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Garmin fēnix 5S vs Garmin Forerunner 645

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

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Garminfēnix 5SGarminForerunner 645
Overview
ReleasedMarch 20172018
Display
Case sizes42 mm42.5 mm
Panel–Memory-in-pixel
Always-on displayYesYes
Display detailAlways-on transflective colour Garmin Chroma display, 1.1 inches (27.94 mm), 218 × 218 pixels, with LED backlight and button controls.1.2-inch (30.4 mm) sunlight-readable transflective colour MIP display, 240 x 240 pixels, with five-button control.
Screen protection–Chemically strengthened glass.
Health and fitness
ECGNoNo
Blood oxygenNoNo
Skin temperatureNoNo
Sleep apnoea alertsNoNo
High blood pressure alertsNoNo
Body compositionNoNo
Fall detectionNoNo
Crash detectionNoNo
GPSSingle-bandSingle-band
Water resistance100 m50 m
SensorsGPS, GLONASS, Garmin Elevate optical wrist heart rate, barometric altimeter, three-axis compass, gyroscope, accelerometer and thermometer.GPS, GLONASS, Garmin Elevate wrist heart rate, barometric altimeter, compass, gyroscope, accelerometer and thermometer.
Health features–All-day heart rate, steps, sleep and intensity minutes.
Fitness featuresRunning, cycling, pool and open-water swimming, skiing, golf and paddle-sport profiles; training status, aerobic and anaerobic training effect, VO2 max estimates, recovery advice and race prediction. Additional running dynamics require a compatible chest strap.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 featuresCourse navigation, breadcrumb trails, TracBack and waypoint guidance; no preloaded detailed maps. Connected LiveTrack and GroupTrack require a paired phone.–
Battery and connections
Battery life (maker's claim)Up to 9 daysUp to 7 days
Mobile data optionNoNo
Works withiPhone and AndroidiPhone and Android
Battery life detailUp to nine days in smartwatch mode, twelve hours in GPS mode or twenty-eight hours in UltraTrac with wrist heart rate on, according to the Singapore specification; the European launch release quotes fourteen hours GPS and thirty-five hours UltraTrac.Up to seven days in smartwatch mode or 14 hours in GPS mode per the exact model's Garmin specification table. The same page's prose says 12 GPS hours; its table and headline say 14.
ChargingRechargeable lithium-ion battery with USB charging/data cable.Rechargeable battery with Garmin charging cable.
ConnectivityBluetooth and ANT+, smartphone notifications, Garmin Connect uploads, Connect IQ apps and phone music controls. Wi-Fi is included in Sapphire editions.Bluetooth, ANT+ and Wi-Fi; Garmin Pay, smart notifications, Connect IQ, LiveTrack and phone music controls. No on-watch music storage.
Storage64 MB total, with 37 MB available; up to 1,000 waypoints, thirty routes and 200 hours of activity data.Stores 200 hours of activity history.
Design
Weight (lightest version)67 g42.2 g
SoftwareGarminGarmin
Case materialsStainless-steel bezel, buttons and rear case; 10 ATM water rating. Sapphire-glass editions available.Stainless steel bezel, chemically strengthened glass and silicone band; 5 ATM water rating.
Size42 × 42 × 14.5 mm; 67 g with silicone band.42.5 x 42.5 x 13.5 mm; 42.2 g.
BandsQuickFit interchangeable bands.Quick-release 20 mm band; fits wrists 127–204 mm.
ColoursWhite model pictured; other case and band colours and Sapphire editions available.Black band with silver-toned bezel.

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