The Oura Ring 4 Fixed My Sleep. Here's My Honest Review in 2025.

Cosmopolitan

22-07-2025

I love my Oura ring. Ask any of my friends and they'll tell you that it's become one of my main personality traits over the past year and a half, that if I had a cartoon character, she would have a gold ring on her pointer finger. I'm never seen without it (if I am, get ready to hear a panicked 'Wait… did I lose my Oura ring?' in three… two… one…) and the minimal weight slips below the level of consciousness so it's basically a part of me.
In the time since I last updated my 2023 review of the Gen 3 Oura ring, the company released a brand new iteration, the Oura 4. Checks out, as they've historically released a new version every three years. And because of the aforementioned making-it-my-whole-personality thing, I knew I had to do a full test of the new version. After wearing it for six months, I'm ready to give you my full, in-depth, scientifically-proven (okay, I'm not a scientist, but there's lots of ~health data~) review—it's broken down into sections that are easy to scroll through in case you're looking for something specific, with tons of pics and anecdotes about what I loved and didn't love.
Note: If you want a more in-depth walkthrough of how I picked out my ring and set it up, you can read the full breakdown in our Oura 3 review here. The fit metrics and process of ordering a size kit are both still the same, just make sure you're specifically ordering the Oura 4 size kit—either on their website or on Amazon!
So, the Oura Ring is a health tracker. But what does it actually track? 'The Oura Ring boasts temperature sensors, a suite of LED lights to measure heart rate and blood oxygen, and an activity accelerometer to provide you with accurate insights to support your overall health,' says Jason Russell, Oura's Senior Director of Product.
Once data is collected via the sensors, you're given three scores each day to help you interpret your stats at a glance: your Sleep Score, your Readiness Score, and your Activity Score. It's a number out of 100 that grades your sleep, your movement, and how prepared your body is to take on the day based on tons of data points from REM and deep sleep to heart rate variability and your body temperature while you're asleep. You also get a stress rating and resilience rating, and you can opt into Cycle Tracking as well.
While the basic concept and experience you know and love is still the same, there are a handful of useful new features that the Oura team rolled out with the fourth-generation ring. And pssst: While the new hardware features are unique to the 4, the software and app updates will be available for anyone with any version of the Oura Ring!
First up: Major redesign! The app used to have a fixed design but now, you'll see different stats and scores highlighted depending on what time of day you open up your app. Whatever is most helpful or notable will float up to the top throughout the day, whether it's an exceptional sleep score or an elevated body temperature. Huge news for anyone who doesn't want to get into the weeds of HRV charts and just wants to be given the most important highlights!
Visually, the bumpy domes on the inside of the Gen 3 have been removed and replaced with flat sensors for a more comfortable wearing experience. This new ring also has smart sensing and increased accuracy, which didn't pick up on any life changing new data so it wasn't a huge, measurable impact on my life, but someone who tracks their heart rate or body temperature more closely will appreciate this. I also find that the battery lasts a lot longer, allowing me to go several days without charging rather than having to juice it up every other day.
I was a perfect size 6 in the Gen 3, so I ordered the size 6 in the Gen 4, but that ended up being so loose that I was experiencing gaps in my data. I exchanged it for a size 5, which I wore on a smaller finger.
A word to the wise: Because the Oura 4 has flat sensors on the inside instead of the Oura 3's raised sensors, it's going to be slightly looser even if you get the same size you had before. Don't assume you'll be the same size in the newer Gen 4! To avoid this, order a sizing kit beforehand.
And if you have an older Oura ring that you're upgrading, transferring your data over is incredibly easy—just click on the battery signal in the top right corner of your app, hit 'Set up a new ring,' and follow the tutorial (it took me 30 seconds…max).
The Oura Ring 4 will cost $349 for Silver or Black, $399 or Brushed Silver or Stealth, or $499 for Gold or Rose Gold. In addition to that, there's a $5.99 monthly subscription cost to use the app that displays and interprets all of your data.
Would I say that's cheap? No. But the monthly subscription cost barely makes a dent compared to other health apps (WHOOP costs hundreds per year) so you're really just making a one time investment that you'll be able to wear for a couple years.
I'm not proud of it, but I used to check Instagram and TikTok first thing in the morning. Like, as soon as I opened my eyes. I can't say I've fully kicked the phone habit, but I'm no longer going straight to brain rot the second I'm awake, because now I check my Oura app as soon as I wake up to get the full download on my sleep.
When you wear the ring overnight, it collects data on when you fell asleep, what sleep stages you were in throughout the night, how your breathing, heart rate, and temperature changed through each phase, and how long you slept for. That's insanely valuable data, people, considering the fact that it's hard to monitor your own sleep while you're, well, asleep. Once you check your app in the morning, you'll receive a sleep score from 0-100 based on your numbers as well as whether your stats were higher, lower, or about on par with the usual. I found that I tended to average in the 80s, but it really depends on how stressed I am!
Oh, and your Oura Ring will track naps, too. Whether it's an accidental 30 minute couch snooze or your attempt at falling asleep in your dinky economy seat that only lasts 15 minutes, your ring will pick up on that and adjust your daily sleep score accordingly.
Ah, the elusive Readiness score. What does it actually mean to be ready? What is 75 points ready vs. 90 points ready? Do I have to cancel all of my plans if I wake up with a 56 as my readiness score?!
All good questions. To put it simply, it's a rating of how ready your body is to take on the day based on how well you've been sleeping and how your resting heart rate has been trending recently. If you've been clocking under six hours a night with a heart rate that won't calm down (a symptom that usually correlates with drinking, by the way!) your readiness score might be lower than usual.
This, paired with your Resilience level (which basically measures your current stress levels and how you're recovering from it), is a great indicator of how much your body is able to take on. But you don't have to be tied to it. Sometimes getting a great sweat in on a lower Readiness day helps me bounce back from it, whereas other times it's permission to skip that workout class and cancel your nighttime plans in order to get better recovery sleep. The Oura Ring is meant to make your life better—so think of a high Readiness score as an encouragement to try going the extra mile, and a low Readiness score as a reminder to be kind to yourself if things feel harder than usual.
When I reviewed the Oura 3, the weakest point was probably the fact that the old software would think that certain activities (walking, emptying the dishwasher, going up the stairs) were other activities (boxing, swimming, sports). But I can confidently say that the activity tracking on the new ring and new software has improved. It correctly picked up on the fact that I was boxing, skiing, and kayaking without me needing to manually tag each activity, and it's nice to be able to see my route and cardio zones via the Oura app when I (very occasionally) go on a run through Central Park.
In addition to activity detection and running features, the Oura Ring also tracks your steps and caloric expenditure, if you're into that kind of thing. I don't do a ton of cardio and I'm aware that as a New York City resident I clock plenty of steps per day, but it was nice to see the correlation between heavy activity days and how quickly I was able to fall asleep the following night.
The Oura Ring may not be the most comprehensive training tracker on the market. It doesn't claim to be! It is, however, hands down the best middle-of-the-road option out there. It's chic, non-intimidating and accessible, it looks pretty on your hand, and it gives you comprehensive activity data with zero pressure to close activity rings (you know what I'm talking about) or stand up every 30 minutes. It's perfect for someone like me, who wants to remain active and have a general awareness of it—but not at the cost of my sanity or how cute my accessories are.
I was confused about a lot of things during my teenage years, including my period, which was pretty high up on the blind-navigation list. Basically, it would come every 25-40 days, and it was a complete shock every time. But after learning how to track my cycle via body temperature over the past couple of years, I've gone from being like, 'My period is here AGAIN?!' to being like, 'Yeah I know I'm getting my period at some point today because my temperature dropped.'
Confused? Basically, your body temperature typically sits below baseline during the follicular phase (the first part of the menstrual cycle), spikes right around ovulation, and then sits above baseline during the luteal phase (the part of the menstrual cycle right before you bleed) until the day of your period when your temperature drops noticeably. The Oura Ring 4 takes your temperature every day and charts it so you can keep track of where you're at in your monthly cycle, which is, uh, SO much better than going into it blindly and then being stuck without a tampon in a public restroom while wearing white jeans. Just me?
This temperature data can also be used to estimate fertile days if you're trying to conceive or trying to avoid getting pregnant without being on hormonal birth control. I didn't find Oura's in-app ovulation and period prediction dates to be super accurate, if I'm being honest, but you can sign up for the Natural Cycles app (an FDA-cleared form of non-hormonal birth control) which integrates seamlessly with the Oura app. I found the Natural Cycles predictions to be much more accurate and consistent, and it's $119.99 per year, which comes out to just $9.99 a month.
The most important part of the entire review, if you ask me. I've tried so many different stacks, some out of necessity (because my ring is a little loose on certain fingers) and some for style purposes. My favorite compliment is 'Omg I didn't even notice you were wearing a health tracker, it blends right in with the rest of your jewelry!'. Here are some of the stacking rings I've invested in…
The complimentary rings I reach for the most often are these two Pavoi bands that went semi-viral on TikTok for being under $20 each. Tons of people started wearing these bands above and below their Oura ring for a shockingly luxe look—and yes, I can confirm that it's a totally seamless stack.
Alternatively, I love wearing my Oura ring with a solitaire crystal ring—my go-to is from Uno de 50 and currently sold out, but below are some alternatives as well as rings I tend to wear on other fingers! And lastly, I've found it really helpful to wear a thin chain around my neck for periods where I need to take my ring off but want to make sure I don't lose it, like when I'm getting a manicure or when I'm lifting weights and don't want the bar to scratch up the metal.
Okay, that was a lot of information! After testing out the Oura Ring 4 for six months I can confidently say that I'm a huge fan and love the product even more than I did before, but if you're still trying to digest all of that before making your decision, let's break it down into a simple pros and cons list...
Hannah Oh is a self-proclaimed nerd for biometrics and sleep optimization. Along with writing about the best sales and deals to spend your hard-earned money on, she has tested a variety of sleep-tracking devices and wearables on her quest to create the perfect bedroom sanctuary in the middle of noisy New York City. She is never seen without her Oura ring and has been known to tell strangers on the street why they should buy one, too.
Hannah is the Shopping Editor at Cosmopolitan, covering all things from chic home decor to trendy fashion finds, TikTok products that are actually worth your $$$, and the perfect gift to buy for your boyfriend's mom. She previously wrote for Seventeen and CR Fashion Book. Follow her on Instagram for hot takes on red carpet fashion and pictures of her office outfits that nobody asked for.