Colmi R02 vs Oura Ring: A Personal Comparison of a Cheap Smart Ring
Updated: 2026-09-25
Budget rings like the Colmi R02 promise sensors similar to Oura Ring's, for a fraction of the price. Health OS syncs both into the same underlying data store, which makes it possible to compare them directly on the same person. Below is a personal comparison: what actually matched, what didn't, and how that compares to research on Oura's own accuracy. This is one person's data, not a validation study.
What the Colmi R02 Is
The Colmi R02 is a budget smart ring with sleep, body-temperature, SpO2, and heart-rate sensors, connecting over Bluetooth Low Energy. This particular hardware revision (RT02CR_V3.1) unexpectedly includes a body-temperature sensor.
Health OS ingests Colmi data (currently via a test Android build) and stores it alongside Oura's, which makes it possible to compare them directly on the same person.
How the Comparison Works, and How Many Nights
As of writing, the Colmi R02 has synced data for 4 nights: June 7, 9, 10, and 11, 2026. Of those, a documented comparison against Oura exists for only one night — June 7; for the other three, Oura has no sleep record for that period (a gap in the ring's own Oura sync). This isn't a study or a sample — it's one person, effectively one comparable night.
On that night (June 7), the ring recorded: time in bed 9.32 h, light sleep 5.62 h (337 min), deep sleep 1.65 h (99 min), REM 1.47 h (88 min). The documented Oura comparison for the same night: deep sleep 93 min, REM 88 min, light sleep 327 min — the totals line up almost exactly.
What Matched, What Didn't
The sleep-stage totals were close to Oura's — REM matched minute for minute (88=88), deep and light sleep were off by 6–10 minutes. But phase timing is a different story: epoch-by-epoch agreement with Oura was around 48%, meaning the ring got the exact timing of a given stage wrong roughly half the time. The sleep/wake split was more reliable, at around 90% agreement.
The takeaway from this one comparison: the R02 is reasonably good at "how much" sleep and "asleep or not", not at "exactly when" deep sleep and REM occurred.
What the R02 Doesn't Give You, Compared to Oura
The ring has no sleep score, sleep latency, or overnight HRV — the protocol simply doesn't return those metrics. Temperature isn't a baseline deviation like Oura's; it's raw body temperature, checked against the readings shown in the QRing phone app (36.6–36.8°C).
SpO2 timing within its slot is approximate — the response format doesn't carry an exact interval. And the heart-rate log only fills up if continuous measurement is turned on in the QRing app; it's off by default, and without it the heart-rate log stays nearly empty.
How Accurate Is Oura Itself — Research Context
A meta-analysis of 6 studies (n = 388) found no statistically significant differences between Oura Ring and polysomnography/actigraphy for total sleep time, sleep efficiency, time awake during the night (WASO), sleep latency, or time in each stage (Khan et al., 2025).
But even validated devices show modest epoch-by-epoch agreement with the gold standard: in a clinical sleep-lab cohort, Oura matched polysomnography on sleep/wake about as well as earlier studies reported in healthy adults (roughly 85% of epochs), and on the four sleep stages in only 53% (Herberger et al., 2025).
A Connection Quirk Worth Knowing
The ring holds only one Bluetooth connection at a time: to sync data to a computer, it has to be free of the QRing phone app. That's a limitation of the ring itself, not a Health OS bug.
FAQ
Is the Colmi R02 a good Oura Ring alternative?
Depends what for. On overall sleep totals (how much sleep, how much deep/REM), the R02 was close to Oura in our one documented comparison, but it has no sleep score, no overnight HRV, and no sleep latency, and its phase timing is less accurate. It's more of a budget "how much did I sleep" tool than a full replacement.
How accurate is the Colmi R02, based on a real comparison?
In our one documented night comparison, sleep-stage totals nearly matched Oura (REM 88=88 minutes), but epoch-by-epoch timing agreement was around 48%. That's one comparison on one person, not a validation study, so it shouldn't be generalized.
How accurate is Oura Ring itself compared to polysomnography?
A meta-analysis of 6 studies found no significant differences in total sleep time, sleep efficiency, or time in each stage (Khan et al., 2025). At the same time, in a clinical cohort, epoch-by-epoch agreement on the four sleep stages was only around 53% (Herberger et al., 2025) — even validated devices have limited precision on phase timing.
Can I wear a Colmi R02 and an Oura Ring at the same time?
Physically, yes — they're two independent BLE devices. But the Colmi R02 only holds one Bluetooth connection: to sync it to a computer, the ring has to be free of the QRing phone app.
Does the Colmi R02 measure body temperature?
This particular hardware revision does. It's raw body temperature, not a baseline deviation like Oura's — the readings were checked against the QRing phone app (36.6–36.8°C).
Can you trust a ring like this for sleep tracking?
For the broad picture — how much and roughly how — probably yes, based on our comparison the stage totals were close to Oura. For pinpointing exactly when a given sleep stage happened, accuracy is limited. Even research-validated rings show only partial agreement with polysomnography on phase timing (see the Oura context above).