Oura 3 vs Circular Ring — paper-based comparison

I am a big fan of minimalist wearable electronics — smart rings. To be more precise, I’m mainly interested in rings that primarily measure…

Oura 3 vs Circular Ring — paper-based comparison

UPDATE — 01/2023 — I published a full review of Circular ring — here.

I am a big fan of minimalist wearable electronics — smart rings. To be more precise, I’m mainly interested in rings that primarily measure body metrics and sleep (one could say fitness and sleep trackers), not rings designed primarily for payment, etc.

I have been loyal to the Oura brand for over three years, firstly in the second generation and currently in the third-gen.

Recently, one new ring has appeared that I don’t think blindly copies Oura (although maybe Oura thinks otherwise — https://www.engadget.com/oura-circular-smart-ring-lawsuit-133032301.html), but brings something extra. It is a Circular ring.

I was also slightly disappointed by the approach of Oura company, which came with GEN3, but which was in fact more like version 2.2/7 (if I calculate with the 7 new features they announced here), and the releases of new functionalities is delayed. However they probably have enough energy and capacity for innovation, because they came up with “fancy nonsense for snobs”, a collaboration with Gucci :) A lot of other users were also not happy with the introduction of a premium subscription app from Gen3.

So I started to look around more for Oura’s competitors:


So I ordered the Circular ring and in order to make the waiting short, I prepared a little comparison which I will share in this article.

Sizing kit

There won’t be anything especially interesting about the sizing kit, it is plastic rings of different sizes. Both manufacturers also share data for possible home printing on a 3D printer. For some reason, I did not receive sizes 14 and 15 with Circular.

It’s probably not a coincidence that I chose the same size for Circular as I currently have for Oura. But in any case, I am not suggesting a similar shortcut.

But let’s take a look at the specifications of the rings themselves.


Within the paper-based HW specifications we find a lot in common, a trio of sensors, infrared for night HR (Heart Rate), red for Sp02, and green for daytime HR.

HW Comparision

Let’s focus in particular on the differences:

  1. The charger — the Oura 3 has a horizontal charging dock with a USB-C cable that can be plugged in basically anywhere, while the Circular comes with a sort of weird key “flash drive” charger also with USB-C (male) where the ring is de facto hanging. Personally, I like the Oura charger more.
  2. Design customization — with Oura, you pick once and you’re done. There are gold, silver, black and matte options (I’m not considering the Gucci thing). Here you have only 1 way of changing the design — purchase a new ring. Circular brings a rather interesting concept of interchangeable Outer shells that snap onto the body of the ring. The color options are gold, black, silver, and pink. Personally, I probably won’t take this opportunity, but it is an interesting move for some users.
  3. Push button! — while Oura is a pure data collector without any user input except the app, Circular will have a button. The question is what its use will be, at the very least it is expected to be used to turn on/off, deactivate notifications — such as a smart alarm clock, or to control the mobile music player. I can also imagine the possibility of rejecting a call, as it is offered by, for example, a smartwatch connected to the phone.
  4. Circular vibration motor — the second of the two main HW advantages of the Circular ring. It will allow discrete notifications — e.g. a smart alarm that should wake you up in a light sleep phase, more in the SW section.
  5. EMF — both rings work on the basis of Bluetooth. But while with the Oura you have to activate Airplane mode manually (and its deactivation is only possible in connection to the charger), the Circular promises automatic transition to sleep mode and automatic disable of Bluetooth. This functionality can be popular with a lot of biohackers :)
Oura charger vs. Circular charger
Oura variants and Circular Outer shells


Both rings have an app for iOS and Android. We can’t compare them yet, so let’s take a look at the parameters of what they display, i.e. what parameters they can interpret within the UI and what functionalities they have, first in the sleep category.


With sleep metrics, it’s a little difficult to identify what they actually tell us, as the two manufacturers use slightly different terminology. But I tried to consolidate it (Oura terminology / Circular terminology), see the comparison table below.

Sleep features comparison

The big unknown with Circular is, of course, the quality of the data. In principle, I think that for sleep data — especially the calculation of sleep phase estimates, Circular will take a long time to catch up with Oura. Oura, thanks to its years of experience, has a huge dataset on which it can tune the algorithm (and hopefully does — and I look forward to the promised 84% success rate in sleep phase determination).

The Circular, on the other hand, comes with a nice feature in the form of a smart alarm clock and an automatic Sleep mode in the sense of eliminating Bluetooth. This basically means that the Circular has to evaluate the sleep phase in real-time, whereas with the Oura, this only happens when syncing in the app.

Daily and Activity tracking

Even in this category, we can find a lot in common, so I will focus more on the differences.

Daily&Activity features comparison

According to the available sources, it seems that Circular should be able to notify (probably by vibrating the integrated motor) when certain limits for HR and Sp02 are exceeded. Circular is also going to calculate the V02max value as well, unlike Oura.

Oura on the other hand has a big draw in the form of a wide range of meditation/breathing/sleep exercises (but only in the premium version).

Let’s talk money and other features

A major difference can be found in the current approach regarding subscriptions, Circular announces that no subscription model is planned, while with Oura you pay EUR 5.99 per month after the first six months.

$$ and high-level features

Here I will also mention my favorite Oura Cloud, which provides (besides API) a perfect dashboard for various analyses, correlation searches, etc. Circular is not known to be planning anything similar.


I find it very beneficial that there is a hopefully (and finally) proper Oura competition coming up that brings something extra. But while Oura is a proven brand that has already released the third generation of its smart ring, the Circular is yet to pass the test.

At the time of writing these lines, no mortals have seen the Circular ring yet and shipments are delayed, though they are reportedly already shipping:


I am very much looking forward to comparing the data from the Oura and Circular ring, especially validating the sleep data through the Dreem2 EEG headband.

If you’re considering getting one or the other ring, try the following links (which I can benefit from a bit as well):