Oura Ring 4 review: the best-validated ring, with a fee attached

How this review was built

We haven't worn, owned or lab-tested an Oura Ring 4. This is a research review: it's built from Oura's published specs, its membership and warranty terms, the peer-reviewed studies that tested the ring against a chest strap, and what named reviewers and reporters found, all linked in the sources at the bottom. The score comes from our published ring rubric, explained on the methodology page. The Oura Ring 4 lands at 6.0 out of 10: near the top of every ring we cover for accuracy evidence and sizing, and near the bottom for cost of ownership, because its membership has no end date.

Here's where it stands in September 2026. Oura announced Ring 5 on May 28, 2026 (TechCrunch). The Ring 4 product page is still live on Oura's site, but it shows no price, promotes Ring 5 and an upgrade FAQ, and the ring no longer appears on Oura's rings store list. It's still listed on Amazon.com, and Gizmodo reported an Amazon clearance discount on some Ring 4 finishes days after Ring 5 launched. We don't print hardware prices because they change daily; the card above links to the live listing. For every model we cover, start at the smart ring reviews hub.

What you pay over three years

A cheaper ring doesn't mean a cheaper Oura. The Ring 4 needs exactly the same membership as Ring 5, $5.99 a month or $69.99 a year in the US, and the fee runs for as long as you want the full app. Here it is next to the two alternatives on this page.

There's no way to buy your way out, either. Oura's support page says “There currently is no option to purchase or upgrade to a Lifetime Membership.” Some early Gen3 buyers kept grandfathered lifetime plans, and Gen2 owners don't need a membership at all, but neither helps someone buying a Ring 4 today. Our Oura membership cost breakdown runs the numbers for every billing option.

One partial offset: Oura says most items on its online store “can be purchased with HSA or FSA funds,” and a prepaid membership can be paid that way when it's bought with a new ring (Oura Support). That's Oura's own store, not Amazon, and whether your plan accepts it is between you and your plan administrator. Our HSA and FSA guide explains the IRS rule that decides it.

What's locked without the membership

The ring keeps measuring whether you pay or not. What changes is what you're allowed to see. Oura's own wording: without a membership, “you'll only be able to see your three daily Oura scores (Readiness, Activity, and Sleep), ring battery, basic profile information, app settings, and the Explore content” (Oura Support). Oura's store describes the membership as what “unlocks personalized insights, an AI health companion, and new features as they arrive.”

Read those two lines together and the trade is clear. Three summary numbers a day are free. The detail behind them, and anything Oura adds later, is rented. For a buyer who wants to own his sleep data outright, that's the whole objection to Oura, and it applies to the Ring 4 exactly as it does to Ring 5. If you already own an Oura and want to know how far the free tier goes, we cover that in using an Oura Ring without a subscription.

What the evidence says

This is where the Ring 4 earns its place. It's the ring generation tested in the best study we found for this site's core question, whether a ring can match a chest strap. Dial et al., published in Physiological Reports in 2025, compared Oura Gen 3 and Gen 4 with a Garmin Fenix 6, a Polar Grit X Pro and a WHOOP 4.0, using a Polar H10 chest strap as the reference, across 536 nights in 13 adults (Dial et al.). The Oura rings agreed with the strap most closely of all the devices tested. For the Gen 4, resting heart rate error (MAPE) was 1.94% and HRV error was 5.96%, with concordance of 0.98 and 0.99. The older Gen 3 came in at 7.15% for HRV.

Older Oura research points the same way, with limits. Cao et al. (JMIR, 2022) found an earlier Oura ring “could accurately measure nocturnal HR and RMSSD” against a chest ECG in 35 healthy adults, while its frequency-based HRV measures had high error. Liang et al. (Sensors, 2024) found strong agreement overall but higher HRV error in older adults. On sleep, the studies are mostly of the Gen 3: Svensson et al. (Sleep Medicine, 2024) reported sleep detection accuracy of about 91.7% against multi-night ambulatory polysomnography in 96 people, and a 2025 meta-analysis of six studies (Khan et al., OTO Open) found no statistically significant differences from sleep studies on total sleep time or time in each stage. A 2024 study by Robbins et al. reached similar conclusions but was funded by Oura, and a 2025 sleep-lab study (Herberger et al.) found group averages close to the lab but large errors for individuals. We found no sleep-staging study of the Ring 4 itself.

One more line matters for anyone buying for health reasons: no Oura ring feature is FDA-cleared. Oura is pursuing clearance for a blood pressure feature (MedTech Dive), but a ring's numbers are wellness data, not a diagnosis. Our smart ring HRV vs chest strap guide puts these figures next to every other ring's, and you can check your own ring with our chest-strap test.

Battery, sizing and phones

Battery. Oura says the Ring 4 “typically” lasts 5-8 days, the shortest claim of the three rings on this page, and there's no charging case in the box. Ring 5 claims 6-9 days; RingConn Gen 3 claims up to 14. Treat every one of those as the maker's figure under its own conditions. Our smart ring battery life guide reads each claim against what reviewers actually got.

Sizing. The Ring 4 runs from size 4 to 15, the widest range Oura sells, and the only Oura option if you wear a 4, 5, 14 or 15 (Ring 5 stops at 6-13). Oura warns that it uses “only whole sizes (no half sizes)” that “differ slightly from standard US ring sizes,” and that sizing “differs slightly between generations” (Oura Support). Ring 5's redesigned interior fits differently from Ring 4, so a Ring 5 sizing kit won't reliably size a Ring 4. Oura recommends the index finger for the best readings. Our smart ring sizing guide walks through the process, and rings in large and small sizes covers the edges of the range.

Phones and build. It works with iOS and Android. It's titanium with a PVD or DLC coating, water-rated to 100 m (328 ft), and Oura calls it “suitable for sauna and water sports but not diving.” There's also a Ring 4 Ceramic: a zirconia ceramic shell over a titanium inner shell, the same 5-8 day battery claim and sizes 4-15, per Oura and TechCrunch. Its product page was live with no price when we checked.

Warranty and the battery question

Oura's US warranty runs “One year from the date of purchase,” and it excludes batteries as consumable parts. We found no battery replacement program described, and refurbished units carry a 90-day limited warranty (Oura Support). The battery itself is sealed: Oura's safety page describes a “rechargeable, non-replaceable” lithium polymer cell of 15-22 mAh depending on size.

That exclusion deserves more attention on the Ring 4 than on most rings. Android Authority reported in September 2026 that Oura's pre-IPO filing disclosed an “$84.4 million increase in warranty expenses during fiscal 2025” tied to Ring 4 battery problems (Android Authority). The article describes battery performance problems, not swelling, and it doesn't tell you how any single ring will age. But if you're buying a Ring 4 on clearance, buy it somewhere with a return window you trust, and keep the receipt. Our guides to smart ring battery lifespan and warranties and returns compare every brand's terms.

Ring 4 or Ring 5?

If you've decided to pay Oura's membership, the choice comes down to three things. The Ring 4 has the direct evidence: it's the Gen 4 in the Dial study, while Ring 5 hasn't been through a published study yet. The Ring 4 has the size range: 4-15 against Ring 5's 6-13. Ring 5 has the longer battery claim (6-9 days against 5-8) and it's the model Oura currently sells, while the battery warranty report above concerned the Ring 4. The membership is identical on both, so it doesn't tip the decision. Our Oura Ring 4 vs 5 comparison goes spec by spec, and the Oura Ring 5 review covers the newer ring in full.

Who should skip it

• Anyone who won't pay a monthly or yearly fee. Without the membership you get three daily scores. That's the deal-breaker for most readers of this site, and no clearance price changes it.
• People who hate charging. 5-8 days is the shortest claim here, with no case to top it up on the road.
• Anyone who wants the battery covered. Oura's warranty excludes batteries, and the Ring 4 is the generation with the reported battery warranty costs.
• Anyone who wants a medical reading. No Oura feature is FDA-cleared.

If the fee is your sticking point, our best smart rings without a subscription ranks every no-fee ring on cost, evidence, battery and sizing.

The alternatives

RingConn Gen 3 is the pick if you want to stop paying. RingConn sells no subscription on any ring, claims up to 14 days a charge plus 150+ days with its charging case, and makes sizes 6-15. What it doesn't have is the Ring 4's evidence: we found no published validation of Gen 3 itself, and it showed “Out of stock” on RingConn's own store when we checked, though it was listed on Amazon. Our RingConn Gen 3 review has the details, and Oura vs RingConn puts the fee next to the evidence.

Oura Ring 5 is the pick if you'll pay the membership anyway and want Oura's current hardware, with a longer battery claim and a design Oura is still selling. For every ring in one table, see the smart ring comparison chart.