Product Comparison

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Forerunner® 245
$299.99 USD
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Forerunner® 645
$399.99 USD

You like running. And you want to take it to the next level with a GPS smartwatch that has the basic metrics and then some.

You're an athlete with some style. You want a GPS running smartwatch with a lightweight design and heavyweight features.

General

Lens Material

Corning® Gorilla® Glass 3

Corning® Gorilla® Glass 3

Bezel Material

fiber-reinforced polymer

stainless steel

Quick Release bands yes (20 mm, Industry standard) yes (20 mm, Industry standard)
Strap material

silicone

silicone

Physical size

42.3 x 42.3 x 12.2 (mm)

Fits wrists with a circumference of 127-204 mm

42.5 x 42.5 x 13.5 mm

Fits wrists with a circumference of 127-204 mm

Color display
Display Size 1.2" (30.4 mm) diameter 1.2" (30.4 mm) diameter
Display Resolution 240 x 240 pixels 240 x 240 pixels
Display Type sunlight-visible, transflective memory-in-pixel (MIP) sunlight-visible, transflective memory-in-pixel (MIP)
Weight

38.5 g

41.8 g

Battery life Smartwatch Mode: Up to 7 days
GPS mode: Up to 24 hours
Smartwatch Mode: Up to 7 days
GPS mode: Up to 14 hours
Water rating 5 ATM 5 ATM
Memory/History 200 hours of activity data 200 hours of activity data

Clock Features

Time/date
GPS Time Sync
Automatic daylight saving time
Alarm clock
Timer
Stopwatch
Sunrise/sunset times

Health Monitoring

Wrist-based Heart Rate (constant, every second)
Daily Resting Heart Rate
Abnormal Heart Rate Alerts yes (high and low)
Pulse Ox Blood Oxygen Saturation yes (spot-check and optionally in sleep)
Fitness Age yes (in app) yes (in app)
Body Battery™ Energy Monitor
All-day Stress
Relaxation breathing timer
Sleep yes (advanced) yes (advanced)
Hydration yes (in Garmin Connect™ and optional Connect IQ™ widget) yes (in Garmin Connect™ and optional Connect IQ™ widget)
Women's Health yes (in Garmin Connect™ and optional Connect IQ™ widget) yes (in Garmin Connect™ and optional Connect IQ™ widget)

Sensors

GPS
GLONASS
Galileo
Garmin Elevate™ wrist heart rate monitor
Barometric altimeter
Compass
Gyroscope
Accelerometer
Thermometer yes (tempe™ sensor required)
Pulse Ox Blood Oxygen Saturation Monitor

Daily Smart Features

Connectivity Bluetooth®, ANT+® Bluetooth®, ANT+®, Wi-Fi®
Connect IQ™ (downloadable watch faces, data fields, widgets and apps)
Smart Notifications
Text response/reject phone call with text (Android™ only)
Calendar
Weather
Controls smartphone music
Find My Phone
Find My Watch
VIRB® Remote
Smartphone compatibility iPhone® and Android™ iPhone® and Android™
Pairs with Garmin Connect™ Mobile
Garmin Pay™

Safety and Tracking Features

LiveTrack
Live Event Sharing Android™ Only
Incident Detection during select activities
Assistance

Activity Tracking Features

Step counter
Move bar (displays on device after a period of inactivity; walk for a couple of minutes to reset it)
Auto goal (learns your activity level and assigns a daily step goal)
Calories burned
Floors climbed
Distance traveled
Intensity minutes
TrueUp™
Move IQ™
Garmin Connect™ Challenges app yes (optional Connect IQ app) yes (optional Connect IQ app)

Gym & Fitness Equipment

Automatic rep counting
Cardio workouts
Available gym activity profiles Strength, Cardio and Elliptical Training, Stair Stepping, Indoor Rowing, Yoga Strength, Cardio and Elliptical Training, Stair Stepping, Floor Climbing, Indoor Rowing and Yoga
Strength workouts

Training, Planning and Analysis Features

HR zones
HR alerts
HR calories
% HR max
% HRR
Recovery time
Auto max HR
HR Broadcast (broadcasts HR data over ANT+™ to paired devices) yes (using ANT+ or BLE)
GPS speed and distance
Customizable data pages
Customizable activity profiles
Auto Pause®
Interval training
Advanced workouts
Downloadable training plans
Auto Lap®
Manual lap
Configurable lap alerts
VO2 Max (Run)
Training Status
Training Load
Training Effect
Training Effect (anaerobic)
Improved recovery time
Daily suggested workouts yes (limited)
Custom alerts
Audio prompts
Finish time
Virtual Partner
Race an Activity
Course guidance
Garmin Live Segments
Strava Live Segments
Touch and/or button lock
Auto scroll
Activity history on watch
Physio TrueUp

Running Features

Available run profiles

Running, Outdoor Track Running, Treadmill Running, Indoor Track Running, Trail Running, Virtual Running

Running, Treadmill Running, Indoor Track, Trail Running

GPS-based distance, time and pace
Running dynamics yes (with compatible accessory)
Vertical oscillation and ratio yes (with compatible accessory)
Ground contact time and balance yes (with compatible accessory)
Stride length (real time) yes (with compatible accessory)
Cadence (provides real-time number of steps per minute)
Performance condition
PacePro™ Pacing Strategies
Run workouts
Race predictor
Foot pod capable

Outdoor Recreation

Available outdoor recreation profiles

Skiing, Snowboarding, XC Skiing, Stand up Paddleboarding, Rowing

Point-to-point navigation
Bread crumb trail in real time
Back to start
TracBack®
UltraTrac mode
Elevation profile
Distance to destination
Vertical speed
Total ascent/descent
GPS coordinates

Cycling Features

Available cycling profiles

Biking, Indoor Biking

Biking, Indoor Biking

Alerts (triggers alarm when you reach goals including time, distance, heart rate or calories)
Courses
Race an activity
Compatible with Varia Vision™ (head-mounted display)
Compatible with Varia™ radar (rear-facing radar)
Compatible with Varia™ lights
Speed and cadence sensor support (w/sensor)

Swimming Features

Available swim profiles

Pool Swimming

Pool Swimming

Pool swim metrics (lengths, distance, pace, stroke count, swim efficiency (SWOLF), calories)
Stroke type detection (freestyle, backstroke, breaststroke, butterfly) (pool swim only)
Drill logging (pool swim only)
Basic rest timer (up from 0) (pool swim only)
"Repeat on" rest timer (pool swim only)
Auto rest (pool swim only)
Countdown start (pool swim only)
Pool swim workouts
Underwater wrist-based heart rate
Heart rate from external HRM (real-time during rests, interval and session stats during rests, and automatic heart rate download post-swim) yes (with HRM-Tri™, HRM-Swim™ and HRM-Pro™)

Kid Activity Tracking Features

Toe-to-Toe™ Challenges app yes (optional Connect IQ Toe-to-Toe™ Challenges app) yes (optional Connect IQ Toe-to-Toe™ Challenges app)