Garmin · 2018
Forerunner® 645Size, Dimensions & Wrist Fit
The Garmin Forerunner® 645 sits best on flat wrist widths of about 45–61mm (≈ 12.0–16.3cm wrist circumference). Adjust the slider below to check your wrist.
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The Forerunner® 645 in short
The figures that decide whether this watch suits you, pulled out of the full specification sheet further down.
- Rated for 14 hours of use per charge.
- 13.5mm thick. Thicker than 68% of 43mm watches — it will sit noticeably high on the wrist.
- 1.2" (30.4 mm) diameter display.
- Corning® Gorilla® Glass 3 case, Corning® Gorilla® Glass 3 glass.
Does the Forerunner® 645 fit your wrist?
Drag the slider to your wrist width and see the Forerunner® 645 overlaid at true scale. Lug-to-lug — not case diameter — decides whether a watch overhangs your wrist.
Happy with the fit? Check current availability for the Forerunner® 645.
Check offer2D Dimension Schematics
The Forerunner® 645 drawn to scale — from above, and in profile against the wrist.
- Garmin Forerunner® 64542.5mm · 13.5mm thick
3D preview
Garmin Forerunner® 645 on a wrist
On an arm sized to your own wrist — the view a product photo never gives you.
Shapes are built from published measurements, not manufacturer 3D models — accurate proportions, generic dial.
Forerunner® 645 battery life
The runtime the manufacturer publishes for everyday use.
- Smartwatch14 hours
How the Forerunner® 645 ranks on battery
Against the 268 Garmin watches in our database, ranked on each figure Garmin publishes.
- Everyday use7 days#208 of 257
- GPS tracking14 hours#194 of 233
Forerunner® 645 specifications
The figures that decide a purchase, followed by every line Garmin publishes.
- Battery life
- Smartwatch Mode: Up to 7 daysGPS mode: Up to 14 hours
- Display
- 1.2" (30.4 mm) diameter
- Resolution
- 240 x 240 pixels
- Bezel
- stainless steel
- Glass
- Corning® Gorilla® Glass 3
- Strap
- silicone
- Storage
- 200 hours of activity data
Full specification sheet
136 published lines across 17 groups, unedited
Overview
- Family
- Garmin
General
- Battery life
- Smartwatch Mode: Up to 7 daysGPS mode: Up to 14 hours
- Display Size
- 1.2" (30.4 mm) diameter
- Color display
- Lens Material
- Corning® Gorilla® Glass 3
- Bezel Material
- stainless steel
- Memory/History
- 200 hours of activity data
- Strap material
- silicone
- Display resolution
- 240 x 240 pixels
- Quick Release bands
- yes (20 mm, Industry standard)
Sensors
- GPS
- Compass
- GLONASS
- Galileo
- Gyroscope
- Thermometer
- Accelerometer
- Barometric altimeter
- Garmin Elevate™ wrist heart rate monitor
Product Info
- Main SKU
- 010-01863-00
- Product ID
- 591311
- Product Name
- Forerunner® 645
- Release Date
- 1/9/2018
- Product Variation
- Black with Stainless Hardware
Clock Features
- Timer
- Stopwatch
- Time/date
- Alarm clock
- GPS Time Sync
- Sunrise/sunset times
- Automatic daylight saving time
Cycling Features
- Courses
- Race an activity
- Compatible with Varia™ lights
- Speed and cadence sensor support (w/sensor)
- Compatible with Varia™ radar (rear-facing radar)
- Compatible with Varia Vision™ (head-mounted display)
- Alerts (triggers alarm when you reach goals including time, distance, heart rate or calories)
Running Features
- Run workouts
- Race predictor
- Foot pod capable
- Running dynamics
- Performance condition
- GPS-based distance, time and pace
- Cadence (provides real-time number of steps per minute)
What You'll Love
- Garmin Pay™
- Training status
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
- Drill logging (pool swim only)
- Countdown start (pool swim only)
- "Repeat on" rest timer (pool swim only)
- Basic rest timer (up from 0) (pool swim only)
- Stroke type detection (freestyle, backstroke, breaststroke, butterfly) (pool swim only)
- Pool swim metrics (lengths, distance, pace, stroke count, swim efficiency (SWOLF), calories)
Outdoor Recreation
- TracBack®
- Back to start
- UltraTrac mode
- Vertical speed
- GPS coordinates
- Elevation profile
- Total ascent/descent
- Distance to destination
- Point-to-point navigation
- Bread crumb trail in real time
Daily Smart Features
- Calendar
- Connectivity
- Bluetooth®, ANT+®, Wi-Fi®
- Find My Phone
- Find My Watch
- VIRB® Remote
- Weather forecasts
- Smart Notifications
- Smartphone compatibility
- iPhone® and Android™
- Controls smartphone music
- Pairs with Garmin Connect™ Mobile
- Text response/reject phone call with text (Android™ only)
- Connect IQ™ (downloadable watch faces, data fields and apps)
Activity Tracking Features
- TrueUp™
- Move IQ™
- Step counter
- Floors climbed
- Calories burned
- Distance traveled
- Intensity minutes
- Automatic rep counting
- Garmin Connect™ Challenges app
- yes (optional Connect IQ app)
- Move alerts (displays on device after a period of inactivity)
- Auto goal (learns your activity level and assigns a daily step goal)
Workout and Training Plans
- Cardio workouts
- Strength workouts
Health & Wellness Monitoring
- Sleep
- yes (advanced)
- Hydration
- yes (in Garmin Connect™ and optional Connect IQ™ widget)
- Fitness age
- yes (in app)
- All-day stress
- Women's health
- yes (in Garmin Connect™ and optional Connect IQ™ widget)
- Resting heart rate
- Relaxation breathing timer
- Wrist-based heart rate (constant, every second)
Kid Activity Tracking Features
- Toe-to-Toe™ Challenges app
- yes (optional Connect IQ Toe-to-Toe™ Challenges app)
Training, Planning and Analysis Features
- % HRR
- % HR max
- HR zones
- HR alerts
- Manual lap
- Auto max HR
- Auto scroll
- Finish time
- HR calories
- Voice alerts
- Custom alerts
- Physio TrueUp
- Recovery time
- Training load
- VO2 Max (Run)
- Course guidance
- Training effect
- Virtual Partner
- Race an Activity
- Advanced workouts
- Interval training
- Garmin Live Segments
- Strava Live Segments
- GPS speed and distance
- Configurable lap alerts
- Customizable data pages
- Touch and/or button lock
- Activity history on watch
- Downloadable training plans
- Training effect (anaerobic)
- Customizable activity profiles
- Auto Pause® automatic timer halt
- Auto Lap® interval tracking feature
- HR broadcast (broadcasts HR data over ANT+® to paired devices)
Alternatives to the Forerunner® 645
Watches that cover a similar amount of wrist, with the measurements that separate them.
Garmin
Forerunner® 645 Music
- Width
- 42.5mm
- Thick
- 13.5mm
- Weight
- 42.2g
Garmin
Forerunner® 570 - 42mm
- Width
- 42.4mm
- Thick
- 12.9mm
- Weight
- 42g
Garmin
Forerunner® 245
- Width
- 42.3mm
- Thick
- 12.2mm
- Weight
- 38.5g
Garmin
Forerunner® 245 Music
- Width
- 42.3mm
- Thick
- 12.2mm
- Weight
- 38.5g
Garmin
Vivoactive 6
- Width
- 42.2mm
- Thick
- 10.9mm
- Weight
- 36g
Garmin
Vivoactive 5
- Width
- 42.2mm
- Thick
- 11.1mm
- Weight
- 36g
Forerunner® 645 — Frequently Asked Questions
Will the Garmin Forerunner® 645 fit my wrist?
The Garmin Forerunner® 645 looks balanced on flat wrist widths of roughly 45–61mm (about 12.0–16.3cm circumference). Drag the slider above to check it against your own measurement.
How long does the Garmin Forerunner® 645 battery last?
Garmin rates it at 14 hours per charge in everyday use.
How does the Garmin Forerunner® 645 battery compare with other Garmin watches?
At 7 days in everyday use it ranks #208 of the 257 Garmin watches in our database — below the middle of the range. The full ranking, including GPS and power-saving figures, is on our Garmin battery life comparison.
Is the Garmin Forerunner® 645 thick for a 43mm watch?
At 13.5mm, thicker than 68% of 43mm watches — it will sit noticeably high on the wrist. Thickness, not case width, is what decides whether a watch catches on a shirt cuff.
What other watches are the same size as the Garmin Forerunner® 645?
OnePlus Watch 3 43mm, Oppo Watch X2 Mini, Omega Speedmaster Moonphase Stainless Steel / Black Meteorite / Bracelet, Zenith Defy Extreme Diver Shadow / Bracelet all sit within half a millimetre of the Garmin Forerunner® 645's 42.5mm case, so they cover the same amount of wrist.
