| Apple Watch Series 4 | Fitbit Charge 3 | |
 |  | |
| Tech specs | ||
| Size | 40 mm (band fits 130-200mm wrists) 44 mm (band fits 140-210mm wrists) | Device Dimensions: 35.8mm x 22.7mm x 11.8 One size (small and large bands included) |
| Material | Sapphire crystal and ceramic back. | 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. |
| Charging | Wireless charging | USB |
| Battery | Lithium-ion | Lithium-polymer |
| Battery life | 18+ hours | up to 7 days |
| Water-resistance | 5 ATM (50 metres) | 5 ATM |
| Weight | Case weight: 30.1g (for 40mm version); 36.7g (for 44mm version) | 29 grams |
| Sensor | Ambient 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 | Optical heart rate tracker, 3-axis accelerometer, altimeter, SpO2, vibration motor |
| Display | LTPO OLED Retina display with Force Touch (1000 nits), Ion-X strengthened glass | OLED full touchscreen, TFT |
| Screen size | 44mm: 977 sq mm display area (368 x 448 pixel resolution) 40mm: 759 sq mm display area (324 x 394 pixel resolution) | 35.8mm x 22.7mm |
| Colors | 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. | Multiple |
| Other | 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 | NFC (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 | ||
| Steps | Yes | Yes |
| Distance | Yes | Yes |
| Calories burned | Yes | Yes |
| Activity | Yes | Yes |
| Floors | Yes | Yes |
| Sleep | Yes | Yes |
| Heart rate | Yes | 24/7 + HRV (premium subscription) |
| Stress & recovery | ||
| Pulse Ox | Yes | |
| Respiration rate | Yes (premium subscription) | |
| UV exposure | ||
| Skin temperature | ||
| Galvanic skin response | ||
| Hydration level | ||
| Calorie intake | ||
| GPS | Yes (GPS,GLONASS, Galileo, and QZSS) | Connected GPS |
| Running features | Watch displays up to 5 metrics during your run (time, distance, current pace and average pace, heart rate, active calories or total calories). | |
| Swimming features | 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 | Guided breathing, Female Health Tracking |
| Non-fitness functions | ||
| Smartphone notifications | Yes | Yes |
| On-board music storage | Yes (Stream Apple Music direct to watch) | |
| Connected pay | Yes | Yes (special edition) |
| LTE | Yes | |
| Links | ||
| Affiliate link* | Amazon | Amazon |
| Read more | Article | Review |
**All tech specs and images on this page come from manufacturers. These may change over time as manufacturers sometimes update their devices. While we cannot guarantee absolute accuracy of information on this page, we promise to review this content regularly and do our best to bring you the most up-to-date information. To be absolutely sure of tech specs of a particular device, we recommend checking the manufacturer’s website.