Comparison · Fitness watches · Desk research
Apple Watch Series 4 vs Apple Watch Series 5
Quick Answer
Series 4 (2018) and Series 5 (2019) are the same 40mm / 44mm size class with the same 324×394 and 368×448 pixel grids at 1000 nits, 50m water resistance, ECG, and Apple’s 18-hour battery claim. Series 4 Support lists an LTPO OLED with Force Touch (Always-On not listed) and 16GB on the S4. Series 5 Support lists Always-On Retina LTPO OLED with Force Touch, the S5 SiP, 32GB, and a compass; Apple’s 10 September 2019 Newsroom frames Always-On and the.
The verdict
Apple Watch Series 4 or Apple Watch Series 5 — quote the two manufacturer sheets.
Why: The story is not a new case size. Series 5 (2019) debuted Always-On Retina, added a built-in compass, and doubled on-device storage to 32GB versus Series 4’s 16GB Force Touch display (Always-On not listed). Both share the 40/44mm 324×394 / 368×448 grid, 1000 nits, 18-hour claims, 50m, and ECG. Both sit off Apple’s watchOS 27 list. Quote Apple.
Buy Apple Watch Series 4 if
You already wear Series 4, ECG plus 50m swimproof still cover what you do, and you do not need Always-On, a compass, or 32GB.
Buy Apple Watch Series 5 if
You specifically want the first Always-On Apple Watch plus compass and 32GB in the same 40/44mm size class as Series 4, and you accept that Series 5 is also off Apple’s watchOS 27 list.
Spec comparison
OEM rows only. Series 4 numbers are from Apple Support 111984. Series 5 numbers are from Apple Support 118453. Always-On / compass debut copy also cites Apple’s 10 September 2019 Newsroom post. Cells Apple does not publish stay marked.
| Spec | Series 4 | Series 5 |
|---|---|---|
| Year introduced | 2018 (Newsroom 12 September 2018) | 2019 (Newsroom 10 September 2019) |
| Case size(s) | 40mm and 44mm | 40mm and 44mm |
| Case material | Aluminum or stainless steel | Aluminum, stainless steel, titanium, or ceramic |
| Dimensions (44mm) | 44 × 38 × 10.7mm | 44 × 38 × 10.74mm |
| Display | LTPO OLED Retina with Force Touch; 40mm 324×394; 44mm 368×448; 1000 nits. Always-On not listed | Always-On Retina LTPO OLED with Force Touch; same 324×394 / 368×448 grid; 1000 nits |
| Chip / storage | S4, 64-bit dual-core; 16GB | S5 SiP, 64-bit dual-core; 32GB |
| Battery — normal use | Up to 18 hours (Apple test, August 2018) | Up to 18 hours (Apple test, August 2019) |
| Fast charge (OEM) | Magnetic charging cable; no 15-minute / 80% figures | Magnetic charging cable; no 15-minute / 80% figures |
| Weight (aluminum examples) | 40mm 30.1g; 44mm 36.7g | 40mm 30.8g; 44mm 36.5g |
| Wireless | Bluetooth 5.0; Wi-Fi 802.11b/g/n 2.4GHz | Bluetooth 5.0; Wi-Fi 802.11b/g/n 2.4GHz |
| GNSS | GPS, GLONASS, Galileo, and QZSS | GPS/GNSS (constellation list not itemized on Support 118453) |
| Compass | Not listed | Compass |
| Water | 50m (ISO 22810:2010) | 50m (ISO 22810:2010) |
| Heart rate | Electrical + optical heart sensor | Electrical + second-generation optical heart sensor |
| ECG | ECG debut (Newsroom 2018) | Electrical heart sensor (ECG class; Series 4+) |
| Fall Detection | Not labeled on Support 111984 (2018 Newsroom launch copy described fall detection hardware) | Accelerometer up to 32 g-forces with fall detection |
| International emergency calling | Not listed on Support 111984 | Listed for GPS + Cellular |
| OS / phone (as printed) | iPhone 6 or later + iOS 12 (cellular); iPhone 5s or later + iOS 12 (GPS) | iPhone 6s or later with iOS 13 or later |
| watchOS 27 (Apple list) | Not named | Not named |
| US start (dated) | Discontinued; no street price treated as fact | Discontinued; no street price treated as fact |
Who each watch is for
Series 4 is the ECG-debut everyday Apple Watch. If you already wear it, the Support-page delta to Series 5 is Always-On, compass, 32GB, and the S5 SiP — not a larger display grid.
Series 5 is the first Always-On Apple Watch. Apple’s 2019 Newsroom copy is the display that “never sleeps,” plus a built-in compass. Storage doubles to 32GB. It is still a 40/44mm watch with the same pixel counts as Series 4, still 18 hours as Apple tested in August 2019, still 50m, still ECG.
Always-On, compass, and 32GB
That is the pair. Series 4 Force Touch without Always-On and 16GB versus Series 5 Always-On (Force Touch remains listed) plus compass and 32GB. Do not invent a resolution bump. Do not invent dual-frequency GPS on either side.
watchOS 27 — quote Apple
Series 12 Newsroom, 9 September 2026: “watchOS 27 will be available for Apple Watch Series 9 or later, Apple Watch SE 3, and Apple Watch Ultra 2 or later … and requires iPhone 11 or later or iPhone SE (2nd generation or later) with iOS 27 or later.” Series 4 and Series 5 are not on that sentence.
Battery
Copy Apple’s mode names. Both Support pages: up to 18 hours. Series 4 footnote: August 2018 test. Series 5 footnote: August 2019 test. Neither page publishes Low Power Mode hours or a 15-minute fast-charge figure. Do not invent them.
Price
Both SKUs are discontinued. Apple Support is the spec source. This page does not treat classifieds or refurb tickets as facts.
Frequently asked questions
What did Series 5 add over Series 4?
Apple’s 10 September 2019 Newsroom post: Always-On Retina display and a built-in compass (plus international emergency calling in that launch copy). Support 118453 lists Always-On Retina LTPO OLED with Force Touch, S5, 32GB, compass, and fall detection on the accelerometer row. Series 4 Support lists Force Touch without Always-On, S4, 16GB, and no compass row. Same 40/44mm pixel grid on both Support pages.
Is Series 4 Always-On?
No. Support 111984 lists an LTPO OLED Retina display with Force Touch at 1000 nits. Always-On is not on that spec sheet. Always-On is the Series 5 debut.
Do they share a display resolution?
Yes, as printed. Both Support pages list 40mm 324×394 (759 sq mm) and 44mm 368×448 (977 sq mm) at 1000 nits. Series 5’s change is Always-On (and Force Touch remains listed on 118453), not a new pixel grid.
Does Series 4 or Series 5 get watchOS 27?
Apple’s Series 12 Newsroom (9 September 2026) says watchOS 27 will be available for Apple Watch Series 9 or later, Apple Watch SE 3, and Apple Watch Ultra 2 or later, and requires iPhone 11 or later or iPhone SE (2nd generation or later) with iOS 27. Series 4 and Series 5 are not on that list. This page quotes Apple.
Do both have ECG?
Yes. Series 4 introduced the electrical heart sensor and ECG app (12 September 2018 Newsroom). Series 5 Support lists the electrical heart sensor. Apple’s later ECG footnote: Series 4 and later, excluding SE models. Region and age limits apply.