Garmin · 2018
Forerunner® 645Size, Dimensions & Wrist Fit
Case Width
42.5mm
Thickness
13.5mm
Diameter
42.5mm
Weight
41.8g
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.
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.
Compare the Forerunner® 645 with…
Garmin Forerunner® 645 Full Specifications
Overview1
FamilyGarmin
General9
Battery life
Smartwatch Mode: Up to 7 daysGPS mode: Up to 14 hours
Display Size1.2" (30.4 mm) diameter
Color displayYes
Lens MaterialCorning® Gorilla® Glass 3
Bezel Materialstainless steel
Memory/History200 hours of activity data
Strap materialsilicone
Display resolution240 x 240 pixels
Quick Release bandsyes (20 mm, Industry standard)
Sensors9
GPSYes
CompassYes
GLONASSYes
GalileoYes
GyroscopeYes
ThermometerYes
AccelerometerYes
Barometric altimeterYes
Garmin Elevate™ wrist heart rate monitorYes
Product Info5
Main SKU010-01863-00
Product ID591311
Product NameForerunner® 645
Release Date1/9/2018
Product VariationBlack with Stainless Hardware
Clock Features7
TimerYes
StopwatchYes
Time/dateYes
Alarm clockYes
GPS Time SyncYes
Sunrise/sunset timesYes
Automatic daylight saving timeYes
Cycling Features7
CoursesYes
Race an activityYes
Compatible with Varia™ lightsYes
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 Features7
Run workoutsYes
Race predictorYes
Foot pod capableYes
Running dynamicsYes
Performance conditionYes
GPS-based distance, time and paceYes
Cadence (provides real-time number of steps per minute)Yes
What You'll Love2
Garmin Pay™Yes
Training statusYes
Activity Profiles4
Gym
Strength, Cardio and Elliptical Training, Stair Stepping, Floor Climbing, Indoor Rowing and Yoga
SwimPool Swimming
CyclingBiking, Indoor Biking
Outdoor recreation
Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing
Swimming Features7
Pool swim workoutsYes
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 Recreation10
TracBack®Yes
Back to startYes
UltraTrac modeYes
Vertical speedYes
GPS coordinatesYes
Elevation profileYes
Total ascent/descentYes
Distance to destinationYes
Point-to-point navigationYes
Bread crumb trail in real timeYes
Daily Smart Features12
CalendarYes
ConnectivityBluetooth®, ANT+®, Wi-Fi®
Find My PhoneYes
Find My WatchYes
VIRB® RemoteYes
Weather forecastsYes
Smart NotificationsYes
Smartphone compatibilityiPhone® and Android™
Controls smartphone musicYes
Pairs with Garmin Connect™ MobileYes
Text response/reject phone call with text (Android™ only)Yes
Connect IQ™ (downloadable watch faces, data fields and apps)Yes
Activity Tracking Features11
TrueUp™Yes
Move IQ™Yes
Step counterYes
Floors climbedYes
Calories burnedYes
Distance traveledYes
Intensity minutesYes
Automatic rep countingYes
Garmin Connect™ Challenges appyes (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 Plans2
Cardio workoutsYes
Strength workoutsYes
Health & Wellness Monitoring8
Sleepyes (advanced)
Hydration
yes (in Garmin Connect™ and optional Connect IQ™ widget)
Fitness ageyes (in app)
All-day stressYes
Women's health
yes (in Garmin Connect™ and optional Connect IQ™ widget)
Resting heart rateYes
Relaxation breathing timerYes
Wrist-based heart rate (constant, every second)Yes
Kid Activity Tracking Features1
Toe-to-Toe™ Challenges app
yes (optional Connect IQ Toe-to-Toe™ Challenges app)
Training, Planning and Analysis Features34
% HRRYes
% HR maxYes
HR zonesYes
HR alertsYes
Manual lapYes
Auto max HRYes
Auto scrollYes
Finish timeYes
HR caloriesYes
Voice alertsYes
Custom alertsYes
Physio TrueUpYes
Recovery timeYes
Training loadYes
VO2 Max (Run)Yes
Course guidanceYes
Training effectYes
Virtual PartnerYes
Race an ActivityYes
Advanced workoutsYes
Interval trainingYes
Garmin Live SegmentsYes
Strava Live SegmentsYes
GPS speed and distanceYes
Configurable lap alertsYes
Customizable data pagesYes
Touch and/or button lockYes
Activity history on watchYes
Downloadable training plansYes
Training effect (anaerobic)Yes
Customizable activity profilesYes
Auto Pause® automatic timer haltYes
Auto Lap® interval tracking featureYes
HR broadcast (broadcasts HR data over ANT+® to paired devices)Yes
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Forerunner® 645 — Frequently Asked Questions
What size is the Garmin Forerunner® 645?
The Garmin Forerunner® 645 has a 42.5mm case and is 13.5mm thick.
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). Use the interactive fit tool above to check against your own wrist.
How much does the Garmin Forerunner® 645 weigh?
The Garmin Forerunner® 645 weighs 41.8g (case only; straps add weight).
What is the best way to compare the Garmin Forerunner® 645 with other watches?
Use our side-by-side comparison tool to see the Garmin Forerunner® 645 next to any other watch — case size, thickness, lug-to-lug and full specs, scaled to real proportions.