COLMI R02 Review: The $40 Gateway Ring
Published: July 8, 2026
We independently test everything we recommend.
Buying through links on our site supports our work.
Let's set expectations before your money leaves your pocket. The COLMI R02 costs about $40, and it is not trying to be an Oura. What it is: the cheapest possible way to answer one question. Will you actually tolerate a ring on your finger all night, every night? For the price of two lunches, with no subscription, that's a genuinely useful thing to buy.
How accurate is a $40 smart ring, really?
Directionally accurate, and no more. Steps and heart rate are in the right ballpark. Sleep is where the price shows: the R02 largely measures how long you were in bed rather than how you actually slept, and REM detection is basically a guess. Do not make health decisions on this data. Treat the numbers as a rough trend line, not a truth, and you won't be disappointed.
So who should actually buy it?
The ring-curious. If you've never worn one and aren't sure the form factor works for you (whether you'll hate it typing, sleeping, at the gym), the R02 tells you for forty bucks instead of four hundred. The QRing app is free, there's no subscription, and IP68 means it survives handwashing. When you inevitably want real data, you'll upgrade with confidence, knowing the ring life suits you.
Specs, Pros & the Bottom Line
COLMI R02
The $40 ring for testing whether you'll wear one at all
- Our Rating: 3.5 / 5.0
- Price: ~$40
- Battery (tested): 3–4 days
- Weight: 3–4 g
- Subscription: None
- Water resistance: IP68 (splash only)
- Sizes: 6–13
Pros
- Costs about $40, less than a month of some gym memberships
- No subscription and the QRing app is free
- Good enough for steps, heart rate and a rough sleep total
Cons
- Sleep tracking logs time-in-bed, not real sleep stages
- Stainless steel, not titanium, so heavier and scratch-prone
- Data is directional at best; don't make health decisions on it
Do not buy this expecting Oura accuracy. The sleep tracking measures how long you were in bed more than how you actually slept, and REM detection is basically a guess. Judge it by what it is instead: a $40 experiment. If you've never worn a ring and aren't sure you'll tolerate one on your finger all night, the R02 answers that question for the price of a couple of lunches, with no subscription and a free app. When you inevitably want real data, you'll upgrade, and you'll know the form factor works for you. Buy it as a gateway drug, not a destination. The moment you're hooked, jump to the RingConn Gen 2 Air.
What to buy instead
The moment you're hooked (and you will be, or you won't, which is the whole point), jump to the RingConn Gen 2 Air for real accuracy at $199. If budget is tight but you want a step up from the R02 with a proper recovery score, the Amazfit Helio Ring is the bridge, sizing permitting.
The verdict
Judged as a serious health tracker, the COLMI R02 fails, and it was never trying to pass that test. Judged as a $40 experiment in whether smart rings are for you, it's close to perfect. Buy it as a gateway, not a destination, keep your expectations calibrated to the price, and it does exactly one job well.