Oura’s stylish smart ring worn by celebrities and athletes alike has slimmed down for its fourth iteration, making it easier to put on, more comfortable to wear and last longer between charges.The Guardian’s journalism is independent.We will earn a commission if you buy something through an affiliate link.Learn more.The Ring 4 swaps the clear plastic insides of its predecessor for shiny titanium to look even less like a cutting-edge piece of tech on your finger.

It still weighs practically nothing – 3.3g to 5.2g depending on size – and comes in an expanded choice of 12 sizes and six finishes, including black, silver, gold and rose gold.But this level of sophistication doesn’t come cheap, costing from £349 (€399/$349/A$569) and requiring a £5.99 (€5.

99/$5.99/A$9.99) a month subscription to access anything but basic daily metrics.Inside of the new ring the three small sensor domes under your finger in the Gen 3 have been removed leaving two imperceptible bumps and array of dark windows flush to the surface.That makes it more comfortable to wear and much easier to get it on and off over knuckles.

At 3mm thick the ring is still about twice the depth of a standard wedding band.But Oura says its improvements mean many of its users can go down a size compared with the Gen 3, which will help reduce its impact on adjacent fingers.Upgraded sensors allow the Oura to better adjust to your finger’s shape, skin tone and orientation as the ring spins around it, increasing tracking accuracy and reducing gaps where it couldn’t correctly detect a pulse or other metric.Some of the sensors can also be turned off when not needed, which helps extend battery life to just under six days between charges for the size eight Ring 4, which is about a day longer than the equivalent Gen 3.Oura’s unique selling point is still its comprehensive and effortless sleep tracking as the cornerstone of general health, but it has slowly added more and more features to track daytime health trends for a more holistic view.

In addition to basic steps and calorie activity tracking, the rings can monitor cardiovascular health and automatically track 40 different workouts with heart rate zones.Oura’s comprehensive women’s health, fertility and pregnancy tracking has been expanded, and the ring can be used with the Natural Cycles birth control service.Its exercise tracking is still basic compared with a running or smart watch, but Oura can import workouts from third-party services such as Strava, which helps it to get a better picture of your overall health.Oura has overhauled its app to help manage the multiple metrics its rings now collect.The Today tab is dynamic and shows what is happening now, which is typically your activity, stress, heart rate and a timeline of the various events of your day such as when you woke up, when you ate, exercise and other things you can tag manually.

A row of scores for readiness, sleep, activity, heart rate and stress provides one-tap access to them at the top of the page.The Vitals tab shows all the metrics the ring tracks, which are collected under overarching scores for readiness and sleep, your activity goal, daytime heart rate and stress.Many of the scores have baseline bars, so you can quickly see if things are currently within your normal range.Or you can expand each of them to see the various metrics that contribute to the score, including graphs and charts going back over the last days, weeks or months.The final tab is My Health, which is for long-term trends, such as your resilience to stress and illness, cardiovascular age and capacity, your sleep chronotype and various weekly and monthly reports.

The app also has a couple of AI features, including a meal logging system that recognises what you’ve eaten using your phone’s camera and puts it into your timeline.It works surprisingly well, even for random home-cooked meals, but is geared up for charting eating regularity rather than calorie counting.It also has a new “Oura Advisor” AI chatbot, which looks at your health data and attempts to guide you towards a goal, providing a bit of mentoring or support.It can check in on you during the day via a notification on your phone to ask how you’re feeling, and in my two weeks of testing it was smart enough to understand that the reason my daily activity had decreased was due to recovery from injury.Whether it proves useful over the longer term remains to be seen, but for those needing guidance on how to improve a particular aspect of their health it can at least offer tips and motivation.

Overall the Oura app does a far better job of making its myriad metrics easy to interpret at both the macro and micro scale.It is also full of nice touches, such as changing the colour of the graph to correspond to the level of stress and providing haptic pulses on the phone in time to the recorded heart rate.The Oura Ring 4 is not repairable and the battery is not replaceable.The company does not provide an expected lifespan for the battery, but it should maintain at least 80% of its original capacity after 500 full charge cycles.It does not include any recycled materials and Oura does not publish environmental impact reports or offer trade-in or recycling schemes.

The Oura Ring 4 starts at £349 (€399/$349/A$569) with a range of colours and finishes.The ring comes with one month free membership subscription, which costs £5.99 (€5.99/$5.99/A$9.

99) a month or £69,99/€69,99/$69,99/A$109,99 annually and is essential.

For comparison, the Samsung Galaxy Ring costs £399, the Ultrahuman Ring Air costs £329 and an Apple Watch costs from £219.The Oura Ring 4 is a significant improvement in fit and comfort over predecessors, and doesn’t remotely look like a piece of technology on your finger.Removing the sensor bumps on the inside of the ring has made it much easier to live with, particularly if you can wear a slightly smaller size, because it is still quite thick compared with a regular wedding band or similar.Its accuracy and battery life improvements are welcome.Oura’s best-in-class sleep and general health tracking, as well as its good app and reliable syncing keep it ahead of increasingly fierce competition.

If you want accurate health tracking without wearing technology on your wrist, the Oura is the answer.But the best smart ring on the market does not come cheap costing as much or more than a more capable smartwatch.And it requires a £6-a-month subscription on top for anything other than basic data.Just like previous Ouras, the ring’s biggest problem is that it cannot be repaired and the battery cannot be replaced, ultimately making it disposable and losing it a star.Pros: looks like jewellery not tech, comprehensive sleep and health tracking, great analysis of trends and helpful advice, easy to understand, six-day battery life, 100-metre water resistance, effective alternative for health to a smartwatch.

Cons: expensive, monthly subscription, thick for a ring, running and workout tracking is weak, doesn’t do or track as much as a similarly priced smartwatch, cannot be repaired.