Apple Watches Series 4 40mm

Quick summary

The Apple Watch Series 4 40mm (launched 2018) was a major redesign for Apple’s smartwatch line. The smaller 40mm case is ideal for smaller wrists or anyone who prefers a compact watch face. Buying pre-owned is a smart way to get the Series 4’s signature features—ECG, fall detection and a faster S4 processor—at a lower price than the original retail cost.

Explore the wider selection of Apple smartwatches on Relovie to compare models, prices and conditions: Apple smartwatches.

What makes the Series 4 stand out?

• Larger edge-to-edge display — slimmer bezels give more screen area in the 40mm case. Easier to read notifications and apps.
• ECG (electrocardiogram) — an electrical heart sensor that can record a single-lead ECG and help detect irregular heart rhythms (availability depends on region).
• Fall detection — uses improved accelerometer and gyroscope to detect hard falls and can call for help automatically.
• S4 64-bit dual-core chip — faster app launch and smoother animations compared with earlier models.
• Water resistance to 50 metres — suitable for swimming and daily wear.

Technical highlights

• Launch year: 2018
• Case size: 40 mm (also available in 44 mm)
• Display: LTPO OLED, larger than Series 3 in the same case size
• Health features: ECG, optical heart sensor, fall detection
• Connectivity: GPS and optional cellular (depending on model)
• Battery: typically up to 18 hours of mixed use

Models in the same series and where to look

The Series 4 is part of Apple’s generation-based lineup. Related models you may also find on Relovie include:

• Apple Watch Series 5 — adds always-on display and slightly improved internals (Apple Watch Series 5).
• Apple Watch Series 6 — improved sensor accuracy and faster chip (Apple Watch Series 6).
• Apple Watch SE 40mm — a budget-friendly modern alternative with many core features (Apple Watch SE 40mm).
• Newer Series 7, 8 and 9 models — larger displays and more recent software support (Series 7, Series 8, Series 9).

How the Series 4 compares at a glance

Price guide

There are currently available pre-owned products priced between 115 and 246.

Use filters to narrow by price and condition. As you discover pre-owned options, compare original retail price, condition level and delivery terms on the selling site to judge value.

Things to consider when buying pre-owned

• Battery health and typical battery life. Some sellers list estimated battery capacity; check the listing for details.
• WatchOS support. Older models may not run the latest software features. Review the seller’s listing for the current watchOS version installed.
• Case and screen condition. Scratches and dents affect aesthetics but not necessarily function; condition grades are shown on the listing.
• Cellular models require an eSIM and a compatible mobile plan. Confirm compatibility on the seller’s site.
• Included accessories such as charging cable and original box vary by seller—details are available on the product page you click through to.

Quick buying checklist

• Confirm model size is 40 mm.
• Check whether the listing is GPS only or GPS + Cellular.
• Compare price against original retail price and condition grade.
• Read the seller’s shipping and return terms on the site you click through to.

FAQ

Find and buy Apple Watches Series 4 40mm via Relovie – the largest collection of pre-owned and refurbished electronics online.