Garmin · 2019
Forerunner 45 Size, Dimensions & Wrist Fit
The Forerunner 45 looks in proportion on wrists of 15 cm (5.9 in) and up round, and fills the wrist at 16–17.5 cm (lug-to-lug estimated at ≈48.5mm; Garmin does not publish it).
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Does the Forerunner 45 fit your wrist?
The 39.5mm suits wrists of about 14–20 cm round; the 42mm, 15 cm and up. Both work from 15 to 20 cm, where it is a choice between more skin either side (the 39.5mm) and a case that fills the wrist (the 42mm). Under 15 cm only the 39.5mm's lugs stay on the wrist; over 20 cm the 39.5mm starts to look small.
| Wrist round (mm left each side) | 39.5mm≈45.5mm lug to lug, est. | 42mm≈48.5mm lug to lug, est. |
|---|---|---|
| 14 cm / 5.5 in | Overhangs (0.2mm over) | Overhangs (1.7mm over) |
| 15 cm / 5.9 in | Sweet spot (1.4mm) | Overhangs (0.1mm over) |
| 16 cm / 6.3 in | Sweet spot (3.1mm) | Sweet spot (1.6mm) |
| 17 cm / 6.7 in | Balanced (4.7mm) | Sweet spot (3.2mm) |
| 18 cm / 7.1 in | Balanced (6.3mm) | Balanced (4.8mm) |
| 19 cm / 7.5 in | Balanced (7.9mm) | Balanced (6.4mm) |
| 20 cm / 7.9 in | Balanced (9.5mm) | Balanced (8mm) |
The Forerunner 45 in short
- The 39.5mm version is 2.5mm narrower.
- At 11.4mm, the joint 4th thinnest of the 40 Garmin watches 41–43mm across.
- 32g on the wrist. Lighter than 84% of the 37 smartwatches 42mm across that we have weights for.
Compare with another watch
Size, fit and battery side by side, against any smartwatch we list.
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Forerunner 45 battery life
Runtime by power mode
- Smartwatch7 days
- GPS13 hours
Where it ranks among Garmin watches
- Everyday use7 days#245 of 281
- GPS tracking13 hours#233 of 267
2D Dimension Schematics
- Garmin Forerunner 45 42mm × ≈48.5mm (est.) · 11.4mm thick
3D preview
Garmin Forerunner 45 on a wrist
Alternatives to the Forerunner 45
42mm · 14.1mm thick · 63g42mmGarmin
Fenix 7S Pro Solar Edition
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Epix Pro Gen 2 Standard Edition 42mm
42mm · 12.6mm thick · 44g42mmGarmin
Approach S70 42mm
42mm · 12.6mm thick · 37.2g42mmGarmin
Bounce
42mm · 14.1mm thick · 63g42mmGarmin
Fenix 7S Standard Edition
42mm · 11.6mm thick · 37g42mmGarmin
Forerunner 55
Forerunner 45 specifications
- Battery life
- Smartwatch Mode: Up to 7 days GPS mode: Up to 13 hours
- Display
- 1.04" (26.3 mm) diameter
- Resolution
- 208 x 208 pixels
- Water rating
- 5 ATM
- Glass
- chemically strengthened glass
- Strap
- silicone
- Storage
- 80 hours of activity data
- Charging
- Garmin proprietary plug charger
Show all specificationsGarmin's published specification, for reference · checked September 2026
Overview
- Family
- Garmin
General
- Battery life
- Smartwatch Mode: Up to 7 days GPS mode: Up to 13 hours
- Display Size
- 1.04" (26.3 mm) diameter
- Color display
- Yes
- Lens Material
- chemically strengthened glass
- Memory/History
- 80 hours of activity data
- Strap material
- silicone
- Charging method
- Garmin proprietary plug charger
- Display resolution
- 208 x 208 pixels
Sensors
- GPS
- Yes
- GLONASS
- Yes
- Galileo
- Yes
- Accelerometer
- Yes
- Garmin Elevate™ wrist heart rate monitor
- Yes
Product Info
- Main SKU
- 010-02156-05
- Product ID
- 641121
- Product Name
- Forerunner® 45
- Release Date
- 4/30/2019
- Product Variation
- Black
Clock Features
- Timer
- Yes
- Stopwatch
- Yes
- Time/date
- Yes
- Alarm clock
- Yes
- GPS Time Sync
- Yes
- Automatic daylight saving time
- Yes
Cycling Features
- Speed and cadence sensor support (w/sensor)
- Yes
- Alerts (triggers alarm when you reach goals including time, distance, heart rate or calories)
- Yes
Running Features
- Run workouts
- Yes
- Foot pod capable
- Yes
- GPS-based distance, time and pace
- Yes
- Cadence (provides real-time number of steps per minute)
- Yes
What You'll Love
- Display type
- Sunlight-visible, transflective memory-in-pixel (MIP)
- Water rating
- 5 ATM
- Battery life (smartwatch mode)
- Up to 7 days
Activity Profiles
- Gym
- Cardio, Elliptical Training, Stair Stepping
- Cycling
- Biking, Indoor Biking
- Wellness
- Yoga
- Indoor running
- Treadmill Running, Indoor Track Running
- Outdoor running
- Running
Daily Smart Features
- Calendar
- Yes
- Connectivity
- Yes
- Find My Phone
- Yes
- Find My Watch
- Yes
- Weather forecasts
- Yes
- Smart Notifications
- Yes
- Smartphone compatibility
- iPhone®, Android™
- Controls smartphone music
- Yes
- Pairs with Garmin Connect™ Mobile
- Yes
- Connect IQ™ (downloadable watch faces, data fields and apps)
- yes (watch faces only)
Activity Tracking Features
- TrueUp™
- Yes
- Move IQ™
- Yes
- Step counter
- Yes
- Calories burned
- Yes
- Distance traveled
- Yes
- Intensity minutes
- Yes
- Move alerts (displays on device after a period of inactivity)
- Yes
- Auto goal (learns your activity level and assigns a daily step goal)
- Yes
Health & Wellness Monitoring
- Sleep
- yes (advanced)
- Fitness age
- yes (in app)
- All-day stress
- Yes
- Resting heart rate
- Yes
- Abnormal heart rate alerts
- yes (high and low)
- Relaxation breathing timer
- Yes
- Body Battery™ energy monitor
- Yes
- Wrist-based heart rate (constant, every second)
- Yes
Safety and Tracking Features
- Assistance
- yes (smartphone required)
- Live Event Sharing
- Android™ Only
- Incident Detection during select activities
- yes (smartphone required)
Training, Planning and Analysis Features
- HR zones
- Yes
- HR alerts
- Yes
- Manual lap
- Yes
- HR calories
- Yes
- Voice alerts
- Yes
- Physio TrueUp
- Yes
- VO2 Max (Run)
- Yes
- Advanced workouts
- Yes
- Interval training
- Yes
- GPS speed and distance
- Yes
- Customizable data pages
- Yes
- Touch and/or button lock
- Yes
- Activity history on watch
- Yes
- Downloadable training plans
- 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
