Circular Ring 2 puts blood pressure sensing on your finger

Circular is a relatively small player in the smart ring segment, which is currently led by the likes of Oura, Samsung, and RingConn. Yet, following a not-so-good start,the company’s second-gen smart ring is setting some high benchmarks.

The Circular Ring 2, which recently smashed past its $1 million crowdfunding goal, has landed support for blood pressure sensing. The feature will be enabled via an OTA update later this year. In 2026, the company will also enable sensor-driven blood glucose trend analysis for its smart ring

How blood pressure sensing works on a ring?

“Unlike other wearables that rely solely on PPG sensors, Circular has combined ECG and PPG technology to enable spot blood pressure measurements, making it the first smart ring to achieve this level of accuracy,” says the company.

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Circular says the onboard sensor array measures Pulse Transit Time (PTT) to assess blood pressure futures. Users can take measurements lasting between 30 seconds to a couple of minutes, in order to check how their activity patterns affect blood pressure levels.

Now, it almost sounds too good to be true that a smart ring can measure blood pressure, but smartwatches from giants like Apple and Samsung haven’t been able to figure it out natively.

The underlying technology, however, is ready. It has been tested in clinical settings, and already been commercialized, too. Earlier this year, Novosound revealed a novel ultrasound blood pressure monitoring system, claiming that it was ready for watches and smart rings.

An approach validated by science

The PTT-based approach has been backed by scientific research as a non-invasive cuff-less technique for measuring blood pressure. This is what a research paper presented at the 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society says:

“It has been reported that the pulse transit time (PTT), the interval between the peak of the R-wave in electrocardiogram (ECG) and the fingertip photoplethysmogram (PPG), is related to arterial stiffness, and can be used to estimate the systolic blood pressure (SBP) and diastolic blood pressure (DBP).”

This approach may not be 100% accurate on its own, but when heart rate and blood pressure estimates are factored into the measurement process, the error margin is “significantly” reduced. Another paper published in the Hypertension Research journal discusses the efficacy of this PTT method for blood pressure evaluation.

The dawn of a new era for smart rings

The Circular Ring 2 is shaping up to be quite an innovation powerhouse in the smart ring segment. Armed with an ECG, PPG, and a temperature sensor, it can measure everything from heart rate and blood oxygen saturation levels to ECG activity and heart rate variation.

Touted to be the first FDA-cleared smart ring that offers an ECG measurement facility, it has also received regulatory clearance for detecting signs of AFib, a serious heart condition. Apple made waves when AFib detection landed on its smartwatches.

The Circular Ring 2 is currently available via Kickstarter, priced at $239 for early backers. The regular sticker price for this Titanium-made smartwatch is $549. That’s on the higher side, but a notable benefit is that there’s no subscription model involved, and all the features are available straight out of the box.