Apple Watch Series 4 vs. Apple Watch Series 3

The all-new Apple Watch Series 4 is just hours from being available for pre-order, with orders opening on Apple.com at 12:01 a.m. PDT on September 14. If you're still on the fence about jumping to the new generation, this post should help you discern all of the pros and cons between sticking with your Apple Watch Series 3 or going with the upgraded Apple Watch Series 4.

Display

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.

apple watch series 4 flames
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 368x448 pixels, compared to 312x390 on the 42mm Series 3. The 40mm Series 4 has 324x394 pixels, while the 38mm Series 3 has 272x340 pixels. Thanks to all of these changes, app icons and fonts are now bigger and easier to read as well.

Case Size

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.

apple watch series 4 vs series 3
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.

apple watch series 3 vs series 4 thick
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.

Processor

apple watch s4As 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.

Watch Faces

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.

apple watch series4 gold stainless steel 09122018
These complications have been enhanced to be more precise and provide more information, thanks to the increased display area.

apple watch series 4 faces
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.

Health

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.

apple watch series4 ecg crown 09122018
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.

Tidbits

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
  • Second-generation optical heart sensor

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
  • 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.

Related Roundup: Apple Watch 11
Buyer's Guide: Apple Watch (Buy Now)

Popular Stories

Tim Cook WWDC 2018

Report: Tim Cook to Step Down as Apple CEO 'as Soon as Next Year'

Saturday November 15, 2025 2:40 pm PST by
Apple is preparing for Tim Cook to step down as CEO of the company "as soon as next year," according to the Financial Times. The company's board of directors and senior executives "recently intensified preparations for Cook to hand over the reins," the report said. While the report said that Apple is unlikely to name a new CEO before its next earnings report in late January, it went on to ...
iOS 26

Everything New in iOS 26.2 Beta 3

Monday November 17, 2025 3:20 pm PST by
Apple provided developers with the third beta of an upcoming iOS 26.2 update, and there are still new features that are being added with each beta that we get. We've rounded up all of the changes that Apple made in beta 3. AirDrop Apple added new AirDrop functionality, providing a way for two people to share files temporarily without having to add one another as contacts. iOS 26.2...
AirPods Pro Firmware Feature

Apple Releases New Firmware for AirPods Pro 2, AirPods Pro 3, and AirPods 4

Thursday November 13, 2025 11:35 am PST by
Apple today released new firmware designed for the AirPods Pro 3, the AirPods 4, and the prior-generation AirPods Pro 2. The AirPods Pro 3 firmware is 8B25, while the AirPods Pro 2 and AirPods 4 firmware is 8B21, all up from the prior 8A358 firmware released in October. There's no word on what's include in the updated firmware, but the AirPods Pro 2, AirPods 4 with ANC, and AirPods Pro 3...
applecare apple care banner

Apple Brings New AppleCare+ Options to India

Tuesday November 18, 2025 8:42 am PST by
Apple today announced an expansion of AppleCare+ coverage in India, with new options for monthly and annual plans, and the addition of Theft and Loss for iPhone for the first time. Options for monthly and annual AppleCare+ plans in India provide more choice and flexibility, allowing users to keep coverage for as long as they require. Apple's vice president of Worldwide iPhone Product...
best early black friday deals

Best Black Friday Apple Deals Live Now - Save on AirPods, iPads, and Apple Watches

Saturday November 15, 2025 1:45 pm PST by
We're officially in the month of Black Friday, which will take place on Friday, November 28 in 2025. As always, this will be the best time of the year to shop for great deals, including popular Apple products like AirPods, iPad, Apple Watch, and more. In this article, the majority of the discounts will be found on Amazon. Note: MacRumors is an affiliate partner with some of these vendors. When ...
Apple Wallet ID Illinois

iPhone Driver's License Feature Launching in Illinois

Tuesday November 18, 2025 8:47 am PST by
In select U.S. states, residents can add their driver's license or state ID to the Wallet app on the iPhone and Apple Watch, providing a convenient and contactless way to display proof of identity or age at select airports and businesses, and in select apps. Starting this Wednesday, November 19, the feature will be available to residents of Illinois. The announcement confirmed that the...
iPhone Pocket Short

iPhone Pocket Now Available to Order, But Already Selling Out

Friday November 14, 2025 6:20 am PST by
Apple recently teamed up with Japanese fashion brand ISSEY MIYAKE to create the iPhone Pocket, a limited-edition knitted accessory designed to carry an iPhone. iPhone Pocket is available to order on Apple's online store starting today, in the United States, France, China, Italy, Japan, Singapore, South Korea, and the United Kingdom. However, it is already completely sold out in the United...
apple silicon mac lineup 2024 feature purple m5

Apple's 2026 Mac Plans

Friday November 14, 2025 3:23 pm PST by
Most of Apple's Macs are slated to get M5 chips across 2026, and there's a possibility we'll even see the first M6 chips toward the end of the year. Updates are planned for everything from the MacBook Air to the Mac Studio. MacBook Air (Early 2026) The MacBook Air will be one of the first Macs to get a 2026 refresh, with an update planned for the first few months of the year. The MacBook...
CarPlay Liquid Glass Dark

Here's When Tesla is Expected to Add Support for Apple CarPlay

Sunday November 16, 2025 6:49 am PST by
In his Power On newsletter today, Bloomberg's Mark Gurman reiterated that Tesla plans to add Apple CarPlay support to its vehicles "in the coming months." This is easily the biggest news for the regular version of CarPlay in years, should Tesla actually follow through with offering the system in its vehicles. As noted by Gurman, this would be a stunning reversal for Tesla and its CEO Elon ...
tvOS 26 Profiles

tvOS 26.2 Adds a Useful New Feature to Your Apple TV

Friday November 14, 2025 10:02 am PST by
Starting with the upcoming tvOS 26.2 update, currently in beta, additional profiles created on the Apple TV no longer require their own Apple Account. In the Settings app on the Apple TV, under Profiles and Accounts, anyone can create a new profile by simply entering a name and indicating whether the profile is for a kid. The profile will be associated with the primary user's Apple Account,...

Top Rated Comments

pbaker103 Avatar
94 months ago
This will be a huge upgrade for me coming from my Series 0
Score: 12 Votes (Like | Disagree)
aolbites Avatar
94 months ago
I'd rather have a thicker case if it meant improved battery life.

Seriously, I mean the Series 4 has 1 hour less talk time than Series 3. It was bad enough when Apple was stagnating, but now it's going backwards.
Score: 7 Votes (Like | Disagree)
snej Avatar
94 months ago
A maybe noteworthy detail is that the Series 4 is still 0.2mm thicker than the Series 1 and 1st generation Apple Watch.
Score: 7 Votes (Like | Disagree)
Agit21 Avatar
94 months ago
They didnt increase battery life which is sad. Going to wait for series 5.
Score: 6 Votes (Like | Disagree)
johnyslats Avatar
94 months ago
12 hours to go. Hyped!
Score: 6 Votes (Like | Disagree)
Sasparilla Avatar
94 months ago
Nice overview, thanks. While the 4 is more capable, for folks that don't have one yet, that 3 starting price point is awesome....the 3 is a great watch.
Score: 4 Votes (Like | Disagree)