Blood pressure measurement with app, smartwatch, fitness tracker and co.

Measuring blood pressure without a cuff

Immer öfter kommen Geräte auf den Markt, die den Blutdruck messen können, ohne die dafür übliche Manschette zu benötigen. Diese Geräte haben die Form einer Uhr oder eines Armbandes. Anstatt mühsam ein Gerät anzulegen und beim Aufblasen der Manschette zuzusehen, kann der Blutdruck quasi ohne Aufwand direkt bestimmt werden. Man trägt das Gerät üblicherweise den ganzen Tag und hat auf diese Weise immer die Möglichkeit zur Messung, was einen perfekten Überblick für den eigenen Blutdruck bietet.

How does the measurement work?

These devices measure and analyze the pulse wave coming from the heart. What they determine is the pulse transit time (PTT). The higher the blood pressure, the stiffer the vessels and the faster the pulse wave travels. You can imagine it like a soccer ball that rolls more easily when it's pumped up tightly. In this way you can't directly measure the blood pressure itself, but you can detect changes in blood pressure. That's why these devices always need reference measurements. This technique has been researched for many years. Alternatively, photoplethysmographic (PPG) signals are used the OptiBP app, for example, uses this approach.

Unlike conventional cuff-based devices, for these new devices it doesn't matter whether the measurement point is at heart level or not. You just need to stay still while measuring. The devices often also have a sensor that detects movement and flags it as an error or discards the measurement.

Are the measurement results accurate?

You need to distinguish between two basic categories of these devices. There are very simple devices on the market that are usually very cheap. They offer a blood pressure measurement but are not certified as medical devices. The results are well completely useless. That's a gimmick that estimates your real blood pressure about as well as a roll of the dice.

But there are also devices that are approved as medical devices. In those cases, measurement accuracy has been validated. Examples include Samsung's Galaxy Watch devices, the Aktiia band (now called Hilo), or the OptiBP app.

These devices or apps usually need to be calibrated to the individual user. That means you measure with a standard cuff device and at the same time with the new device. Usually two or three measurements are required. This calibration has to be repeated regularly typically monthly. In between, you can conveniently measure without a cuff at any time.

How well does this work in practice?

Unfortunately we have to temper expectations. We tested a Samsung Galaxy Watch, the Hilo band and the OptiBP app in detail.

The good news: It actually works! You do see realistic readings and the normal fluctuations over the course of the day are clearly visible.

However, the measurements tend to hover around the values from the calibration. In our comparison we tested the Aktiia band against guideline-compliant home measurements over a week using data from a conventional cuff device. The deviation was 15 mmHg systolic and 4 mmHg diastolic. For the Galaxy Watch 3 we didn't run such an extensive test series, but in direct comparison with a cuff device and the watch the differences were sometimes noticeable. The OptiBP app showed deviations up to 12 mmHg systolic and 15 mmHg diastolic; after recalibration the diastolic deviation at least decreased significantly.

The standards DIN EN ISO 81060-3 or DIN EN ISO 81060-5 are intended for validating devices with continuous measurements. Since these devices are worn during everyday activities, they must provide accurate measurements even during movement and be able to monitor blood pressure reliably over longer periods. Samsung and the maker of Aktiia, however, used the DIN EN ISO 81060-2 standard for validation.

You can think of it simply like this: in a device test according to DIN EN ISO 81060-2 the blood pressure is measured manually as the reference and alternated several times with the device. During that series the values are usually quite close because there are no activities happening and the measurements are taken close together in time. For a cuff device that is enough as a test. But as mentioned, cuffless devices are calibrated. All they would then have to do is repeatedly show that calibration value unchanged and they would have a good chance of passing the test. That is simply unsuitable for making a statement about measurement quality.

Manufacturers like to advertise studies that are supposed to prove accuracy. You have to look at those closely. For example, we've seen a study where the test measurements were only done shortly after calibration. That doesn't tell you much about the quality of the measurements over time.

Study

An international review in JAMA Cardiology (April 2025) reached a sobering conclusion: so far no cuffless blood pressure device has passed the strict accuracy tests required for traditional upper-arm cuffs. Most models first need to be "set" with a conventional cuff and can then deviate by 510 mmHg from the true value especially if you move, exercise or sleep. Factors such as skin pigmentation, obesity, arterial stiffness, heart rhythm disturbances (arrhythmias) or tremor affect the optical sensors (PPG) in these devices and increase measurement errors. Such inaccuracies raise the risk of dosing blood pressure medications too high or too low. Experts therefore recommend, for the time being, using only devices that have been proven accurate in independent evaluations and to consider cuffless models as interesting but not yet mature supplements.

Result

If high values are measured during calibration, those will also appear in everyday use. If the calibration values are in the normal range, everyday measurements will also tend to be normal. That's still too much guesswork, estimation or chance to be truly useful. Especially with high blood pressure, readings can fluctuate more than the calibration of a cuffless device is willing or able to show.

In practice we tend to avoid the Aktiia band because it's uncomfortable to wear and, due to lack of waterproofing, often has to be taken off and put back on. For that you get little useful measurement data.

The Galaxy Watch is very usable as a smartwatch. Because the measurement results felt somewhat unreliable, we stopped doing regular measurements the function was effectively unused. When the watch then wanted to be recalibrated every month, we turned the function off rather than go through the hassle monthly for no benefit.

The OptiBP app would be convenient because you'd always have it with you. However, the ongoing subscription costs are too high given that the values are still too unreliable.

Conclusion July 2025: Unfortunately, for patients with high blood pressure there's still no way around the cuff.

In June 2025 the IEEE EMBS Symposium "Recent Advances in Cuffless Blood Pressure" took place, where the current state was discussed. We attended on your behalf. It became clear that the technology is not yet ready for broad clinical use as a replacement for traditional methods. Major reasons are fundamental challenges in validating accuracy, especially tracking blood pressure changes (trend-tracking) over different time periods. Experts stressed the need for strict, independent validation studies that go beyond point accuracy and demonstrate clinical relevance and improved patient outcomes. There is a clear need for medical approval for devices that provide blood pressure values. Clinical use will only be conceivable after these strict requirements are met, a clinical benefit is shown in outcome studies, and clear application guidelines have been established.

Hybrid between blood-pressure watch and smartwatch: Huawei Watch D

Huawei offers a true smartwatch, the Huawei Watch D, which additionally provides a blood pressure measurement with an integrated cuff. Because this is a cuff-based measurement similar to an ordinary device the comments above do not apply. More information in our article on blood pressure watches.

Measuring blood pressure with the camera

There are also providers who determine some vital signs, including blood pressure, from a 60-second video of the face. That's very innovative we therefore looked at the solution from Binah.ai. However, in our test the measured blood pressure was about 15 mmHg off compared with the cuff device. That's unfortunate, but that was the situation at the end of 2023. Maybe there will be better results in the future.

Sources:

This article comes from BloodPressureDB – the leading app since 2011 that helps hundreds of thousands monitor their blood pressure every day. Our content is based on carefully researched, evidence-based data and is continuously updated (as of 07/2025).

Author Horst Klier has been intensively involved with high blood pressure since 2002 initially from personal experience and, since 2009, as the developer of BloodPressureDB. Thanks to his app and specialist platform used by millions as well as numerous publications, he is now regarded as a recognised blood pressure expert. As the author of several health guides and professional articles, he makes complex information understandable and practical.