Choosing between the Apple Watch 3 and Apple Watch 4 is a decision about whether newer sensors, a larger display, and modest performance gains justify the step up from an earlier-generation device. This comparison focuses on the key differences that remain relevant after years of software updates and product cycles. Both watches remain capable daily drivers for fitness tracking, notifications, and wearables-first experiences, but they differ in meaningful ways. The following breakdown highlights hardware, health, and usability factors to consider when deciding which used or refurbished device best fits your needs.
Design and display
At a glance, the most visible difference between the Apple Watch 3 and Apple Watch 4 is the display size and aspect ratio. The Apple Watch 4 adopts a taller 40 mm and 44 mm case with a slightly larger screen area that reaches closer to the edges, while the Apple Watch 3 uses the previous 38 mm and 42 mm sizes with a more traditional screen border. The Apple Watch 4 also introduces a back crystal that sits slightly differently, contributing to a redesigned look and feel on the wrist. The display on the Apple Watch 4 is slightly brighter and uses LTPO-like optimization in software, making outdoor readability noticeably better, while the Apple Watch 3 display remains clear but better suited to indoor use.
Size and comfort differences
The shift to a taller display on the Apple Watch 4 makes a subtle but meaningful difference in screen real estate for reading notifications and using apps. However, some users with smaller wrists may find the larger 44 mm case less comfortable than the compact 38 mm Apple Watch 3. Fit is not only about width but also thickness; the Apple Watch 4 is marginally thicker due to new sensor components, which can affect strap clearance on some bands. If you already use a case or screen protector, the added bulk on the Apple Watch 4 is worth checking against your typical band setup before choosing it over the more compact Apple Watch 3.
Performance and processor
Under the hood, the Apple Watch 3 uses an S3 SiP combined with the Apple-designed dual-core chip, while the Apple Watch 4 upgrades to the S4 SiP with a faster 64-bit dual-core processor and improved GPU. In practice, the Apple Watch 4 feels snappier when opening apps, scrolling through lists, and navigating the watch face, especially when multiple complications or widgets are active. The Apple Watch 3 remains responsive for core tasks like checking the time, receiving notifications, and tracking workouts, but heavier app usage and watch faces with richer graphics may highlight the generational gap in processing power.
Benchmark and real-world feel
While official numbers are rarely published for these ultra-mobile devices, user-reported experiences and long-term reviews consistently show the Apple Watch 4 as offering smoother interactions when launching apps and switching contexts. The built-in GPS on both models performs well, but the Apple Watch 4 benefits from enhanced algorithms that can lead to quicker satellite fixes and steadier tracking during exercise. If your daily use involves frequent app interactions, third-party watch faces, or complex complications, the Apple Watch 4 tends to deliver a noticeably smoother experience than the Apple Watch 3.
| Attribute | Apple Watch 3 | Apple Watch 4 | Source Type |
|---|---|---|---|
| Display size | 38 mm or 42 mm | 40 mm or 44 mm | Manufacturer specifications |
| Processor | S3 SiP with dual-core CPU | S4 SiP with 64-bit dual-core CPU | Manufacturer teardowns and benchmarks |
| Typical battery (usage) | ~18–24 hours | ~18–24 hours | User reviews and lab tests |
| Barometer | No | Yes | Teardowns and spec sheets |
| Always-on sensor capability | Limited, dimming only | Enhanced sensor suite | Technical reviews |
| Built-in GPS | Yes | Yes with improved lock | Manufacturer and independent tests |
Health and sensors
The Apple Watch 4 introduced meaningful sensor upgrades that the Apple Watch 3 lacks, most notably an optical barometer for elevation tracking and an improved heart rate sensor with faster irregular rhythm notifications. These additions make the Apple Watch 4 more useful for hikers who want floor climb estimates and for users who want earlier alerts about potential heart rhythm concerns. The Apple Watch 3 remains capable for basic heart rate tracking, workout detection, and stand reminders, but it does not include the electrical and optical sensors that enable the advanced irregular rhythm and fall detection features introduced later in the Apple Watch line.
Health feature comparison
Both watches support on-demand ECG in regions where cleared, SpO2 background measurements, and robust activity tracking with move time, exercise, and stand rings. The Apple Watch 4 adds value with its barometer-derived elevation data, which can enrich workouts recorded on trails or stairs and improve floor counting in homes. For users who prioritize health metrics and want longer-term trend accuracy, the Apple Watch 4 offers more built-in insights out of the box, while the Apple Watch 3 continues to provide reliable baseline measurements for heart rate and workout detection.
Battery and charging
Battery life on both the Apple Watch 3 and Apple Watch 4 is broadly similar under typical usage, with most users seeing around 18 to 24 hours between charges depending on feature usage and app activity. The Apple Watch 4 does not introduce a larger physical battery, but software optimizations tied to the S4 chip and the LTPO-inspired display adjustments help maintain endurance. Fast charging is supported on both, offering a convenient boost when needed. If battery longevity is your primary concern, consider how your usage patterns—screen-on time, workout frequency, and notification volume—affect daily charging more than the model difference itself.
Software and long-term support
Both the Apple Watch 3 and Apple Watch 4 receive ongoing watchOS updates for several years after release, but support timelines differ. The Apple Watch 4 has a longer remaining support window in practice, which can be an important factor if you plan to keep a device for multiple years. When comparing Apple Watch 3 vs Apple Watch 4 from a future-proofing standpoint, the Apple Watch 4 generally offers more headroom for new features, app optimizations, and security updates. That said, the Apple Watch 3 remains functional for everyday tasks and will continue to receive critical updates for as long as Apple supports its older hardware tier.
Which should you choose
If your priority is compact sizing, basic fitness tracking, and cost efficiency, the Apple Watch 3 remains a sensible choice, especially as a secondary or backup device. If you value a larger, brighter display, built-in barometer for elevation tracking, improved sensor capabilities for health insights, and smoother day-to-day performance, the Apple Watch 4 is the stronger long-term pick. Consider your wrist size, preferred feature set, and how long you intend to use the device before upgrading. For most users planning to keep a watch for several years, the Apple Watch 4 offers durability and features that better age than the earlier generation hardware.