The aim here is to bring you a full comparison of all major 3 rings (Oura, Circular, Ultrahuman)

We are big fans of minimalist wearable electronics - smart rings. To be more precise, we are 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.

Currently, these three meets our requirements:

  • Oura 3
  • Circular Ring
  • Ultrahuman Ring R1

Sizing kit

The sizing kit is a well-established piece of equipment for proper ring choosing, which you will receive in advance.

There won't be anything especially interesting about the sizing kit, it is plastic rings of different sizes. Manufacturers also share data for possible home printing on a 3D printer. 

Sizing kits: Oura vs Circular vs Ultrahuman
Sizing kits: Oura vs Circular vs Ultrahuman

Ultrahuman will have 7 sizes, 6-12, which is one less than the current Oura and Circular (the latter plan of the Circular team is to add two more over time).


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 (for Ultrahuman this feature will be released later), and green for daytime HR.

HW comparison
HW comparison

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, Ultrahuman charger is very similar to Oura, 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, we like the Oura charger more.
  2. Design customization - with Oura and Ultrahuman, you pick once the ring and you're done. There are Gold, Silver, Black and Matte options (I'm not considering the Gucci thing). For Ultrahuman, there are Cyber Grey, Bionic Gold, Aster Black, Space Silver. 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 and Ultrahuman are a pure data collectors without any user input except the app, Circular has a button. It can be used to turn on/off, deactivate notifications - such as a smart alarm clock, or control the mobile music player. We 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 and Ultrahuman 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 disablement of Bluetooth. This functionality can be popular with a lot of biohackers :)
  6. Material - Oura is made of titanium which can be in experience by many users scratched very easily. As Circular is mainly made of plastic, the durability is not very good. Very interesting here is Ultrahuman Ring with the bonus of a scratch-resistant Tungsten carbide coating. This should make the ring very durable with the elimination of possible scratches. They mention that you don't have to worry about using it in the gym, for example, which I can't quite with Oura and I rather take it off in the gym.
Oura charger vs. Circular charger vs. Ultrahuman charger
Oura charger vs. Circular charger vs. Ultrahuman charger
Oura variants vs. Circular Outer shells vs. Ultrahuman variants
Oura variants vs. Circular Outer shells vs. Ultrahuman variants


All three rings have an app for iOS and Android. 

Apps all of them
Apps all of them


With sleep metrics, it's a bit difficult to identify what they actually tell us, as manufacturers use different terminology and Ultrahuman is generally not very open to sharing much info.

Sleep metrics comparison
Sleep metrics comparison

The big unknown with Circular an Ultrahuman is, of course, the quality of the data. In principle, I think that for sleep data - especially the calculation of sleep phase estimates, Circular&Ultrahuman 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
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. Very interesting is also live measurements available for Circular users.

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

Ultrahuman is currently priced somewhere between Oura and Circular with a price tag of 299 EUR, but since it is still a preorder, it is possible that the price will go up. No form of subscription is planned for access to the ring data. If I understand their model, for CGM data, of course, there is.


It looks like the smart rings are coming and it will be very interesting to see which ones catch on and which ones fall into oblivion.

Oura Ring 3 is still number  1 in this segment, no doubt about it.

Circular Ring, on the other hand, bring some fresh ideas including button and vibration and some nice extra features (as are for example live measurements and smart ring).

Ultrahuman Ring R1 is a materially more durable copy of the Oura with less functionality (e.g. SP02 is missing, but should be released later). If we see it within the Ultrahuman ecosystem with the M1, i.e. CGM sensor, it may be a new dimension of data, but that has its limits especially given the need to replace CGM sensors (which of course makes the whole thing more expensive).A much more interesting path in this vein is being led by Movano, which plans to implement non-invasive CGM (and also blood pressure measurement) directly within the ring sensors, which would take smart rings to the next level.

What is your choice?