Fitbit Charge 2Fitbit Charge 3Fitbit Charge 4
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
Device Dimensions: 35.8mm x 22.7mm x 11.8
One size (small and large bands included)
Device Dimensions: 42.7mm x 28.8mm x 12.5mm
One size (small and large bands included)
MaterialStainless steel casing, elastomer strapBuilt 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.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.
ChargingUSB. USBUSB
BatteryLithium-polymerLithium-polymerLithium-polymer
Battery lifeup to 5 daysup to 7 daysup to 7 days, or up to 5 hours with GPS.
Water-resistanceSweat, rain and splash proof.5 ATM5 ATM
Weight36 grams29 grams30 grams
SensorOptical heart rate tracker, 3-axis accelerometer, altimeter, vibration motorOptical heart rate tracker, 3-axis accelerometer, altimeter, SpO2, vibration motor3-axis accelerometer, Optical heart rate monitor, Pulse Ox, GPS, Vibration motor, NFC chip for Fitbit Pay, Altimeter, Bluetooth LE (BLE)
DisplayOLEDOLED full touchscreen, TFTOLED full touchscreen, TFT
Screen size3.8 cm35.8mm x 22.7mm35.8mm x 22.7mm
ColorsBlack, Plum, Blue, Teal, Lavender Rose Gold, Black/Gunmetal MultipleMultiple
OtherNFC (Special edition)
Connectivity: Bluetooth, WiFi
Charge 3 stores your stats and data for 7 days in between the times you sync your tracker.
Charge 4 stores your stats and data for 7 days in between the times you sync your tracker.
Activity tracking 
StepsYesYesYes
DistanceYesYesYes
Calories burnedYesYesYes
ActivityYesYesYes
FloorsYesYesYes
SleepYesYesYes
Heart rate24/724/724/7
Stress & recovery
Pulse OxYesYes
Respiration rate
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPSConnected GPSYes
Running features
Swimming features
Other Guided breathingGuided breathing, Female Health TrackingGuided breathing, Female Health Tracking, Spotify control
Non-fitness functions 
Smartphone notificationsYesYesYes
On-board music storage
Connected payYes (special edition)Yes
LTE
Links 
Affiliate link*AmazonAmazonAmazon
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