Fitbit Alta HRFitbit Charge 3
Tech specs 
SizeDevice Dimensions: 15 mm x 10 mm x 35 mm (W x D x L)
(Sizes depend on type of band)
Device Dimensions: 35.8mm x 22.7mm x 11.8
One size (small and large bands included)
MaterialWristband is made of a flexible, durable elastomer. The tracker is made with surgical-grade stainless steel, and the buckle is made with aluminum.Built of more lightweight material including an aerospace grade aluminum case and Corning Gorilla Glass 3 display. The housing and buckle are made of anodized aluminum.
ChargingUSBUSB
BatteryLithium-polymerLithium-polymer
Battery lifeup to 7 daysup to 7 days
Water-resistanceSweat, rain and splash proof5 ATM
Weight15 grams29 grams
Sensor3-axis accelerometer, Vibration motor, optical heart rate sensorOptical heart rate tracker, 3-axis accelerometer, altimeter, SpO2, vibration motor
DisplayB&W OLED touchscreenOLED full touchscreen, TFT
Screen size1.4-inch, 128 x 36 pixel resolution35.8mm x 22.7mm
ColorsBlack, Blue/Gray, Coral, FuchsiaMultiple
OtherNFC (Special edition)
Connectivity: Bluetooth, WiFi
Charge 3 stores your stats and data for 7 days in between the times you sync your tracker.
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYes
SleepYesYes
Heart rate24/724/7 + HRV (premium subscription)
Stress & recovery
Pulse OxYes
Respiration rateYes (premium subscription)
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPS
Running features
Swimming features
Other Clock, auto sleep detection, silent wake alarm, auto exercise recognition.Guided breathing, Female Health Tracking
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storage
Connected payYes (special edition)
LTE
Links 
Affiliate link*Amazon | FitbitAmazon | Fitbit
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