Perhaps the first thing you’ll notice about the Series 4 is its bigger display, which is up to 35 percent larger than the Series 3. Specifically comparing the larger 42mm Series 3 and 44mm Series 4 models, the Series 3 has a 740 sq mm display area while the Series 4 has a 977 sq mm display area. This means that the 44mm Series 4’s display is 32 percent larger than the 42mm Series 3.
Likewise for the smaller models, the 38mm Series 3 has a 563 sq mm display area, compared to the 40mm Series 4 with a 759 sq mm display area. This results in a 35 percent display size increase between generations. In essence, this means that the Series 4 packs more screen into what is nearly the same package as the Series 3, with slimmer bezels that are somewhat visually similar to the rounded corners of the iPhone X and iPhone XS.
The increased display area also results in increased resolution, with the 44mm Series 4 including 368×448 pixels, compared to 312×390 on the 42mm Series 3. The 40mm Series 4 has 324×394 pixels, while the 38mm Series 3 has 272×340 pixels. Thanks to all of these changes, app icons and fonts are now bigger and easier to read as well.
Although the display sizes have been increased, there are minimal changes to the actual size of the cases for Apple Watch Series 4, despite the new measurements. 38mm in Series 3 and prior has become 40mm, and 42mm in Series 3 and prior has become 44mm, with both of these numbers representing the height of the Apple Watch Series 4 case.
This is a change that shouldn’t be too noticeable, unless you’re comparing the Series 4 with a previous generation model side-by-side. And don’t worry about this update affecting your current band collection, as Apple made it clear during yesterday’s keynote that all previous Apple Watch bands will fit with the Series 4 case.
Looking at the thinness, Apple Watch Series 4 is just under 1mm slimmer compared to Series 3. Series 4 measures in at 10.7mm thin, compared to 11.4mm thin for Series 3.
As expected with an Apple update, the Series 4 has received a beefed up processor in the form of the 64-bit dual-core S4 processor.
Apple says that this is up to two times faster than the S3 processor found on the Series 3, enabling the Series 4 to be speedier when opening apps and performing other functions.
Exclusive to Apple Watch Series 4 are a collection of watch faces that take advantage of the enlarged displays to showcase as many as eight complications.
These complications have been enhanced to be more precise and provide more information, thanks to the increased display area.
There are also a few watch faces that will uniquely react to the edges of the Series 4’s display, like Vapor, Liquid Metal, and Fire and Water.
For the first time in a wearable device, you’ll be able to take a full ECG reading on Apple Watch Series 4. Using electrodes built into the Digital Crown and a new electrical heart rate sensor in the back crystal, an included ECG app will perform a reading when you touch the Digital Crown and hold it for 30 seconds.
The app can classify if your heart is beating in a normal pattern or if there are signs of Atrial Fibrillation, which could hint at potential health complications. You’ll be able to save your ECG recordings in the iOS Health app and create a PDF to share with your doctor. While Apple Watch has always been able to track your heart rate, the ECG app is a major update to Apple’s wearable line.
The ECG app will be added to Apple Watch Series 4 later this year, and will only be available to customers in the United States at launch.
Below you’ll find a quick list of features that are new and exclusive to Apple Watch Series 4, which are unavailable on Series 3 and prior devices. We’ve also listed everything that hasn’t changed further down, one notable constant being 18-hour battery life.
Changes between Series 3 and Series 4:
- Series 4 now includes haptic feedback on the Digital Crown
- The black ceramic and sapphire crystal back allows radio waves to easily pass through Series 4 for better cellular service
- The speaker on Series 4 is 50 percent louder
- Apple has relocated the microphone so that it reduces echo for better sound quality on the receiving end of phone calls
- With a new accelerometer and gyroscope, Series 4 can detect if you fall down and ask if emergency services should be alerted
- The improved accelerometer can measure up to 32 g-forces, increased from up to 16 g-forces on Series 3
- Series 4 has Apple’s new W3 wireless chip instead of the previous generation W2
- Connectivity improvements also include new Bluetooth 5.0, up from 4.2 on Series 3
- Now all models have 16GB storage capacities, instead of just GPS + Cellular on Series 3
No changes between Series 3 and Series 4:
- Built-in rechargeable lithium ion battery with an 18-hour battery life
- GPS, GLONASS, GALILEO, and GZSS
- LTE and UMTS on GPS + Cellular models
- 802.11b/g/n 2.4GHz Wi-Fi
- Barometric altimeter
- Water resistance up to 50 meters
- Optical heart sensor
- Ambient light sensor
- Force Touch
- Display with 1,000 nits brightness
- Magnetic charging cable and USB power adapter included
If you’re interested, Apple Watch Series 4 pre-orders will kick off at 12:01 a.m. PDT on September 14. Our pre-order post can help you figure out when pre-orders go up for you if you’re in a different time zone. We also went hands-on with Apple Watch Series 4 after yesterday’s “Gather Round” event, which you can read here.