By Dan Bracaglia,Dan Bracagliase

Copyright tomsguide

While brands like Oura and Samsung dominate the best smart ring space in 2025, smaller startups, including Circular, RingConn, and Amazfit, offer appealing alternatives that don’t require a subscription (unlike Oura) and play nicely with both Android and iOS devices (unlike Samsung).

Having already reviewed the Amazfit Helio Ring and the latest RingConn Gen 2 Air, I was curious to see how Circular’s newest release compares. Having first checked out the Circular Ring 2 at CES 2025 in January, I finally got a review unit on my finger in September.

After three weeks of testing, I’ve found a lot to like about the Circular Ring 2. It’s packed with lots of wellness tools you won’t find on other smart rings, like ECG readings, FDA-cleared AFib detection, and blood oxygen saturation readings (SpO2). Battery life is also impressive, easily lasting a week or more per charge.

That said, a somewhat buggy app with missing features, data transfer issues, a lack of fitness tracking tools, and a steep starting cost of $379 — that’s more than the Oura Ring 4, aka, the best overall smart ring in 2025 — all hold the Circular Ring 2 back from its full potential. Read on to find out why.

Circular Ring 2 review: Specs compared

Circular Ring 2 review: Price and availability

The Circular Ring 2 starts at $379 for the matte black option and increases to $449 for silver and $549 for the gold or rose gold option. This puts the Circular Ring 2 on the higher end of the smart ring cost spectrum.

By comparison, the Amazfit Helio Ring starts at just $199, and the RingConn Gen 2 is $299. Neither of those devices requires a subscription, nor does the Circular Ring 2. The Oura Ring 4, on the other finger, is $5.99 a month.

That said, Circular has plans to roll out a premium subscription model at some point, where advanced features like blood glucose tracking and blood pressure monitoring will reportedly eventually live. No word yet on pricing or when either of those will become available.

The Circular Ring 2 is available now through Circular directly.

Circular Ring 2 review: Digital sizing process

The Circular Ring 2 comes in a fairly large range of sizes from six to 14. Better yet, unlike most other smart ring brands, you don’t need to first shell out $10 for a ‘digital sizing kit’ full of plastic dummy rings.

Smart ring sizing tends to vary from standard ring sizing, and a proper fit is essential for accurate holistic tracking. While Circular does offer an old-school physical sizing kit for $5 for those who really want one, the brand instead recommends that user figure out their sizing using a feature in the Circular app.

Not only is this digital sizing process far less wasteful than the dummy rings, it’s also incredibly fast and easy to perform.

It requires nothing more than your smartphone camera, your hand, and a credit card (or something that size, like a hotel room key). I tried it on the CES 2025 show floor, and it worked remarkably well. With your hand and credit card in the frame, you simply snap a photo and let the app do some AI churning.

A few moments later, you’re measurements are ready. For each finger, the two closest sizes are provided along with a chart showing where exactly your measurement lies between the two.

For example, my index finger was smack in between a size 11 and 12. However, my ring finger was almost an exact size 11. So, if I were shopping for a Circular Ring, I’d likely opt for the 11 and wear it on my ring finger rather than go with the 12 and risk it being a tad loose on my index. Indeed, I tested a size 11 for this review.

Circular Ring 2 review: Comfort and durability

The Circular Ring 2 is a little bit thicker and heavier than most of its rivals. In my four weeks of testing, the titanium alloy exterior picked up more scratches than other rings I’ve tested, too.

That said, it handled several drops on a hardwood floor and knocks into rigid objects like a champ. Water resistance is 50 meters, which is enough for washing your hands or even brief periods of shallow water swimming. It’s also IP68-rated against dust, grime, and moisture. However, given the recent expanding Galaxy Ring news, I might avoid wearing it in salt water.

Most of the Circular Ring 2’s competition boasts 100 meters of water resistance by comparison.

Unlike the latest Oura Ring 4, but similar to the RingConn Gen 2 and Gen 2 Air, the interior sensors on the Circular Ring 2 protrude out, leaving small indentations in your finger that some users may find uncomfortable.

Wearing the Circular Ring 2 for roughly a month, the design proved tolerable, but it’s far from the comfiest smart ring I’ve encountered (that’d be the Oura Ring 4).

Circular Ring 2 review: Tracking sleep and vitals

The companion Circular app for the Circular Ring 2 offers an enormous buffet of wellness metrics, most on a scale from one to 100 with an accompanying rating from ‘needs improvement’ to ‘optimal/excellent.’

These metrics and ratings, which also include AI-generated tidbits and suggestions to help you maintain or improve your scores, are genuinely insightful and even actionable.

With scores for sleep quality, immune system health, energy levels, stress levels, and overall wellness, the Circular Ring 2’s daily insights left me impressed, that is, until I ran into data sync issues that resulted in missing sleep reports and other gaps in my tracking data.

This is not something that I’ve encountered before when testing a smart ring. As of writing, it appears that you must open the Circular app at least once daily to initiate data transfer from the ring to the app, or you lose that info. Sadly, even when I got in the habit of opening the app daily, I still encountered occasional instances where my sleep data (or other) vanished into the ether.

It took just shy of two weeks of continuous wearing for the device to fully calibrate, which is not uncommon for smart rings. During that stretch, the app occasionally asks questions to get a better understanding of your lifestyle, like ‘When is your ideal bedtime?’ or ‘At what time of day do you feel most mentally focused?’

Once fully calibrated, I found the Circular app’s morning sleep reports (when they were actually generated) to be the most useful aspect of the Circular Ring 2. They contain details on your heart rate, breath rate, body temperature, blood oxygen saturation, sleep cycles, body movement, bedtime and wake-up time consistency, and heart rate variability. That’s a lot of data!

After one particularly crappy night of rest and equally dismal morning report, a message popped up on the app asking if any outside factors were at play for my poor rest, with options ranging from ‘too much caffeine too close to bed’ to ‘too much stress,’ to simply, ‘alcohol’ (don’t worry, you can select as many that apply).

Circular doesn’t advertise any sort of nap detection, which is a shame, because I live for a mid-afternoon snooze. Indeed, none of the ones I took while wearing the device registered as sleep in the app.

The Circular Ring 2 is also among only a small handful of modern smart rings with ECG readings. It’s even FDA-cleared to monitor for irregular heartbeats that could indicate Atrial fibrillation (AFib), a potentially deadly condition.

The ECG reading process is quite simple (in theory). Users place their index finger on the surface of the ring while it’s being worn on the other hand for 45 seconds. Unfortunately, despite numerous attempts, I wasn’t able to get the feature to work. Each time I took a reading, the results said my ECG couldn’t be analyzed. (I’ll keep trying and update this review if my luck changes).

Circular Ring 2 review: Fitness tracking

While I appreciate the Circular Ring 2’s daily energy score and occasional workout recommendations, as a whole, fitness tools are lacking. The smart ring only autodetects simple workouts like walking and running. You can manually start a workout session from the app by selecting your activity of choice from an extensive list, but the actual data generated from the session is minimal.

For example, I manually tracked a recent weight-lifting session — though I don’t recommend pumping iron while wearing a ring of any kind — and was treated to the following datapoints in my post-session report: heart rate, workout time, and calories burned.

For outdoor walks where the ring piggybacks on your smartphone’s GPS data — there’s no onboard GPS — you get slightly more data, including distance covered and average speed.

Circular Ring 2 review: Battery life

The Circular Ring 2 has a battery life rating of eight days in ‘power’ mode and five days in ‘performance’ mode, where frequent data syncs are prioritized in favor of longevity.

I tested the Circular Ring 2 in performance mode, and to my delight, it easily lasted a week or more on a single charge. After the first charge-up, I got nearly eight days of usage.

The clamshell-style charging case that comes with the ring holds three full recharges and connects to power by USB-C. Compared to Oura’s new all-metal charging case, Cricular’s lightweight plastic case feels a bit cheap; I’m not certain it could survive a three-foot drop onto a hard floor.

Speaking of Oura, this is one notable area where the Circular Ring 2 has the Oura Ring 4 beat. While the latest Oura Ring is similarly rated for eight days per charge, it didn’t quite last that long in our testing.

With the case connected to a power source, the Circular Ring 2 can fully recharge in a little over 30 minutes.

Circular Ring 2 review: Verdict

The Circular Ring 2 shows a lot of promise, but as of writing, a buggy app with data sync issues holds it back. After all, with no onboard screen, a smart ring is only as good as its companion app. That’s a shame, because Circular offers more metrics and insights than a lot of the competition, save for Samsung and Oura.

It’s also one of the only smart rings with ECG readings, though I was unable to get the feature to actually work. Fitness tracking tools, unlike holistic ones, are limited.

If you’re tempted by the Circular Ring 2’s blood glucose tracking or blood pressure monitoring, curb your enthusiasm. Neither of these features has debuted yet, and when they do, they’ll be locked behind a paywall of undisclosed amounts.

Still, I look forward to revisiting the Circular Ring 2 when these next-gen features do eventually roll out. Hopefully, by then, some of the kinks will have been worked out on the app stability side.

Until then, my favorite subscription-free Oura Ring alternatives remain the Amazfit Helio Ring, with the Ringconn Gen 2 Air as a close second.