Samsung Galaxy Watch 4 40mm Review: Is the Renewed Version Worth It?

Quick Verdict

The Samsung Galaxy Watch 4 40mm renewed is a capable wellness companion at a price that makes the otherwise pricey Samsung ecosystem accessible. It earns a 4.2 out of 5 for fitness-focused shoppers who want ECG, GPS, and sleep data without paying full retail. The renewed unit we tested held up well, though you'll want to budget separately for a charger if your box doesn't include one.

What Is the Samsung Galaxy Watch 4?

The Samsung Galaxy Watch 4 is a 40mm aluminum smartwatch that runs Wear OS 3, developed jointly by Samsung and Google. It sits at the intersection of fitness tracker and full smartwatch — designed for people who want granular health data but don't want to carry a separate HR monitor on every run. The renewed version we're reviewing here has been inspected, cleaned, and certified by Samsung or an authorized partner to function identically to a new unit, typically at a 15-30% discount.

In practice, that means you get everything the factory-fresh version offers: heart rate monitoring, ECG, blood oxygen, sleep stage analysis, GPS tracking, and access to the broader Google Play Store for apps. The trade-off is purely cosmetic — the aluminum casing on our unit had a couple of hairline marks on the bezel that wouldn't show up unless you angled it under bright light.

Key Features

• ECG sensor for atrial fibrillation detection and rhythm analysis
• Optical heart rate monitor with continuous tracking mode
• Built-in dual-band GPS for route mapping on outdoor activities
• 40mm Super AMOLED display at 360×360 resolution
• Sleep tracking with REM, deep, light, and awake stage breakdown
• Blood oxygen (SpO2) monitoring during sleep and on-demand
• Fall detection with automatic emergency alert capability
• Wear OS 3 access to Google Maps, Play Store, and third-party fitness apps

Hands-On Review

I unboxed the renewed Galaxy Watch 4 on a Tuesday morning — the packaging was clean, no scent of cigarette or warehouse dust, which honestly surprised me given it's not fresh-from-factory. The aluminum case in silver has a matte finish that hides minor scratches well. Strapping it on for the first time, the 40mm size sat almost flush against my wrist; I've worn chunkier fitness bands that felt more obtrusive.

Day one was a mixed bag. Setting up Samsung Health and pairing over Bluetooth took about 12 minutes, mostly because the watch firmware needed a post-unboxing update. Once updated, the AMOLED screen was immediately impressive — notifications were crisp, watch faces looked rich, and the rotating bezel (a Samsung signature) navigated menus with a satisfying tactile click. Yes, it's a virtual bezel, but the haptic feedback makes it feel physical.

By day three, I started taking the health tracking seriously. I wore it through two morning runs — one on the treadmill at the gym, one outdoors with GPS enabled. The outdoor run was where the Watch 4 earned its keep. GPS lock was steady within 30 seconds, and reviewing the route afterward in Samsung Health showed a clean, accurate track. My heart rate zones during that run matched what I'd expect from effort level, give or take a few BPM — consistent with other optical HR monitors in this price range.

Sleep tracking is where things got interesting. I've been skeptical of consumer sleep data since most trackers give you a number that feels arbitrary. The Galaxy Watch 4 does four-stage tracking, which is more granular than what I'd been using before. After five nights, the app surfaced a pattern I hadn't noticed: my deep sleep was noticeably shorter on evenings when I worked out after 7 PM. I can't confirm that's causation, but the correlation was consistent enough that I changed my schedule. Will I keep using it? Probably — but with a caveat. The 36-hour battery life meant I had to charge it mid-day every other day, and forgetting that once meant going to bed with a dead watch and no sleep data.

The ECG feature works as described. I tested it a handful of times across the three weeks — results came back as sinus rhythm each time, which matches what I'd expect at 34 years old with no known heart conditions. What surprised me was the blood oxygen readings during a mild cold one weekend — the app flagged a dip to 91% overnight, which normalised by morning but prompted me to rest rather than push a run. That's the kind of signal that makes the data feel useful rather than just interesting.

Who Should Buy It?

Fitness-focused Android users who want one device for workouts and daily health monitoring. The built-in GPS, heart rate zones, and workout recognition (it auto-detects running, cycling, swimming, and elliptical work) make this a genuine training companion, not just a notifications watch.

Anyone transitioning from a basic fitness band to a full smartwatch. The Galaxy Watch 4 bridges that gap — it does everything a band does but adds apps, maps, and a proper display. The 40mm size keeps it from feeling overwhelming for people who find 44mm+ watches too bulky.

People interested in sleep quality and recovery data. If you've been meaning to understand your sleep patterns beyond "I slept OK," the Watch 4's stage tracking and SpO2 data give you enough to act on — especially if you pair it with Samsung Health's weekly trends view.

Skip this if you want seamless iPhone integration — the full experience requires Android. Also skip it if you need multi-day battery life without compromise; the Watch 4 demands a charging habit, and two days is the absolute ceiling under moderate use.

Alternatives Worth Considering

Fitbit Sense 2 — if ECG and stress management are your priorities and you prefer Fitbit's ecosystem, the Sense 2 offers comparable health features with a longer battery life (around three days). The trade-off is a smaller app library compared to Wear OS 3.

Garmin Forerunner 55 — for runners who want GPS-first tracking with exceptional battery life (up to a week in basic mode), Garmin remains the gold standard. The trade-off is a monochrome display and no smartwatch app ecosystem.

Samsung Galaxy Watch 5 40mm — the newer model adds a stronger glass, slightly better battery, and a body composition sensor. If the price gap is small, it's worth the upgrade. If you're on a budget, the Watch 4 renewed delivers 90% of the same health and fitness experience for noticeably less.

FAQ

Final Verdict

The Samsung Galaxy Watch 4 40mm renewed model is a smart buy for anyone who wants Samsung's health-tracking depth — ECG, GPS, sleep staging, SpO2 — without paying full price for a brand-new watch. Our three-week test showed consistent performance, a comfortable fit for all-day wear, and data quality that stacks up well against competitors at this price point. The battery is the honest limitation: you'll need to build a charging habit around it. If that works with your routine, the Watch 4 renewed is one of the best value Wear OS health watches you can pick up right now.