Apple Watch Series 3Apple Watch Series 4
Tech specs 
Size38.6mm x 33.3mm x 10.7mm (H x W x D)
32.0mm x 35.9mm x 10.7mm (H x W x D)
40 mm (band fits 130-200mm wrists)
44 mm (band fits 140-210mm wrists)
MaterialAluminum, Ceramic (White, Black), Sapphire Crystal, Gold Aluminium, Stainless Steel (Silver, Black)Sapphire crystal and ceramic back.
Chargingwireless chargingWireless charging
BatteryLithium-ionLithium-ion
Battery life18+ hours18+ hours
Water-resistance5 ATM (50 metres)5 ATM (50 metres)
Weight53 gramsCase weight: 30.1g (for 40mm version); 36.7g (for 44mm version)
SensorAmbient light, heart rate sensor, accelerometer, gyroscope, GPS, barometric altimeterAmbient light, optical heart rate sensor, Electrical heart sensor, improved accelerometer up to 32 g‑forces, improved gyroscope, GPS (GLONASS, Galileo, and QZSS), barometric altimeter, ambient light sensor
DisplayOLED Retina display with Force Touch
Ion-X glass (strengthened glass)
LTPO OLED Retina display with Force Touch (1000 nits), Ion-X strengthened glass
Screen size38mm: 340x272 pixels
42mm: 390x312 pixels
44mm: 977 sq mm display area (368 x 448 pixel resolution)
40mm: 759 sq mm display area (324 x 394 pixel resolution)
ColorsGold, Rose Gold, Space Gray, Silver, Black. Straps vary by editions.A number of aluminum finishes anodized in silver, gold and space gray. You can also pick up the device in gold stainless steel with a matching Milanese band, joining the silver and space black stainless steel models.
OtherPLATFORM: watchOS
PROCESSOR: S3 dual-core processor
MEMORY: 512 RAM, 16GB storage
CONNECTIVITY: Bluetooth 4.0, NFC, WiFi, LTE and UMTS cellular radio
PLATFORM: watchOS
PROCESSOR: S4 with 64-bit dual-core processor, W3 Apple wireless chip
MEMORY: 512 RAM, 16GB storage
CONNECTIVITY: Bluetooth 4.0, NFC, WiFi, LTE and UMTS cellular radio
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYesYes
Sleep
Heart rateYesYes
Stress & recovery
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSYesYes (GPS,GLONASS, Galileo, and QZSS)
Running featuresWatch displays up to 5 metrics during your run (time, distance, current pace and average pace, heart rate, active calories or total calories).Watch 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. Pool 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
- ECG monitor
- irregular heart rate detection
- low or high heart rate alerts
- fall detection
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storageYes ( Stream Apple Music direct to watch)Yes (Stream Apple Music direct to watch)
Connected payYesYes
LTEYesYes
Links 
Affiliate link*AmazonAmazon
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