | Yes (Advanced) |
| Hydration | yes (in Garmin Connect™ and optional Connect IQ™ widget) | Yes (in Garmin Connect™ and optional Connect IQ™ widget) |
| Fitness age | yes (in app) | — |
| All-day stress | Yes | — |
| Women's health | yes (in Garmin Connect™ and optional Connect IQ™ widget) | — |
| Resting heart rate | Yes | Yes |
| Relaxation breathing timer | Yes | — |
| Wrist-based heart rate (constant, every second) | Yes | Yes |
| Fitness Age | — | Yes (in app) |
| All-day Stress | — | Yes |
| Women's Health | — | Yes (in Garmin Connect™ and optional Connect IQ™ widget) |
| Relaxation Breathing Timer | — | Yes |
| Kid Activity Tracking Features | ||
| Toe-to-Toe™ Challenges app | yes (optional Connect IQ Toe-to-Toe™ Challenges app) | — |
| Training, Planning and Analysis Features | ||
| % HRR | Yes | — |
| % HR max | Yes | — |
| HR zones | Yes | — |
| HR alerts | Yes | — |
| Manual lap | Yes | — |
| Auto max HR | Yes | — |
| Auto scroll | Yes | — |
| Finish time | Yes | — |
| HR calories | Yes | — |
| Voice alerts | Yes | — |
| Custom alerts | Yes | — |
| Physio TrueUp | Yes | — |
| Recovery time | Yes | — |
| Training load | Yes | — |
| VO2 Max (Run) | Yes | — |
| Course guidance | Yes | — |
| Training effect | Yes | — |
| Virtual Partner | Yes | — |
| Race an Activity | Yes | — |
| Advanced workouts | Yes | — |
| Interval training | Yes | — |
| Garmin Live Segments | Yes | — |
| Strava Live Segments | Yes | — |
| GPS speed and distance | Yes | — |
| Configurable lap alerts | Yes | — |
| Customizable data pages | Yes | — |
| Touch and/or button lock | Yes | — |
| Activity history on watch | Yes | — |
| Downloadable training plans | Yes | — |
| Training effect (anaerobic) | Yes | — |
| Customizable activity profiles | Yes | — |
| Auto Pause® automatic timer halt | Yes | — |
| Auto Lap® interval tracking feature | Yes | — |
| HR broadcast (broadcasts HR data over ANT+® to paired devices) | Yes | — |
| Clock features | ||
| Timer | — | Yes |
| Stopwatch | — | Yes |
| Time/date | — | Yes |
| Alarm clock | — | Yes |
| GPS time sync | — | Yes |
| Sunrise/sunset times | — | Yes |
| Automatic daylight saving time | — | Yes |
| Cycling features | ||
| Courses | — | Yes |
| Race an activity | — | Yes |
| Compatible with Varia™ lights | — | Yes |
| Speed and cadence sensor support (w/sensor) | — | Yes |
| Compatible with Varia™ radar (rear-facing radar) | — | Yes |
| Compatible with Varia Vision™ (head-mounted display) | — | Yes |
| Alerts (triggers alarm when you reach goals including time, distance, heart rate or calories) | — | Yes |
| Running features | ||
| Run workouts | — | Yes |
| Race predictor | — | Yes |
| Foot pod capable | — | Yes |
| Running dynamics | — | Yes (with compatible accessory) |
| Performance condition | — | Yes |
| Stride length (real time) | — | Yes (with compatible accessory) |
| Vertical oscillation and ratio | — | Yes (with compatible accessory) |
| Ground contact time and balance | — | Yes (with compatible accessory) |
| GPS-based distance, time and pace | — | Yes |
| Cadence (provides real-time number of steps per minute) | — | Yes |
| Activity profiles | ||
| Gym | — | Strength Training, Cardio Training, Elliptical Training, Stair Stepping, Floor Climbing, Indoor Rowing and Yoga |
| Swim | — | Pool Swimming |
| Cycling | — | Biking, Indoor Biking |
| Outdoor recreation | — | Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing |
| Swimming features | ||
| Countdown start | — | Yes |
| Pool swim workouts | — | Yes |
| Drill logging (pool swim only) | — | Yes |
| "Repeat on" rest timer (pool swim only) | — | Yes |
| Basic rest timer (up from 0) (pool swim only) | — | Yes |
| Stroke type detection (freestyle, backstroke, breaststroke, butterfly) (pool swim only) | — | Yes |
| Pool swim metrics (lengths, distance, pace, stroke count, swim efficiency (SWOLF), calories) | — | Yes |
| Outdoor recreation | ||
| TracBack® | — | Yes |
| Back to start | — | Yes |
| UltraTrac mode | — | Yes |
| Vertical speed | — | Yes |
| GPS coordinates | — | Yes |
| Elevation profile | — | Yes |
| Total ascent/descent | — | Yes |
| Distance to destination | — | Yes |
| Point-to-point navigation | — | Yes |
| Breadcrumb trail in real time | — | Yes |
| Daily smart features | ||
| Calendar | — | Yes |
| Connectivity | — | Bluetooth®, ANT+®, Wi-Fi® |
| Find my phone | — | Yes |
| Find my watch | — | Yes |
| Weather forecasts | — | Yes |
| Smart Notifications | — | Yes |
| VIRB® camera remote | — | Yes |
| Smartphone compatibility | — | iPhone® and Android™ |
| Controls smartphone music | — | Yes |
| Plays and controls watch music | — | Yes |
| Compatible with Garmin Connect™ Mobile | — | Yes |
| Text response/reject phone call with text (Android™ only) | — | Yes |
| Connect IQ™ (downloadable watch faces, data fields, widgets and apps) | — | Yes |
| Activity tracking features | ||
| TrueUp™ | — | Yes |
| Move IQ™ | — | Yes |
| Step counter | — | Yes |
| Floors climbed | — | Yes |
| Calories Burned | — | Yes |
| Intensity minutes | — | Yes |
| Distance travelled | — | Yes |
| Automatic rep counting | — | Yes |
| Garmin Connect™ Challenges app | — | Yes (optional Connect IQ app) |
| Auto goal (learns your activity level and assigns a daily step goal) | — | Yes |
| Move alerts (displays on device after a period of inactivity; walk for a couple of minutes to reset it) | — | Yes |
| Safety and tracking features | ||
| Incident Detection during select activities | — | Yes |
| Kid activity tracking features | ||
| Toe-to-Toe™ Challenges app | — | Yes (optional Connect IQ Toe-to-Toe™ Challenges app) |
| Training, planning and analysis features | ||
| % HRR | — | Yes |
| % HR Max | — | Yes |
| HR Zones | — | Yes |
| HR Alerts | — | Yes |
| Auto Lap® | — | Yes |
| Manual lap | — | Yes |
| Auto Max HR | — | Yes |
| Auto scroll | — | Yes |
| Finish time | — | Yes |
| HR Calories | — | Yes |
| Voice alerts | — | Yes |
| Physio TrueUp | — | Yes |
| Recovery Time | — | Yes |
| Training Load | — | Yes |
| VO2 Max (Run) | — | Yes |
| Course guidance | — | Yes |
| Training Effect | — | Yes |
| Virtual partner | — | Yes |
| Race an activity | — | Yes |
| Advanced workouts | — | Yes |
| Interval training | — | Yes |
| Customisable alerts | — | Yes |
| Garmin Live Segments | — | Yes |
| Strava Live Segments | — | Yes |
| Customisable screen(s) | — | Yes |
| GPS speed and distance | — | Yes |
| Configurable lap alerts | — | Yes |
| Touch and/or button lock | — | Yes |
| Activity history on watch | — | Yes |
| Downloadable training plans | — | Yes |
| Training Effect (Anaerobic) | — | Yes |
| Customisable activity profiles | — | Yes |
| Auto Pause® automatic timer halt | — | Yes |
| HR Broadcast (broadcasts HR data over ANT+® to paired devices) | — | Yes |
Wrist Fit
Garmin Forerunner® 645
Sits best on wrists ~45–61mm wide (≈ 12.0–16.3cm circumference).
Garmin Forerunner® 645 Music
Sits best on wrists ~45–61mm wide (≈ 12.0–16.3cm circumference).
2D Dimension Schematics
Accurate scale drawings based on case dimensions. Drag to pan, Ctrl+scroll to zoom. Works for every watch regardless of photo availability.
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Frequently Asked Questions
Is the Garmin Forerunner® 645 bigger than the Garmin Forerunner® 645 Music?
Both have a 42.5mm case. Compare their thickness and lug-to-lug above to judge wrist presence.
Which fits a smaller wrist better, the Garmin Forerunner® 645 or the Garmin Forerunner® 645 Music?
The Garmin Forerunner® 645 suits wrists around 45–61mm wide, and the Garmin Forerunner® 645 Music around 45–61mm. The one with the smaller lower bound is the safer pick for a small wrist.
Can I see the Garmin Forerunner® 645 and Garmin Forerunner® 645 Music side by side at true scale?
Yes — the schematics and photos above show both watches at matched scale, and our fit tool overlays each on your wrist width.
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