I Put on Two Oura Rings to See If the Finger You Use Really Matters
I have always preferred to wear the Oura ring on my ring finger. The company says that “for optimal performance and accuracy” it’s best worn on your index finger, but any finger will do. And if you ask longtime Oura users, you’ll hear a variety of opinions. Does it matter which finger you use? I realized I had the perfect way to test this: I have two third-generation rings that fit my index and ring fingers. I wore both for almost two weeks to compare their performance and answer the question once and for all.
How I did the experiment
As I explained in my four-year retrospective , I’ve worn quite a few Oura rings over the years. I’m currently using a third generation ring (a slightly older model) that I wear on my ring finger. I also had the third-generation headphones that fit my index finger, so I could wear both devices for a few days before bed and compare their readings.
I actually wore three rings, but I didn’t include one of them in the results because it was redundant. This one was a copy of the one I had on my ring finger, so I wore it on the ring finger of my other hand. It was a nearly dead computer that I replaced when it ran out of battery. It still had enough charge to last me through every night of sleep as long as I charged it the next day. However, the readings were almost the same as on my other ring finger, so for the sake of clarity I have excluded this data from the results table.
For this experiment, I needed to connect each ring to a separate account on a different phone . What I do for you, dear readers. Since all the accounts were running on different (or non-existent) inputs, I avoided any scores that the app calculates based on your personal history. I stuck to metrics like resting heart rate, heart rate variability, and sleep time. The only metric I kept was sleep efficiency because it combines multiple measurements in one night.
My results
I always thought the ring finger readings were just as good as the index finger readings, but now I have the data to back it up. Look at these graphs! The readings are often identical and always close. There was one day where the two readings were different – this is the very last day, with different breathing rates and sleep efficiency. On that day, my second ring on my ring finger (data not shown) matched the ring on my other ring finger, suggesting that the outlier was the index finger.
Overall, the readings between the different fingers are much closer to each other than the different devices in this comparison (I wore Oura, Garmin, Whoop, Apple, and Fitbit devices simultaneously for this experiment).
Any of the three placements I used would be perfect for everyday wear. So why does Oura say that your index finger is the best? I contacted the company for more information.
What Oura says
Oura’s 3rd and 4th generation rings fit any finger, an Oura representative told me via email, as long as the ring fits “tightly and securely” to the base of the finger. So why is the index finger preferred? It turns out that this finger is where most people find it easiest to get a good fit.
In particular: “We suggest avoiding fingers with large knuckles, where the base is significantly narrower, which can affect sensor fit and contact. This is why we typically recommend the index finger. If this is uncomfortable or undesirable, the middle or ring finger are also good alternatives. All three fingers have larger blood vessels, which helps optimize PPG pulse monitoring.” (PPG refers to photoplethysmography, an optical sensor system that reads the pulse on the finger.)
So if your ring finger has a large bony knuckle, you will need a larger ring to fit over the knuckle, and the ring will not be able to fit snugly at the base of your finger. I have no problem getting it to fit securely on my ring finger, but I can see that my thumb has a fairly large knuckle and it probably won’t fit well with the ring.
Another sizing issue is that the Oura ring doesn’t come in half sizes, so you may not be able to find the perfect size for your favorite finger. However, 3rd generation rings appear to be about half a size smaller than 4th generation rings with the same number, so experimenting with both sets of sizes can help you find the perfect fit if you’re not picky about which version of the ring you end up with.