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

hikawa phone grip stand apple%402x

Apple Launches Second Limited-Edition iPhone Accessory in a Month

Friday November 21, 2025 3:53 am PST by
Apple has begun selling the Hikawa Phone Grip and Stand, a new limited-edition iPhone accessory designed with accessibility in mind. Designed by LA-based Bailey Hikawa to celebrate the 40th anniversary of accessibility at Apple, the grip uses magnets to securely snap onto any iPhone with MagSafe. Apple says it can be removed with ease, and doubles as a stand with two different viewing...
iOS 26

iOS 26.2 Adds These New Features to Your iPhone

Thursday November 20, 2025 10:50 am PST by
iOS 26.2 is currently in beta testing. The upcoming update includes a handful of new features and changes on the iPhone, including a new Liquid Glass slider for the Lock Screen's clock, offline lyrics for Apple Music, and more. In a recent press release, Apple confirmed that iOS 26.2 will be released to all users in December, but it did not provide a specific release date. Keep reading...
Apple Shopping Event 2025

Apple Announces 2025 Black Friday Event, Here's What You Can Get

Thursday November 20, 2025 6:28 am PST by
Apple's annual four-day Black Friday through Cyber Monday shopping event is returning on Friday, November 28 through Monday, December 1 in many countries, including the United States, Canada, Australia, New Zealand, France, Germany, Italy, Spain, the United Kingdom, Belgium, the Netherlands, Sweden, Thailand, and others. During the shopping event, customers can get an Apple gift card with...
iOS 26 on Three iPhones

iOS 27 Will Reportedly Have Two Key Upgrades

Sunday November 23, 2025 8:48 am PST by
iOS 27 will reportedly have two major elements: quality improvements and new AI features. In his Power On newsletter today, Bloomberg's Mark Gurman said that iOS 27 will be similar to Mac OS X Snow Leopard, in the sense that Apple is focused on improving "quality and underlying performance" over adding new features. Gurman said there is one exception to this rule, though, as he expects...
maxresdefault

The MacRumors Show: iPhone 18 Pro Looks Like a Huge Upgrade

Friday November 21, 2025 9:10 am PST by
On this week's episode of The MacRumors Show, we talk through all of the new features and improvements expected to come to next year's iPhone 18 Pro and iPhone 18 Pro Max models. Subscribe to The MacRumors Show YouTube channel for more videos Apple's next-generation iPhones are less than ten months away and we already have a good idea about what to expect based on corroborated leaks, rumors,...
Apple Foldable Thumb

Foldable iPhone to Debut These Two Breakthrough Features

Wednesday November 19, 2025 7:26 am PST by
Apple's first foldable iPhone is expected to launch alongside the iPhone 18 Pro models in fall 2026, and it's shaping up to include two standout features that could set it apart from the competition. The book-style foldable will reportedly feature an industry-first 24-megapixel under-display camera built into the inner display, according to a recent JP Morgan equity research report. That...
General Black Friday Deals 25 Red

Apple Black Friday Deals Available Now on AirPods, iPads, Accessories, and More

Friday November 21, 2025 8:48 am PST by
We're only a few days away from 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...
ipad black friday 2025

The Best Early Black Friday iPad Deals

Thursday November 20, 2025 10:20 am PST by
Black Friday is just over a week away, and iPad deals have finally started to flood in at retailers like Amazon and Best Buy. Below we're tracking discounts on every current generation iPad, including lowest-ever prices on M3 iPad Air and M5 iPad Pro, plus steep markdowns on iPad and iPad mini. Note: MacRumors is an affiliate partner with some of these vendors. When you click a link and make a ...
iPhone 17 Pro Cosmic Orange

10 Reasons to Wait for Next Year's iPhone 18 Pro

Wednesday November 19, 2025 4:00 am PST by
Apple's iPhone development roadmap runs several years into the future and the company is continually working with suppliers on several successive iPhone models at the same time, which is why we often get rumored features months ahead of launch. The iPhone 18 series is no different, and we already have a good idea of what to expect for the iPhone 18 Pro and iPhone 18 Pro Max. One thing worth...

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)