Garmin Forerunner 165 vs Garmin Forerunner 645 Music

Every spec side by side, from each maker's published figures.

Only show differences

Better figure, where one is clearly better

Share comparison

Forerunner 165 compared with Forerunner 645 Music

	GarminForerunner 165	GarminForerunner 645 Music
Overview
Released
Released	February 2024	2018
Display
Case sizes
Case sizes	43 mm	42.5 mm
Panel
Panel	OLED	Memory-in-pixel
Always-on display
Always-on display	Yes	Yes
Display detail
Display detail	1.2-inch (30.4 mm diameter) colour AMOLED touchscreen, 390 x 390 pixels; optional always-on display; five physical buttons	1.2-inch (30.4 mm) sunlight-readable transflective colour MIP display, 240 x 240 pixels, with five-button control.
Screen protection
Screen protection	Chemically strengthened glass	Chemically strengthened glass.
Health and fitness
ECG
ECG	No	No
Blood oxygen
Blood oxygen	Yes	No
Skin temperature
Skin temperature	No	No
Sleep apnoea alerts
Sleep apnoea alerts	No	No
High blood pressure alerts
High blood pressure alerts	No	No
Body composition
Body composition	No	No
Fall detection
Fall detection	No	No
Crash detection
Crash detection	No	No
GPS
GPS	Single-band	Single-band
Water resistance
Water resistance	50 m	50 m
Sensors
Sensors	Garmin Elevate wrist heart rate; Pulse Ox; barometric altimeter; compass; accelerometer; thermometer; ambient light sensor; GPS, GLONASS and Galileo	GPS, GLONASS, Garmin Elevate wrist heart rate, barometric altimeter, compass, gyroscope, accelerometer and thermometer.
Health features
Health features	Continuous heart rate with high/low alerts; HRV status; Body Battery; stress, respiration and blood oxygen; advanced sleep and sleep score; sleep coach and nap detection; Health Snapshot; hydration and women's health tracking; no ECG app	All-day heart rate, steps, sleep and intensity minutes.
Fitness features
Fitness features	Daily suggested running workouts and Garmin Coach plans; training effect and recovery time; wrist-based running dynamics and running power; PacePro; VO2 max and race predictions; pool and open-water swimming; running, cycling, strength, HIIT, yoga, Pilates, tennis, pickleball and padel profiles; point-to-point and breadcrumb course navigation, back-to-start and TracBack; no full offline maps or dedicated triathlon mode; no training readiness, load or status (Wareable and Tech Advisor)	Running, indoor running, cycling, pool swimming, skiing and rowing profiles; training status and load, aerobic and anaerobic training effect, VO2 max, recovery time and breadcrumb course guidance. Detailed running dynamics require an HRM strap or Running Dynamics Pod.
Safety features
Safety features	Incident detection during selected activities, assistance and LiveTrack require a paired compatible smartphone and connectivity; live event sharing is Android-only	–
Battery and connections
Battery life (maker's claim)
Battery life (maker's claim)	Up to 11 days	Up to 7 days
In low-power mode
In low-power mode	Up to 20 days	–
Mobile data option
Mobile data option	No	No
Works with
Works with	iPhone and Android	iPhone and Android
Storage
Storage	4 GB	–
Battery life detail
Battery life detail	Smartwatch up to 11 days; battery saver smartwatch up to 20 days; GPS-only up to 19 hours; all-systems GNSS up to 17 hours; actual life depends on display settings, enabled features and use	Up to seven days in smartwatch mode or five hours with GPS and music according to the exact model's Garmin Singapore specification table. Its prose also says 14 GPS hours without stating a music-use condition.
Charging
Charging	Garmin proprietary plug charging/data cable; rechargeable built-in battery	Rechargeable battery with Garmin charging cable.
Connectivity
Connectivity	Bluetooth and ANT+ ; controls smartphone music without offline playback; no Wi-Fi; Garmin Pay; Connect IQ apps, watch faces and data fields; smart notifications; Android-only text responses and notification images; Garmin Share and Garmin Messenger; no cellular connection or multi-band GNSS	Bluetooth, ANT+ and Wi-Fi; Garmin Pay, smart notifications, Connect IQ, LiveTrack and on-watch music playback to Bluetooth headphones.
Storage
Storage	4 GB memory/history ; standard model has no offline music player	Up to 500 songs and 200 hours of activity history.
Design
Weight (lightest version)
Weight (lightest version)	39 g (better)	42.2 g
Software
Software	Garmin	Garmin
Case materials
Case materials	Fibre-reinforced polymer bezel; chemically strengthened glass; silicone band; 5 ATM water rating	Stainless steel bezel, chemically strengthened glass and silicone band; 5 ATM water rating.
Size
Size	43 x 43 x 11.6 mm; Garmin lists 39 g without a separate body-only weight	42.5 x 42.5 x 13.5 mm; 42.2 g.
Bands
Bands	20 mm quick-release silicone bands; fits 126–203 mm wrists	Quick-release 20 mm band; fits wrists 127–204 mm.
Colours
Colours	Black/Slate Grey; Mist Grey/Whitestone	Black band and case with rose-gold hardware.
In the box
In the box	Forerunner 165; charging/data cable; documentation	–