Find Your Perfect Fit: A Guide to Choosing the Right Size for Your Smart Ring

I have many questions about sizing kits and choosing the optimal ring size. I will summarize the information in this article.

Find Your Perfect Fit: A Guide to Choosing the Right Size for Your Smart Ring
Sizing kits

I have many questions about sizing kits and choosing the optimal ring size. I will summarize the information in this article.

I am currently focusing on these smart rings:

  • 💍 Oura ring Gen 3,
  • 💍 Circular Ring,
  • 💍 RingConn Smart Ring,
  • 💍 Ultrahuman Ring R1.

However, it can be said that the sizing process is de facto identical for all of them.


For all the rings listed above, I went through the process of selecting the appropriate size, so I’d like to summarize some key information/experiences:

  • It is possible that you are looking forward to your smart ring, but the optimal size of the ring is absolutely crucial to the overall wearing experience of a smart ring, don’t underestimate it.
  • The recommended finger of the hand is usually the index finger, followed by the middle and ring fingers. Personally, I recommend more of a non-dominant hand, for practical reasons.
  • All the listed smart ring companies send a sizing kit first, which contains 6–14 test plastic rings.
  • The ring's sensors should be placed on the underside of the finger, and it is a good idea to calculate this when wearing.
    The test ring should be worn for at least 24 hours, especially overnight.

Sizing kit

The sizing kit is, as already outlined, the basic equipment for determining the correct size of the final ring. These are usually plastic rings in a paper box.

There are 3 ways to obtain a sizing kit:

  • Standard when ordering — the kit is usually free. Please note, I paid VAT for Ultrahuman in EU.
  • Second hand. Try searching eBay or Facebook. Some sell it for money, which, since it’s included when you order, doesn’t seem quite kosher…
  • Print at home on a 3D printer if you can, see below.

Option #2 and #3 can theoretically speed up the whole process of getting a smart ring a bit, and you can specify the size straight away when ordering, which is normally only entered after receiving the sizing kit.

I recommend getting a sizing kit for a particular ring and not relying on individual brands being compatible with each other. You can find some matches, but rings have different shapes, which is good to take into account.

Size selection process

The process of choosing the right ring is as follows:

  1. Select the finger that will be the “home” of the ring.
  2. Choose the optimal ring size. If you put your hand in a fist, there should be no gap between the top of the ring and your finger.
  3. Wear for a minimum of 24 hours.
  4. Now comes the hard part — assessing whether the size is comfortable/suitable. The ring shouldn’t feel tight, but it shouldn’t be too loose either (this runs the risk of not measuring correctly). A good clue may be that it should not spontaneously rotate (too much) during the day.
  5. Order the final ring.
Hand in left fist = no gap. Gap appears only when thumb is pressed against the ring (right)

Bigger or smaller?

Are you stuck between 2 sizes? I have registered a large number of requests and calls for half sizes. So far, no manufacturer has complied. So it’s necessary to make a decision.

It’s good to remember that the ring has sensors in the body that should be in direct contact with the skin so that they can measure accurately. So the general recommendation would be: smaller. In the same breath, however, I would add that this should not be at the expense of comfort, i.e., the ring should be relatively easy to take off — you can possibly use e.g. soap for a better slip.

The ring doesn’t fit, what to do?

Has your ring arrived and you are not happy with the size?


There should be no need for replacement, hence the emphasis above on the process of selecting the correct size. However, I have mapped out for you how individual manufacturers approach the possible replacement.

  • Oura — size (and colour) exchange is possible within 30 days of delivery.
  • Circular — exchange is possible, shipping is paid by the customer.
  • RingConn- exchange is possible, and shipping is paid by the customer.
  • Ultrahuman — exchange is not possible.

Experimentally — size adjuster

I also came across a rather interesting option — to fill the gap in case of a larger size with a so-called adjuster. This solution may have 2 pitfalls. You must not over glue the sensors and also it is with a question mark whether the ring will fit into the charger with this extender.

I would consider this a very extreme solution, e.g. in cases when you lose weight and therefore your fingers get numb.

Official instructions

I am adding the official sources of instructions, see below.

So, did you choose (right)?