Smart Rings / Circular
Circular Ring 2 (2025)
The only FDA-cleared AFib ring — attached to the buggiest app in the category.
Overall score 7.1/10
Pros
- + The only ring here with real ECG electrodes and an FDA clearance for AFib detection
- + Digital sizing by phone camera removes the one-to-two-week sizing-kit wait every rival imposes
- + $299 with no mandatory subscription, against $608.97 over three years for a base Oura Ring 5
- + Advanced screens are earned by wearing the ring rather than billed monthly
Cons
- − The app is the weak link: Tom's Guide hit sync failures that lost sleep reports outright, and could not get the ECG feature to run during testing
- − Circular has announced a future premium tier for glucose and blood pressure with no price or date, so the no-subscription promise is not locked in
- − Water rating is half the category norm, and sources disagree on whether it is 50m or IP68-only
- − Titanium finish was described as scratch-prone, and the interior sensors protrude enough to leave marks on the finger
- − Fitness tracking is thin next to Samsung and Oura — this ring is aimed at cardiac screening, not training
Circular Ring 2 (2025) review: what the specs say
The only FDA-cleared AFib ring — attached to the buggiest app in the category. At $299, Circular's 2025 model sits in the middle of the range — the smart Rings we compare run from $149.99 to $479. It scores 7.1/10 overall, calculated from published specifications across 8 categories rather than from a subjective impression.
Its strongest showing is Health Sensing at 8.5/10 — what the sensors genuinely measure — heart rate, SpO2, temperature, ECG — rather than infer. The weakest is App & Data at 4.5/10, which is the trade-off to weigh before buying: if that is the specification you care about most, one of the alternatives below will serve you better.
Worth knowing before you buy: the app is the weak link: Tom's Guide hit sync failures that lost sleep reports outright, and could not get the ECG feature to run during testing; and circular has announced a future premium tier for glucose and blood pressure with no price or date, so the no-subscription promise is not locked in. Every specification on this page comes from Circular's own documentation or a verified retail listing — where a figure is not published, the table says so rather than estimating it.
Specifications and price last verified . Report an error
Full Specifications
| Battery Life (claimed) | 8 days |
| Battery, In Practice | Circular publishes two numbers, not one: 8 days in power mode and 5 days in performance mode — performance mode is the one that samples more often. Tom's Guide's tester got a week or more in practice. |
| Subscription | No mandatory subscription today; core features come with the ring, and some advanced screens are unlocked with in-app coins earned by wearing it. Circular has said a premium tier covering blood glucose and blood pressure is coming, with neither price nor date published — so the no-subscription position is provisional, not guaranteed. |
| 3-Year Cost of Ownership | 299 $ |
| Sizes Offered | US 6-14 |
| Sizing Kit | Two routes: a camera-and-credit-card digital sizing flow that needs no kit at all, or a $5 physical replica-ring kit. This is the only brand here that lets you skip the kit wait entirely. |
| Returns & Size Exchange | 14-day no-questions-asked return policy, 1-year warranty (2 years in the EU). |
| Measured vs Inferred | The only ring in this comparison with actual ECG electrodes: a 40-second single-lead reading screened for atrial fibrillation. Everything else — the 140+ 'biosignals' across 13+ health features — is derived from the same PPG, temperature and motion stack every other ring uses. |
| FDA Clearance | Circular states, and Tom's Guide's review confirms, that the ring is FDA-cleared to monitor for irregular heartbeats indicating AFib. That clearance covers the AFib feature, not the other 140 biosignals. |
| Water Rating | Sources conflict: Circular's own store page lists IP68 only, while Tom's Guide's review states 50m water resistance with IP68 — either way, half the 100m rating Oura and RingConn claim |
| Phone Support | iOS and Android |
| Charger & Data Export | Proprietary charger. Export: not published by the manufacturer. Tom's Guide reported sync failures that lost whole nights of sleep data, so what reaches the app is not always complete. |
| Connectivity | Bluetooth Low Energy (version not published by Circular) |
| Material | Titanium body with a hypoallergenic interior; 3g, 2.55mm thick |
| Warranty | 12 months |
Compare Circular Ring 2 (2025) With
Cheaper Alternative
RingConn Gen 2 (2024) — $269.00
Premium Alternative
RingConn Gen 3 (2026) — $349.00