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Oura launched a new version of its iconic ring in fall of 2024, promising better accuracy and a more comfortable design. That’s the fourth-generation Oura ring, which I’ll be calling “gen 4.” It replaces the third-generation, or “gen 3,” ring, which I’ve been wearing ever since my gen 2 gave up its ghost in 2022.
So if you’re wondering whether it’s worth the upgrade—or if you’re buying a ring new and you want to know if the gen 3 will be good enough for your purposes—I’ll walk you through all the important differences, informed by my years of familiarity with the company’s products. For the last few weeks, I’ve been wearing a gen 4 ring (a loaner from the company) alongside my own gen 3. Here’s what I’ve found.
Appearance and comfort
One of the biggest differences—and definitely the most notable—is the shape of the new ring. Instead of having three sensor bumps on the inside, it’s now smooth on the inside, with the sensors pretty much flush with the inside surface of the ring. (And there’s another small upgrade: The interior is now titanium rather than epoxy.)
Besides making for a smoother fit, it means less light leaks out from the watch in the dark. A glowing green finger can distract me (or my kids as I’m putting them to bed) so it’s nice that the gen 4 is a little less glowy.
How much does that smooth fit matter, though? As a longtime Oura user, I truly don’t mind the sensor bumps. They’re not uncomfortable and they’re not going to bother you. I do enjoy the asymmetry of the Heritage shape of gen 3, since you can tell just by feel whether it’s right side up or upside down. But I have to admit the smoother interior is the better design choice.
As for the aesthetics, I’ll let you look at photos to compare. Some Oura users worry about whether the ring will get scratched, and honestly I don’t get it—I see my ring as a utility item, not a piece of luxury jewelry. My old gen 3 has some scuffs on the bottom that don’t bother me in the slightest. So far, the gen 4 is looking brand-new after several weeks, for whatever that’s worth.
By the way, if you’ve been watching forums like the Oura subreddit, you may have seen reports (like this one) of gen 4 rings that popped apart. After some initial uncertainty, Oura announced that this is a known issue, that they found it was happening to fewer than 1 in 1,000 rings, and that they’ve improved their manufacturing and trained their customer service staff to be able to give immediate replacements if your gen 4 ring has this issue.
Sizing
Oura rings come in a variety of sizes, and you need to know which size will fit you before you order your ring. (The charger is also matched to the size of your ring.) The sizing is different between the gen 3 and gen 4 rings—more below on what to expect if you’re upgrading.
So how do you find your size? For the gen 3, which comes in sizes 6 to 13, you’ll need to order a sizing kit, which is a collection of plastic rings that mimic the size and shape of each available gen 3 ring. The sizing kit costs $10, but comes with a $10 credit that you can use toward your ring when you buy it. The company encourages people to share sizing kits, so feel free to borrow your friend’s kit.
Having individual plastic rings means that you can wear the sizer for a day, and even sleep in it, to be sure it fits as you go about your life (fingers commonly swell a bit during the night).
For the gen 4 ring—which, again, fits differently than the gen 3—you have two options. One is to order a sizing kit, as above—but make sure you’re getting the gen 4 kit. It, too, is $10 and comes with a $10 credit for when you buy the real thing. The gen 4 ring comes in a wider range of sizes, 4 through 15 (but still no half sizes).
There is another, quicker option, which is to visit a store that has sizing rings in-store. I found some at my local Best Buy, where the sizing rings were connected by cords to a display on a shelf. This is where I discovered that my usual gen 3 size was not going to work for a gen 4 ring.
The elimination of the sensor bumps means that the new ring fits differently from the old one. You’ll probably need to go down a half size from your gen 3 size to get a gen 4 that fits the same—but Oura rings aren’t made in half sizes. So there isn’t a straightforward size chart that will tell you your ideal gen 4 size. The following are my recommendations, not Oura’s:
If your gen 3 was a snug fit, the same size will feel a bit looser and perhaps fit you better.
If your gen 3 was loose, the same size probably won’t work; consider going down a size.
If your gen 3 fit perfectly, you may want to give up on that finger and choose a different finger that fits one of the gen 4 sizes better.
That last option is what I did. My gen 3 was a size 7 and fit perfectly on my ring finger, but when I tried on the gen 4 sizing rings, the 7 was too loose and the 6 was too tight. I found that an 8 fit my middle finger perfectly, so that’s what I went with.
If the convenience of sizing is a factor in your decision, the gen 4 earns more points here. It’s available in a wider range of sizes, and you have two different options (the at-home kit and the in-store sizers) to find your size. But which ring best fits you, personally, is a question you can only answer by trying them on.
Battery life
Oura says that the gen 4 ring lasts up to eight days on a charge, while the gen 3 lasts up to seven. I put those claims to the test, wearing both rings while I went about my usual activities. I wore the rings to sleep, and I wore them while running, but I took them off to lift weights. (Normally I would charge them while lifting, but for the sake of the battery tests I did not.)
I decided each test was over when the battery dipped down to 20-25%, around the time that Oura sends a notification reminding you to charge your watch before going to sleep. (You need enough charge to get through the night.) Here are my results:
Oura gen 4:5 days, ending at 21%
Oura gen 3: 4 days, ending at 21%
Oura gen 4 with SpO2 off: 6.5 days (25% after 6 days, 19% the following morning)
Oura gen 3 with SpO2 off: 5 days, ending at 22%
In both configurations, the 4th generation ring lasted about a day longer than the gen 3. Neither ring quite measured up to the promised seven to eight days, but they do qualify those numbers with “up to,” and I also didn’t run them down all the way to 0% since I wanted to be sure they wouldn’t die during the night.
The gen 4 ring, without SpO2, was losing about 12.5% of its charge each day—which means it might have been able to squeak out the full eight days if I were willing to risk it.
Factors that affect battery life
When it comes to battery life, it’s important to know that there are a few things that can affect how much use you get from a charge.
Blood oxygen sensing (SpO2) notoriously decreases the battery life of your Oura ring. As you can see above, turning this feature off gives you an extra day of battery. To turn it on or off, tap the menu icon in the top left corner of the app, and tap Blood Oxygen Sensing.
When it’s turned off, you won’t get “average oxygen saturation” or “breathing regularity” in your daily sleep report. These metrics can hint that you may have an issue like sleep apnea, although the company is careful to say that the ring is not a medical device and it can’t diagnose apnea. I would leave this feature turned off unless you have a specific reason to monitor this.
Ring size probably affects battery life. Oura confirmed to me in an email that different ring sizes can have different battery sizes. (My tests were done on a size 8 for the gen 4 and a size 7 for the gen 3.) We might expect larger sizes to have a slightly longer battery life, but I wasn’t able to test this directly.
Age of the ring may also be a factor. I’m a longtime Oura user and I found that my Oura rings’ battery life tends to degrade over time, usually lasting about two years before the ring is down to a one- to two-day battery life. I went through two rings on this timeline, one a gen 2 and the other a gen 3. (The ring I tested for this comparison is a new one, so the battery should be in good shape.) Oura hasn't published data on battery longevity, but two years seems to be a typical lifespan. The gen 4 has not been in production long enough to know how it will perform with age.
Charging
Both rings charge the same way, but they can’t share chargers. Each ring comes with its own little charging stand, fit to the exact size of ring you bought. (Replacements run $50-60 for either model and need to be the correct size.)
There are no major differences in the function of the chargers, except that the Oura 4 comes with a USB-C to USB-C cable, where the Oura 3 charger came with USB-C (for the charger end) to USB-A (the big rectangular kind, to plug into your computer or adapter).
Accuracy
The new Oura ring is supposed to be more accurate than its predecessor—or at least more reliably accurate. That’s because of the new “smart sensing” algorithm, which the company says improves blood oxygen accuracy by 30%, and reduces gaps in daytime heart rate readings by 7%.
What is smart sensing?
Honestly, it’s hard to understand exactly what smart sensing is, but after asking a very patient Oura employee a lot of stupid questions (my specialty) I think I kind of get it. The ring has multiple sensors, which it uses to take readings from your finger. But people have different arrangements of blood vessels in their fingers, different configurations of fat and other tissues, and different skin tones. The ring also moves around during the day, as you’ll notice if you are, like I am, constantly straightening it. All of this can make it hard for the system to understand what it’s actually picking up.
“Smart sensing,” new with gen 4, refers to an algorithm that chooses which sensors to pull data from at any given time, adapting based on what gets the best readings. And the advantage for you, according to Oura’s research, is that you’ll get fewer gaps in your data and better battery life.
Importantly, you calibrate this system when you first set up your ring in the app. Make sure to put the ring on right-side-up—the indent should be at the bottom of your finger, near your palm—and from then on, the algorithm should be able to pick out the most accurate signals.
How gen 3 and gen 4 compare on accuracy
I believe the Oura team when they say they’ve put a lot of work into the accuracy of their algorithm, but if we’re being honest, I don’t see any major differences between the data I get from the gen 3 and gen 4 rings. That’s probably fine, actually—the differences are likely to be subtle, like picking up an extra data point here or there. So they wouldn’t necessarily be detectable in an N=1 experiment like the kind I can run on myself.
I graphed the data from both rings for about two weeks. (Some nights are missing because of a mistake on my part, but we still have 16 days of good data.) Often, the two rings gave exactly the same reading for resting heart rate (RHR) and heart rate variability (HRV). Sleep duration wasn’t as close, but both rings’ readings were usually within a few minutes of each other.
I’ve always felt that Oura is a lackluster workout tracker, and I almost didn’t want to bother with a workout heart rate comparison. But I figured I really should give the rings their best opportunity to shine, so I went for a run with both rings and compared their readings to a Coospo heart rate chest strap paired to a Garmin Forerunner 265S.
Sigh. I wasn’t expecting much, but I’m sorry to say both rings suck at this. The route and pace tracking use your phone GPS, which is never going to be as accurate as a smartwatch. The auto-detection means the start and stop times are up to Oura’s best guess. And when the app displays your heart rate zones, it uses an age-based formula that you cannot change. This is a poor decision and I’ve written about why.
Okay. But we’re here to compare gen 3 and gen 4. And I did actually notice a small difference between the two. The gen 3 ring showed my heart rate graph on one test as a rollercoaster, dipping up and down, where I know from the chest strap that my actual heart rate only had subtle fluctuations. The gen 4 ring picked up a graph that looks a lot more like the one from the chest strap. As a fitness tracker, both rings fall short; but as a test of heart rate accuracy, this experiment supports Oura’s claims. The gen 4 does seem to do a better job of sensing what’s going on in my body.
And the Winner Is...
The 4th generation Oura ring has a smoother fit, better battery life, more sizes, two ways to find your size, and as far as I can tell the company is correct that it has more robust accuracy on its sensor readings. If you’re buying a new Oura ring, you’re already paying hundreds of dollars between the hardware and the subscription fees. Pay the extra $100 to get the new ring.
Who shouldn’t listen to me? If you really want to save the $100, or if you prefer the look of the Heritage (the flat-top style only available in gen 3), or if you already have a gen 3 and are wondering if the upgrade is necessary—you’re not missing much by sticking with the older model. The only thing you’ll really notice is that you’ll have to charge it slightly more often.
But for the average Oura ring enjoyer, the improved features of the gen 4 are worth the money. The gen 4 is like the gen 3, but better. So that’s the one that gets my vote.
Beth Skwarecki is Lifehacker’s Senior Health Editor. She has a bachelor’s degree in biology, has written two books, and is a certified personal trainer. She’s been writing about health, fitness, and science for over a decade, and can front squat 225 pounds.
