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 right for which kinds of people and when to opt for a ring over a smartwatch.

Buy: From €204

Practicality

The biggest 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 your life normally and not realise 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 do get the same suite of sensors that pass back pretty much the same information to the ubiquitous smartphone app and Apple/Google Health. You get similar, valuable insights into your health, sleep, and energy levels regardless of the brand of ring. Whilst Samsung Ring only works on a Samsung phone, Circular is good 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 will surprise you other than the inside of this ring, which of course you don’t normally see. It works best if you rotate the ring to have the sensors on the fleshy part of your finger.

Size is important. Each of your 10 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 much of the science seems 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 – 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). 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 where I ran intervals with an Apple Watch and a Wahoo chest strap. Superficially the ring recognises intervals but wildly understates the true 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 and the tiny, etched logo on the outer surface might come as a surprise.

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. Whilst this represents increased costs for Circular, it validates the company’s 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 useful 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 interesting long-term bet for biohackers interested in capturing other types of data 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
• Samsung Ring – $399 (can’t be repaired, 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 of you 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 the best app but it’s the most expensive. Ultrahuman’s ecosystem includes other products that cover blood health 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 further lower the price or double down and improve the app’s look & feel perhaps to make it a more serious-minded product. All of the techniness needs to be hidden and work seemlessly. I don’t want to know how the data synchronisation has progressed with the server and I don’t want to have to choose a performance mode nor do I 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 all have a job of convincing YOU that isn’t important!

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

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