How to Size Oura Ring: Determine your Ideal Ring Size

When Oura came out with their newest 3rd generation ring, I knew I had to get my hands on it. Instead of their wrist-worn counterparts, smart ring sizes can’t be winged. So the first order of business was to determine my ring size.

Oura sends a free sizing kit right at your door steps to determine your perfect ring size. The Oura sizing kit comes with 8 plastic rings, sizes running from 6 to 13, mirroring the Oura ring with the sensor bumps. The sizes are slightly different from the standard ring sizes in the US.

Which Finger is Best Suited for Wearing the Oura Ring?

Oura recommends wearing the ring on your index finger for measuring all the metrics accurately, however, as long as it’s a snug fit, it can be worn on any finger.

Your next best bet is your middle or ring fingers. Just be careful to not choose a finger where the base is narrower than the knuckle. That would result in inaccuracy in the measurements.

Since I am someone who goes by the books, you can find me wearing my Oura ring on the index finger of my right hand. It’s pretty comfortable.

Also, Oura also does not provide half sizes, and recommends to size down if you’re in between sizes.

Once you have your sizing kit in hand, follow these tips for choosing the perfect size.

Tips for Choosing the Perfect Oura Ring Size

1. Open your Oura Sizing Kit – Try on the various rings provided in the kit to determine the size. I started with size 6 but eventually decided on an 8 to accommodate for the slight swelling I experience in the morning because of water retention (for $300, they should really be sending reminders for water intake).
2. Choose the Right Finger – For a better fit, choose a size that fits a couple of your fingers so that it’s easy to switch up rather than having one size that seems perfect for one finger. It’ll be convenient on the off chance of you experiencing bloating.
3. Confirm Alignment – To track your metrics accurately, the sensor bumps located on the inside of the ring should be aligned with the base of your finger (palm side).
4. Comfortable Fit – Ensure a comfortable fit on your finger. If you’re in between sizes, size down.
5. Ensure a Snug Fit – Make a fist while wearing the plastic ring. If you see a gap in your finger and the top of the ring, size down.
6. The 24hr Wear Test – While ordering my Oura ring, I had a doubt that it would be a bother in my daily tasks, like an overgrown acrylic manicure (we’ve all been there). The plastic rings are nowhere compared to the real thing, however, the dimensions would give you a pretty good grasp of how they would feel throughout the day. It was because of wearing the plastic ring for a whole day and night that I sized up to a 8 from a 6. 

If you are more patient than I am, try wearing the sizing kit ring for a couple of days before finalizing your size.

Once you’re set on the size you’ll go for, update the size on this page and tap “Confirm Your Size”. After entering your email and tapping on “Submit”, you will receive an email from the Oura team with a link to “My Account” to update your ring size.

While Oura recommends you to “size down”, I would suggest switching fingers with one size throughout the day for a better judgement. You see if you choose a “perfectly snug size” and get bloated because of your cycle or too much salt intake, it could potentially be dangerous to wear a ring that’s too small.

Pro tip: In case your finger swells up in the morning but feels too loose during the day, like mine, I switch up the ring on my other fingers throughout the day. As long as the sensors are placed right and the fit is snug, my metrics aren’t affected.

Determine your Oura Ring Size Without the Sizing Kit

Because I have seen many delays in receiving the sizing kit, I thought of sharing the dimensions here to help out those experiencing these delays. I can’t stress enough how important it is for you to have a snug fit of the ring in order to get accurate measurements.

Although the best way to check would be with the sizing kit they provide to see what it feels like on your fingers and while performing daily tasks, this guide would be your next best option. You’re welcome.

Gen 3 Sizing Info

Ring Thickness – 2.55 mm

Ring Width –  7.9 mm

Size	Ring’s Inner Diameter	Ring’s Bump Diameter
6	16.76 mm	15.21 mm
7	17.60 mm	15.97 mm
8	18.43 mm	16.81 mm
9	19.25 mm	17.63 mm
10	20.02 mm	18.41 mm
11	20.81 mm	19.24 mm
12	21.64 mm	20.05 mm
13	22.48 mm	20.90 mm

Now, I know it’s not as easy as measuring for a pair of pants, but if you’re in a pinch, your girl also wears a geek feather on her cap. Nothing 7th-grade mathematics couldn’t solve. Here’s how to use this size chart:

• Take a rope and wrap it around your index finger
• Cut it to exactly the size of your finger
• Measure the rope, e.g., 6cm
• Divide the number by 3.14 to find the diameter, 6 ÷ 3.14 = 1.91cm or 19.1mm

I would recommend using your calculations to match with the ring’s ‘Bump Diameter’ instead of ‘Inner Diameter’ to get a snug fit. But this would totally be a judgment call.

Beware, this guide will provide you with an idea of what size you should opt for; however, I still recommend getting your hands on the sizing kit for the perfect fit. With this method, you wouldn’t be able to test the sizes for any body fluctuations throughout the day. It also won’t work for you if you have knuckles larger than the base of your finger.

Now that you’ve got the sizing down, what are you waiting for? Go and put a ring on it!

Frequently Asked Questions

Wrap Up

Once you have the sizing kit in hand, choose the right finger and test a few rings to find your perfect match. Position the sensors at the base of the finger, facing the palm. Close your hand to a fist and make sure there are no gaps between the ring and your finger. Wear the plastic ring for at least 24 hrs to check how it blends into your day-to-day activities.