Circular Slim Smart Ring Review – One Ring Closer


Smart rings aren’t new to the tech world. There have been smart rings around the scene since early 2013 although their use has been primarily just for NFC purposes. There are a lot of reasons why people may not have heard of or considered getting a smart ring. That’s because typically rings with this technology are still very chunky. Monitors that can do the things you would ideally like it to; like tracking your steps, and checking your temperature need to get to a size where they could fit in something as small as a ring! That innovation takes time. It’s also one of the reasons why you haven’t seen major players like Samsung or Apple join the race for the smart ring market yet.

The landscape is about to change though. Rumours abound of the Samsung Smart Ring being released in 2024. So there has never been a better time than now to get a state of play as to what’s possible in the smart ring space.

So when I approached Circular to see about their latest smart ring – the Circular Slim I was excited to put it through its paces. I had a very challenging set of circumstances to put it through which is an international move.

Calibration and Kira

There is nothing quite so stressful in someone’s life as to try and organise an international move. So there was nothing I could think of that would put it through its paces better. There is a lot to consider when you’re moving to a new country and there is lots to sort out. Between packing, bills, paperwork and everything else that comes with a move. So tracking my sleep, stress and other metrics was going to be very important. After all, stress can make you additionally sick and that was not time I was willing to lose.

Circular has a 14-day calibration period where you will wear it in performance mode for it to get a better sense of where your baseline is. For you to not subliminally mess with these figures, nothing is displayed in terms of your key metrics or analytics until the calibration is over. This was fine for me, given I was busy and not interested in micromanaging my stats.  But for those who would have liked to dive in from the jump – it may be a little frustrating.

Kira is Circular Smart Ring’s AI which will give you daily feedback as to how you slept the night before or other things that you may need to know. She is limited in her functionality, so don’t go into it thinking it is a ChatGPT-style AI that can be the be-all and end-all. That’s not her role, her role is to be able to track back on the information she does have and be able to make suggestions based on your specific metrics. The more consistently you wear the ring, the more data Kira has to report back. So it is very much a process. The more you use it, the better it will get.

Teething Issues

Connectivity & Syncing

There is no such thing as being a tech reviewer and not stumbling upon some issues. For me, my issues lay in its initial setup and connectivity. I’m still not sure what the overall issue was for the first few days. Connectivity was an absolute non-runner. This doesn’t seem to be an uncommon issue when looking into it, as some of the connectivity issues do take time. It did get so bad that I was concerned that I may have gotten a defective unit. In saying that, magically, many attempts later it all connected just fine. I’m happy to report that I had no further issues with connectivity after that. But it was very strange nonetheless. You would expect there to be a push for some software or firmware updates to be the issue with this, but no. There were no such updates around the initial time of setting up that would have fixed the issue. So instead of a better explanation, I think we’ll just put it down to being some  Ciruclar magic.

There are also some minor issues when it comes to tracking. There is no option for the ring data to be edited. So if it tracks that I have had a nap and I haven’t – there isn’t a way of editing this out of your data for the day. I’ve also had some minor issues around it syncing data if you don’t check in daily with it. Some of my sleep data or steps from the day before would magically go missing but reappear after a resync a few days later. Having the ability to edit these things yourself would go a long way in helping your data to become even more optimal.

Battery Life

Battery life on the device should be kept with a grain of salt. The advertisements say that the Circular Slim Smart Ring should be able to have about 5 days of use before a charge. The reality on the ground is more like 3 days. It’s important to keep in mind that I have kept the ring in performance mode all the time. I’ve never really understood buying something and then not using it at max all of the time. However, your mileage may vary if you choose to set it to a more battery-sipping setting.

Where the magic happens

Where the true magic lies in Circular Smart Rings is in Kira and its productive capabilities. As I’ve documented frequently for Phandroid, I’m one of the chronically ill members of staff and having any heads up about being sick is hugely valuable for me.

For the sake of my privacy, I’m going to be cutting around some of the screenshots but I want to talk you through a series of instances that Circular Smart Ring was able to capture and be able to inform me I was getting sick before I was fully sick.

Firstly, it informed me that there had been a small spike in my resting heart rate and then a big leap in my temperature overnight. Due to all of this when checking my overall stress score. I had an “Overwhelmed” score on my stress levels.

This prompted Kira to chat with me when I had checked in to be like “Hey, your vitals are all elevated as well as your stress scores. This is all a pretty different deviation to normal and you need to try and prevent yourself from getting further run down.” Now, the abnormal stress levels would be normal given moving and trying to organise everything else.

The temperatures and elevated heart rate were abnormal though. Keep in mind, I was still wearing the ring while moving heavy boxes and all the normal activities. So it wasn’t registering those times of extra stress or additional temperatures as irregular. It was calculating them as normal. However, it was smart enough to work out that there were stress and temperature spikes outside the range of activity that were abnormal and an indicator of illness.

I had an idle cough and some phlegm that I was able to get checked out. Sure enough, I was on the way to having an asthma-related respitory infection. So, it saved me from an extended period of being on antibiotics and was able to get away with just preventative medicine and some steroids instead. It allowed me to remain on my feet and keep going as I normally was during a very stressful time.


Impressive AI

Kira and Circular’s ability to be able to do this is very impressive. It is truly where the magic of this ring happens. Being able to inform people of potential issues and then having people able to act on that information could be hugely beneficial to people long term. This can only come from being able to have access to your data over a set course of time so that it can track these variations should they occur. There is nothing short of saying that this technology is cool and has a lot of potential.

We tend as humans to want all-encompassing solutions. I think when you look at Circular and their smart rings you need to keep tempering your expectations. Kira and Circular are very good at doing this very specific set of things, but expecting it to do more than what it will lead you to be disappointed.

In fact, if you look at its current subset of things. There could be an argument to be made that it’s quite limited in its skillset. But what it does – it does very well.

Rounding up

The Circular Slim Smart ring is an easy recommendation for someone who is looking for a casual tracking device to get important metrics.  If you’re looking for something more in-depth that can track your runs or workouts – then you’re still better off staying with your smartwatch for the time being.

You can check out the Circular Slim Smart Ring for E264 at

Specious Coda-Bishop
Staff Writer @phandroid | Top 5 Kingdom Hearts 3 Speedrunner | Twitch Affiliate | Xbox Ambassador

I Spent 30 Days using a Compassionate AI

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