Fitbit Charge 2Apple Watch Series 2
Tech specs 
SizeWidth: 21mm
Small: 14 cm - 17 cm in circumference
Large: 16.5 cm - 20.6 cm in circumference
XL: 20.6 cm - 23.6 cm in circumference
38.6mm x 33.3mm x 10.5mm (H x W x D)
32.0mm x 35.9mm x 10.5mm (H x W x D)
MaterialStainless steel casing, elastomer strapSteel, Aluminum, Ceramic, Sapphire Crystal
ChargingUSB. inductive charging
BatteryLithium-polymerLithium-ion
Battery lifeup to 5 days18+ hours
Water-resistanceSweat, rain and splash proof.5 ATM (50 metres)
Weight36 grams25 grams to 69 grams depending on the model
SensorOptical heart rate tracker, 3-axis accelerometer, altimeter, vibration motorAmbient light, Heart rate sensor, accelerometer, gyroscope, built-in gps.
DisplayOLEDOLED Retina display with Force Touch
Ion-X glass (strengthened glass)
Screen size3.8 cm38mm: 340x272 pixels
42mm: 390x312 pixels
ColorsBlack, Plum, Blue, Teal, Lavender Rose Gold, Black/Gunmetal Gold, Rose Gold, Space Gray, Silver, Black. Straps vary by editions.
OtherPLATFORM: watchOS
PROCESSOR: Apple S2, dual-core
MEMORY: 512 RAM, 8GB storage (2GB of which can be used for music)
CONNECTIVITY: Bluetooth 4.0, NFC, WiFi
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYes
SleepYes
Heart rate24/7Yes
Stress & recovery
Pulse Ox
Respiration rate
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPSYes
Running featuresWatch displays up to 5 metrics during your run (time, distance, current pace and average pace, heart rate, active calories or total calories).
Swimming featuresPool swim and open water swim. At the end of a swim, the watch displays the time of day the activity took place, dominant stroke used (auto-detection is used), distance, workout time, pool length, laps completed, average pace, average heart rate, and both active and total calories burned, as well as the weather at your location.
Other Guided breathing
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storageYes
Connected payYes
LTE
Links 
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