Is my Oura Ring 4 size the same as the Oura Ring 5?

Do I really need a new sizing kit for the Oura Ring 5 if I already own one?

Oura Ring 5 is 40% thinner, but don’t reuse your old size! Discover why new sensors change the fit and how to track vital nighttime blood pressure signals.

Key Takeaways

What: Oura Ring 5 is a 40% smaller smart ring with redesigned, flattened sensor architecture.
Why: It monitors nighttime blood pressure signals and metabolic health trends with 6–9 days of battery life.
How: Use the new sizing kit; re-engineered internal dimensions mean your previous Oura Ring size is likely inaccurate.

The Oura Ring 5 has arrived, and while the 40% reduction in size is what catches the eye, the real story is hidden on the inside of the band. If you have worn an Oura Ring for years, you likely have your size memorized. But here is the catch: your old size probably won’t fit.

The Engineering Shift: Why You Need a New Sizing Kit

The most significant change in this generation isn’t just that it’s thinner—it’s how the internal sensors were built. In previous models, the sensors sat in small bumps that pressed into your skin. To get the Ring 5 down to 6.09mm wide and 2.28mm thick, those sensors had to be completely flattened.

Because the interior geometry has changed from a “bumpy” circle to a smooth, flat one, the way it interacts with your finger is different. This leads to a counter-intuitive reality: even though the device is 40% smaller, many users find they actually need a larger size than before. For example, a long-time size 11 user might now find a size 12 provides the most accurate sensor readings. The takeaway is simple: do not skip the sizing kit, even if you’ve been a loyal user since Gen 3.

Nighttime Blood Pressure Signals

Oura is moving away from the idea of “spot checks” and toward continuous, passive monitoring through its new Health Radar platform. Instead of using a traditional arm cuff, the Ring 5 monitors nighttime blood pressure signals while you sleep.

The logic here is that your body tells its clearest cardiovascular story at night. During the day, stress, caffeine, and movement create “noise” in your data. At night, your blood pressure should naturally drop. If it doesn’t, the Health Radar identifies that “non-dipping” pattern as a sign of cardiovascular strain, letting you see risks that a daytime doctor’s visit might miss. It’s not a medical replacement for a cuff, but it is a way to see the long-term trends of your heart health without lifting a finger.

Metabolic Health and the GLP-1 Journey

With the massive rise in GLP-1 medication use for weight management, Oura has integrated a specific tracking feature for these journeys. The app now allows you to log dosages and side effects alongside your biometric data.

This creates a “longitudinal view” of how the medication is actually affecting your body. You can see how a specific dose correlates with your sleep quality, resting heart rate, and activity levels. By importing lab results directly into the app through the new Personal Health Record feature, you can see your blood biomarkers right next to your ring’s data for a full picture of your metabolic health.

Durability and Aesthetic Refinements

The Ring 5 is built from titanium, but with a new focus on scratch resistance—a common pain point for smart ring owners who lift weights or work with their hands. The design is now a smooth, continuous curve that feels more like a traditional wedding band than a piece of hardware.

The color palette has been updated as well. While the classics like Silver, Black, and Stealth return, the Gold finish has been lightened to a more modern, jewelry-like tone. There is also a new “Deep Rose” finish, which leans toward a gender-neutral copper color. Despite the smaller frame, it maintains an IP68 rating, meaning it is safe for swimming or showering up to 100 meters.

The Ecosystem: AI Care and Battery Life

One of the biggest hurdles in shrinking a wearable is the battery. Surprisingly, Oura managed to increase battery life to 6–9 days on a single charge. If you are traveling, there is a new $99 anodized aluminum charging case that holds enough power to keep the ring running for an entire month.

The software is also getting smarter through partnerships with clinical leaders. A collaboration with ResMed allows users to take action on breathing disturbances identified by the ring to get professional sleep disorder diagnoses. Additionally, a partnership with Counsel Health brings AI-enabled care and access to licensed physicians directly into the Oura app, allowing you to ask health questions based on your personal data.

Investment and Subscription

The Oura Ring 5 starts at $399 for standard finishes and goes up to $499 for premium options like Gold or Deep Rose. To access the full suite of health insights, a membership is still required at $5.99 per month or $69.99 per year.

As the company prepares for a potential IPO with projected sales of $2 billion by 2026, the Ring 5 represents a shift from being a simple tracker to a comprehensive health intelligence platform. Pre-orders are open now, and shipping begins on June 4.