Blood pressure smartwatches work by using optical sensors and algorithms that measure changes in the blood flow under your skin.
When you wear the watch on your wrist, light from LEDs penetrates the skin and reflects back to the sensor. The watch then analyzes the variation in this reflection, which relates to your pulse wave. From the timing and shape of this wave, the smartwatch estimates your systolic and diastolic blood pressure.
Some models also require calibration with a traditional cuff monitor. You usually enter your real readings into the watch during setup, and the smartwatch uses this data as a baseline. After calibration, the device estimates your pressure without a cuff, but you need to recalibrate from time to time for accuracy.
Blood pressure monitoring is still limited to a smaller subset of smartwatch models and often needs regular calibration to stay useful.
Are blood pressure smartwatches accurate?
Blood pressure smartwatches have limited accuracy compared to traditional cuff-based monitors and cannot match clinical-grade precision.
Studies show that while some validated models like the HUAWEI WATCH D can meet international standards with mean differences of only -0.034 mm Hg for systolic pressure and -0.65 mm Hg for diastolic pressure, most smartwatches show systematic bias patterns.
Research demonstrates that these devices tend to overestimate low blood pressure readings and underestimate high readings. The Samsung Galaxy Watch Active 2, for example, showed sensitivity of 83% but specificity of only 41% for detecting hypertension, which means it correctly identifies high blood pressure 83% of the time but fails to rule out normal readings 59% of the time.
Do I need to calibrate my blood pressure smartwatch?
Yes, you need to calibrate your blood pressure smartwatch if you want accurate readings.
These watches use optical sensors that estimate blood pressure from pulse waves, but they need reference values from a traditional cuff monitor to stay precise. Without calibration, the readings can drift and give results that do not reflect your real blood pressure.
Most models require calibration when you first set them up, and some need recalibration every few weeks or months depending on the brand. You usually do this by measuring your blood pressure with a cuff monitor and entering the values into your smartwatch or its app. This step helps the watch adjust its algorithm to match your personal blood pressure pattern, so it can track changes more reliably over time.