Hot on the heels of its Circular Ring 3 announcement, Circular is rolling out a major health-tracking upgrade to its predecessor: on-demand blood pressure estimation for the Circular Ring 2.
The new feature delivers estimated systolic and diastolic readings directly from the finger in roughly 60 seconds—no bulky, inflatable arm cuffs required for everyday checks.
How It Works: Cuffless PWTT Tracking
Traditional cuffs measure blood pressure by physically compressing an artery until blood flow stops. Circular takes an optical and electrical approach instead, using Pulse Wave Transit Time (PWTT):
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Dual-Signal Capture: The ring simultaneously records ECG (electrocardiogram) and PPG (photoplethysmography) signals.
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Speed Over Pressure: It measures the fraction of a second it takes for a pulse wave generated by a heartbeat to reach your finger. Because pulse waves travel faster through stiffer, higher-pressure arteries, the algorithm translates transit velocity into estimated blood pressure.
Calibration and Daily Use
Because arterial stiffness varies from person to person, initial calibration against a reference standard is required:
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Set the Baseline: Log three separate readings from a traditional blood pressure cuff into the Circular companion app.
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Take a Reading: Touch the outer sensor of the Ring 2 with a finger from your opposite hand to close the ECG circuit. Hold still while the ring captures 20 clean, consecutive heartbeats alongside optical PPG data.
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Recalibrate Monthly: Circular recommends re-checking against a physical cuff every 30 days to keep baseline drift in check.
Availability
The blood pressure tracking update is available immediately via the Circular app at no additional charge—no paywalls or hardware add-ons required.