Garmin Forerunner 170 Music vs Garmin Forerunner 645 Music

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Forerunner 170 Music compared with Forerunner 645 Music

	GarminForerunner 170 Music	GarminForerunner 645 Music
Overview
Released
Released	May 2026	2018
Display
Case sizes
Case sizes	42.6 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 and large-font setting; 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; gyroscope; accelerometer; thermometer; ambient light sensor; thermometer measures activity/ambient temperature, not overnight skin temperature	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 and respiration; advanced sleep, sleep coach, breathing variations and nap detection; meditation; smart wake alarm; Health Snapshot; lifestyle logging; Health Status; women's health tracking via Garmin Connect; no ECG app	All-day heart rate, steps, sleep and intensity minutes.
Fitness features
Fitness features	More than 80 sports apps; training readiness, status, load, load focus and recovery time; Garmin running, cycling and strength coaching; daily suggested running workouts and quick workouts; wrist-based running dynamics and running power; ground-contact balance requires a compatible accessory; PacePro and grade-adjusted pace; VO2 max and race predictions; cycling power-meter and Varia radar/light support; pool and open-water swimming; no dedicated triathlon mode; Breadcrumb course navigation, point-to-point navigation, back-to-start and TracBack; elevation profile, future elevation plot and Up Ahead; no full routable offline maps	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; live event sharing is Android-only; screen flashlight, not a separate LED torch	–
Battery and connections
Battery life (maker's claim)
Battery life (maker's claim)	Up to 10 days	Up to 7 days
In low-power mode
In low-power mode	Up to 19 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 10 days, or 4 days with display always on; battery saver smartwatch up to 19 days; GPS-only GNSS up to 20 hours; all-systems GNSS up to 14 hours; with music, GPS-only up to 7.5 hours and all-systems up to 6.5 hours (exact series manual; UK web table mislabels 7.5 hours as days); actual life depends on enabled features and usage	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 lithium-ion battery; USB charging temperature 0–45 °C	Rechargeable battery with Garmin charging cable.
Connectivity
Connectivity	Bluetooth, ANT+ and Wi-Fi; GPS, GLONASS and Galileo; no multi-band GNSS; Garmin Pay contactless payments; Android-only text responses and notification images; Connect IQ apps/watch faces/data fields; Garmin Share; controls smartphone music and plays downloaded personal audio or supported music-service content through compatible Bluetooth headphones; third-party services may require subscriptions; no speaker/microphone calls or cellular connection	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 with offline music support	Up to 500 songs and 200 hours of activity history.
Design
Weight (lightest version)
Weight (lightest version)	41 g (better)	42.2 g
Software
Software	Garmin	Garmin
Case materials
Case materials	Fibre-reinforced polymer bezel; silicone band; chemically strengthened glass; 5 ATM water rating; operating/storage temperature –20–60 °C	Stainless steel bezel, chemically strengthened glass and silicone band; 5 ATM water rating.
Size
Size	42.6 x 42.6 x 11.9 mm; Garmin lists 41 g without a separate body-only weight	42.5 x 42.5 x 13.5 mm; 42.2 g.
Bands
Bands	Standard 20 mm quick-release two-tone silicone band; fits 126–203 mm wrists	Quick-release 20 mm band; fits wrists 127–204 mm.
Colours
Colours	Black with Black/Amp Yellow band; Whitestone with Whitestone/Cloud Blue band; Teal Green with Teal Green/Citron band; Red Pink with Red Pink/Mango band	Black band and case with rose-gold hardware.
In the box
In the box	Forerunner 170 Music; charging cable; documentation	–