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 10

Popular Stories

iPhone 17 Pro on Desk Centered 1

iPhone 17 Pro Launching Next Month With These 12 New Features

Wednesday August 20, 2025 1:23 pm PDT by
Apple's iPhone 17 Pro and iPhone 17 Pro Max should be unveiled in a few more weeks, and there are plenty of rumors about the devices. Below, we recap key changes rumored for the iPhone 17 Pro models: Aluminum frame: iPhone 17 Pro models are rumored to have an aluminum frame, whereas the iPhone 15 Pro and iPhone 16 Pro models have a titanium frame, and the iPhone X through iPhone 14 Pro...
Apple Watch Ultra 2 Complications

Apple Watch Ultra 3 Just Weeks Away: Eight Reasons to Upgrade

Wednesday August 20, 2025 6:44 am PDT by
We're only weeks away from Apple's annual iPhone event – rumored to take place on September 9 – and along with the new iPhone 17 series, we're going to get a new version of the Apple Watch Ultra for the first time since 2023. By the time the Ultra 3 is unveiled, it will have been two years since the previous model arrived. The intervening period has left plenty of room for enhancements,...
apple wallet drivers license feature iPhone 15 pro

iPhone Driver's Licenses in Apple Wallet Now Available in 10 U.S. States

Wednesday August 20, 2025 12:00 pm PDT 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. This week, Apple announced the 10th U.S. state that has implemented the feature: Montana. Below, we have recapped key details about...
iPhone 17 Pro Dark Blue and Orange

When Is iPhone 17 Coming Out?

Wednesday August 20, 2025 5:00 am PDT by
Apple's iPhone 17 series is expected to debut in September 2025. This release follows Apple's recent trend of introducing new iPhone models annually in the fall. To unveil the iPhone 17, iPhone 17 Air, iPhone 17 Pro, and iPhone 17 Pro Max, Apple is expected to hold its annual iPhone announcement event during the week of September 8, 2025, with September 9 or 10 emerging as the most likely...
Apple TV Plus Feature 2 Dark Teal

Apple TV+ Price Increase Announced

Thursday August 21, 2025 7:26 am PDT by
Apple today raised the monthly price of its Apple TV+ streaming service to $12.99 in the U.S., according to 9to5Mac's Benjamin Mayo. Apple TV+ cost just $4.99 per month in the U.S. when it launched in 2019, but the price has now increased three times. The price went up to $6.99 per month in 2022, and then to $9.99 per month in 2023, and now the service costs $12.99 per month. The latest...
techwoven cases 1

Colors for Alleged 'TechWoven' iPhone 17 Cases Shown Off in New Images

Thursday August 21, 2025 2:33 pm PDT by
Apple is designing new "TechWoven" cases for the iPhone 17, with photos of some of the alleged case colors shared today by leaker Majin Bu. The cases feature a muted, fabric design in colors that appear to include black, blue, green, purple, and orange. The TechWoven cases will reportedly replace the fabric-like FineWoven casesthat Apple discontinued with the iPhone 16 launch. The FineWoven...

Top Rated Comments

pbaker103 Avatar
91 months ago
This will be a huge upgrade for me coming from my Series 0
Score: 12 Votes (Like | Disagree)
aolbites Avatar
91 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
91 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
91 months ago
They didnt increase battery life which is sad. Going to wait for series 5.
Score: 6 Votes (Like | Disagree)
johnyslats Avatar
91 months ago
12 hours to go. Hyped!
Score: 6 Votes (Like | Disagree)
Sasparilla Avatar
91 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)