Circular Ring Review

Over the past three months of intensively testing a range of smart rings, I’ve been impressed to see beautifully crafted pieces of discrete smart tech. A far cry from the bulky, first-generation Oura Ring I tested in 2017. I have some thoughts to share in this review of the Circular Ring, which at €204 is one of the more credible, cheaper-priced alternatives. I’ll also share which rings are suitable for which kinds of people and when to opt for a ring over a smartwatch.

Buy: From €204

Practicality

The most significant advantage of smart rings is that you can wear and forget them for extended periods. They typically have a 4 to 7-day battery life, and you can live normally without realising you’re wearing a ring – working out, sleeping, walking, driving, dining out – it’s all good. Gone are the bulky first-generation rings; the current crop is typically a few millimetres thick, and each weighs only a few grams. To all intents, they are slightly larger than a typical banded ring, yet they pack in a battery, lots of sensors and Bluetooth.

Key Stats – Circular Ring

The key specs vary slightly depending on the ring size you order:

• Dimensions: 8.8 mm wide, 2.2 mm thick
• Weight: 2 grams.
• Battery Life: 3-5 days, depending on mode and usage. Fast recharge takes 45 minutes.

Smart rings offer a genuine alternative to smartwatches. OK, you don’t get a screen, but you get the same suite of sensors that pass back the same information to the ubiquitous smartphone app and Apple/Google Health. Regardless of the ring brand, you get similar, valuable insights into your health, sleep, and energy levels. Whilst Samsung Ring only works on a Samsung phone, Circular is suitable for any modern smartphone and packs in these capabilities

• 24/7 heart rate tracking
• Blood oxygenation (SpO2) monitoring
• Heart rate variability (HRV) tracking
• Sleep and activity tracking – waterproof for swimming
• Temperature variation trends
• Guided breathing exercises
• Smart alarms and notifications
• Haptic feedback with a vibration motor

Getting Used to a Smart Ring

If you’re used to wearing a ring, nothing surprises you other than the inside of this ring, which you don’t usually see—rotating the ring to have the sensors on the fleshy part of your finger works best.

Size is important. Each of your ten fingers/thumbs is differently sized, so you’ll need to pick a finger for your smart ring and stick to it. The €5 cost of the sizing kit is refunded against the purchase, and you’ll want a snug fit where the ring will not fall off but can still rotate. The index finger is often said to be the ideal finger to wear a smart ring, but many scientists seem to think it doesn’t make much difference.

Are smart rings accurate? Is Circular Ring More or Less Accurate?

Smart rings have the potential to be reasonably accurate in most scenarios, except for intense sporting activities. Why? The finger has excellent blood flow, but sensing it when there is a lot of movement during sports is hard.

Here are my thoughts on Circular’s accuracy for each of its sensors:

• 24/7 heart rate tracking – seems plausible, and spot readings appear broadly correct.
• Steps are plausible, in the right ballpark, and correctly skew much higher on days when I run. Unlike other rings, it doesn’t count cycling as steps!
• Blood oxygenation (SpO2) monitoring – averages 98%, lower than I would expect
• Heart rate variability (HRV) tracking – values are similar to all my other sources (Ultrahuman was much higher). It did not correlate well with waking HRV with a Polar H10.
• Sleep tracking – great at getting the asleep and awake times correct
• Temperature variation trends – values seem to trend sensibly.

Here is one example of high-intensity exercise: I ran intervals with an Apple Watch and a Wahoo chest strap. Superficially, the ring recognises intervals but wildly understates the actual HR effort and does not record each interval. It’s wrong for intense sport, like all rings.

Overall App & Ring Experience

I used the original Ciruclar app/ring back in 2022, and it was not great. As of August 2024, the experience is far more credible and eminently usable.

I like the ring’s aesthetics; although the charging pins catch the skin slightly, the tiny, etched logo on the outer surface surprised me.

The app seems to try too hard to be young and fresh when all I want is the insightful presentation of information. Overall, the Circular Ring app is clunky in places and not as well-polished as the Oura app. Sometimes, I’ve lost small amounts of data either because of having to re-pair the ring or it just inexplicably not recording HRV data overnight.

Circular Ring – Personalisation & Some Points of Difference

Circular has a licencing agreement with Oura to use the latter’s patented technologies. While this represents increased costs for Circular, it validates its approach. Circular must be doing something right to share similar tech with the market leader.

Haptics are also on offer in one of the ring models. These vibrations are helpful as a simple timer, a guide for breathing or an intelligent alarm clock based on your body.

Kira is Circular’s AI assistant, currently available as a beta feature, designed to bring personalised insights from your sleep and energy data after a 2-week learning period. Circular is off to a good start here but all the competition will soon have similar AI offerings up and running. Indeed, Oura recently announced an AI Camera tool for calorie-logging meals from a single photo.

Circular Ring – Choosing The right Ring

Remember that some team sports might not allow you to wear a ring, and gym sports might be uncomfortable when you grip a bar.

You’ll buy a smart ring as a daily tracker and perhaps as a superior and more comfortable sleep tracker than a smartwatch. If you avoid high-intensity exercise but like to be active, a smart ring is a great choice.

• Oura Ring – you want the best ring and app. You don’t mind paying a premium for the ring and paying a subscription.
• Ultrahuman Ring Air – On par with Oura and benefits from not needing a subscription. Its app isn’t quite as good. That said, Ultrahuman is an attractive long-term bet for biohackers interested in capturing other data types with the company’s other products.
• Samsung Ring – you have a Samsung Galaxy phone, maybe a Samsung Watch as well, and want a one-vendor solution.
• RingConn Gen 2 – Similar headline features as Circular with a lower headline price, thinner format and longer battery life. I’ve not tested it; it’s a new kid on the block, currently only on Kickstarter.
• Circular Ring Slim Light – You’re unsure about committing to a subscription, and cost is important. Circular would make it even easier for you if they lowered the price by €50 to about €160

Smart Ring Competitor Pricing

• RingConn Gen 2 (Kickstart intro price) – $209
• Oura Ring – $299 plus subscription
• Ultrahuman Ring Air – $350
• Amazfit Helio ring – $299 $201
• Samsung Ring – $399 (can’t be repaired, and it has a 1-2 year life at best!)
• Circular Ring €204 without haptics (vibrations), €294 with haptics (vibrations)

As of August 2024, I would only consider these rings. They are all fine as simple sleep trackers for those who don’t want to wear a watch at night. Circular has a good feature-to-price ratio BUT is beaten by RingConn’s Kickstarter discount (which will go away in September 2024, and you are buying an unproven ring). Ultrahuman and Oura are on par with each other. Oura has the best piece of hardware and app but is the most expensive. Ultrahuman’s ecosystem includes other products covering blood and indoor air health. Only consider Samsung if you have a Samsung Galaxy phone.

Circular Ring Review – Take Out

As a smart ring, Circular does not match the heady heights of the market leader, Oura. Sure, it’s priced considerably lower. But so are some of its competitors.

Circular either needs to lower the price or double down and improve the app’s look & feel to make it a more serious-minded product. All of the techiness needs to be hidden and work seamlessly. I don’t want to know how the data synchronisation has progressed with the server, and I don’t want to choose a performance mode. I also don’t want to see popups and awards every day.

The accuracy seems broadly OK. Sports accuracy will be wrong for any smart ring, but all smart ring companies will have to convince YOU that it isn’t essential!

If you want to support the company or try a new tech for the first time, go for it. You’ll learn a lot about yourself with a relatively well-implemented and highly convenient form factor – it’s a fantastic product if this is your first activity and sleep tracker.

• Circular €204 without haptics (vibrations)
• Circular €294 with haptics (vibrations)