Oura Ring 4 vs Ultrahuman Ring AIR

Both rings have newer siblings. Oura sells Ring 4 while stock lasts, next to the smaller Ring 5, and by 19 September 2026 Ultrahuman’s US ring page had moved on to Ring PRO, with AIR still priced in its comparison table. If you’re weighing these two, you’re choosing between a heavier ring that lasts longer and a lighter one that may be hard to find.

The numbers

Spec	Oura Ring 4	Ultrahuman Ring AIR
US price, 19 September 2026	From $349 in Silver or Stealth; Gold $399–$499	$349 in Ultrahuman’s PRO and AIR table
Subscription	$5.99 a month or $69.99 a year; first month free for new members	No recurring fee for core data
Weight	3.3–5.2 g, by size	2.4 g
Thickness	About 2.88 mm; sensor dome recessed 0.3 mm	2.45 mm in the FAQ; 2.4 mm in the comparison table
Width	7.9 mm	Not published
Sizes	4–15, Ring 4 kit	5–14; R1 kit works; not Oura sizing
Battery	Typically 5–8 days	4–6 days, depending on use
Charging	Size-specific dock and USB cable; typically 20–80 minutes	Open wireless pad, no enclosed case; about 180 minutes from empty
Data held on the ring	Up to seven days	4 days
Water	100 m; no scuba; no more than 12 hours underwater	100 m; scuba allowed; avoid more than 30 minutes continuously underwater
Sensors	Smart Sensing: 3 photodetectors, 2 triple LEDs (red, green, infrared), temperature, accelerometer	PPG, temperature, 6-axis IMU, single-core processor
Phone	iOS 16 or later; Android 11 or later with Google Play; Bluetooth 5.0	Not published
Connection	Bluetooth Low Energy, airplane mode	Bluetooth Low Energy
Operating temperature	−10 to 54 °C or −10 to 52 °C	Not published
Finishes	Gold, Silver, Stealth	Raw Titanium, Aster Black, Matte Grey, Bionic Gold, Space Silver

Weight against stamina

AIR is the light one. Both of Ultrahuman’s pages put it at 2.4 grams, against Ring 4’s 3.3 to 5.2 grams, which varies by size, and that’s AIR’s clearest advantage.

Ring 4 wins on everything to do with charging. Oura estimates typically 5 to 8 days per charge for Ring 4, a range that depends on activity, settings, ring size and how old the battery is, and it recharges in typically 20 to 80 minutes on its dock. AIR manages 4 to 6 days depending on use, and its open wireless pad needs about 180 minutes to fill it from empty, with no case to top it up away from the wall. Ring 4 also stores a week of data to AIR’s four days, which matters if you’re away from your phone for a while.

The membership

Ring 4’s price is only the start, because most of its app sits behind Oura Membership, which stays with your account. Membership is what gets you sleep analysis, nighttime blood oxygen, 24-hour heart rate, dynamic activity goals and automatic activity detection; without it, Ring 4 is a much thinner app.

There’s no recurring fee for core data, according to Ultrahuman’s current FAQ. That FAQ is written for Ring PRO, so confirm the same terms on any AIR checkout you find. PowerPlugs, the paid extras on the PRO page, aren’t an AIR requirement.

Sizes and fit

Ring 4 runs from size 4 to 15, and it’s the Oura to get if you need a 4, 5, 14 or 15, because Ring 5 doesn’t come in those sizes. It uses Oura’s white sizers. AIR comes in Ultrahuman’s own sizes, 5 through 14, and an older R1 kit works for it.

Ring 4 is the thicker ring at about 2.88 millimeters, with a 7.9 millimeter width and its sensor dome recessed 0.3 millimeters. AIR is 2.45 millimeters thick in Ultrahuman’s FAQ from 11 June 2024 and 2.4 millimeters in its later comparison table, a twentieth of a millimeter apart. That FAQ also says AIR matches R1’s features, accuracy and battery, and lists R1 at 2.8 millimeters and 3.6 grams. Ultrahuman doesn’t give AIR’s width for the US; some non-US pages say 8.1 millimeters, with ranges that mix AIR and R1.

Ring 4 comes in Gold, Silver and Stealth, though Oura says stock varies. AIR’s finishes are Space Silver, Bionic Gold, Matte Grey, Aster Black and Raw Titanium. If you want an Oura in ceramic instead, that’s Oura Ring 4 Ceramic, a separate zirconia shell, 3.51 millimeters thick and 5.1 to 8.1 grams.

Water and the gym

Both claim 100 meters, or 328 feet, but the fine print points in opposite directions. Ultrahuman allows swimming, showering and scuba with AIR, but says to avoid continuous submersion of more than 30 minutes. Oura’s Ring 4 guidance permits water sports and the sauna, though not diving, and its general FAQs draw the line at scuba: showering, swimming, recreational diving and snorkeling are fine, as long as the ring doesn’t stay submerged past 12 hours.

Ultrahuman also warns against wearing AIR for heavy weight training, because of metal contact. Oura rates Ring 4 for −10 to 54 °C (14 to 129 °F) in its Ring 4 guidance and −10 to 52 °C (14 to 125 °F) in its general FAQs, and recommends charging at room temperature.

Sensors and phones

Oura calls Ring 4’s sensor platform Smart Sensing, an algorithm that, Oura says, adjusts to skin tone, finger structure and activity and manages battery as it goes. Underneath are two triple LEDs, three photodetectors, digital temperature sensing and an accelerometer, with nighttime blood oxygen read from the red and infrared light. AIR’s list is shorter: PPG, temperature, a 6-axis IMU and a single-core processor, with no photodetector count or LED colors from Ultrahuman.

Ring 4 works with iOS 16 or later, or Android 11 or later with Google Play, on a phone with Bluetooth 5.0. It talks to the phone over Bluetooth Low Energy, offers an airplane mode, and was on firmware 2.12.0 as of 17 June 2026. Ultrahuman gives no phone requirements or firmware version for AIR. Neither ring has a screen or works as a GPS watch, and Oura says Ring 4 isn’t a medical device.

Can you still buy AIR?

On 19 September 2026, Ring 4 cost $349 in Silver or Stealth and $399 to $499 in Gold. The same storefront also showed euro prices, from €265.30, so make sure you’re looking at dollars.

AIR’s $349 comes from the comparison table on Ultrahuman’s US Ring PRO page, and the US address for buying a ring showed Ring PRO, not AIR, that day. Trade-in offers in the 2024 FAQ aren’t a sign you can get one delivered in 2026. If both rings are for sale, the hardware costs the same and membership is the difference; if only Ring 4 is, the choice is made for you. Look at both stores again before you order.

If neither fits

For a smaller Oura in sizes 6 through 13, look at Oura Ring 5. For Ultrahuman’s longer battery and a travel case, that’s Ultrahuman Ring PRO, not AIR. And for a Galaxy phone owner who wants everything in Samsung Health, Samsung Galaxy Ring is the one to look at.