With the Welltory app, you can measure heart rate variability (HRV) using your smartphone camera, heart rate monitor, Apple Watch, or Samsung Watch. Variability measurement is not an electrocardiogram (ECG) recording; it cannot replace an ECG or a doctor's consultation. However, a study published in the scientific journal Elsevier proved that our variability measurement technology is as accurate as ECG monitors.
Principle of measurement with a smartphone camera
We use photoplethysmography (PPG), an optical method that measures changes in blood volume within vessels. This technique requires a light source and a photodetector, both conveniently available in a standard smartphone: the flashlight acts as the light source, and the camera serves as the photodetector.
The beating of your heart causes the measured changes. When your heart contracts, the capillaries in your fingertip fill with blood, leading to increased light absorption and darker images. When your heart relaxes, these capillaries contain less blood, resulting in brighter images.
Welltory's advanced algorithms have been trained to detect even the smallest fluctuations precisely. Research supports that this approach is accurate and user-friendly, effectively turning your smartphone into a robust tool for health analysis.
Choosing a camera for measurement
With no external devices connected, camera measurement will be set as default. Otherwise, Welltory will remember the last device you used. To switch back to the camera, head to Menu → Settings → Device or Menu → Settings → Primary Device.
If your phone camera has a green Connected status, it will be used to take measurements.
If your iPhone or iPad has Ultra Wide camera / Back Telephoto camera / Back camera, we recommend switching to it so that the quality of your measurements will be high. To change the camera, please open the app Settings → Measurement Device and select Ultra Wide camera / Back Telephoto camera / Back camera under Phone camera section.
Rules of quality measurement
To take an accurate camera measurement:
Make sure your phone has a flashlight.
Put your finger so that it covers both the camera and the flashlight.
Don’t press too tightly.
Don’t move your finger. Our algorithm analyzes the images it gets from the camera, and any movement can distort them.
Always use the same finger on the same hand.
If your measurements are inaccurate, please read the article «How to take accurate heart rate variability measurements». You will find tips to help you improve the quality of your measurements.
Smartphones that are suitable for camera measurement
All current iPhone models with a camera and flash are ideal for measurement:
iPhone X
iPhone 11, 11 Pro, 11 Pro Max
iPhone 12, 12 mini, 12 Pro, 12 Pro Max
iPhone 13, 13 mini, 13 Pro, 13 Pro Max
iPhone 14, 14 Plus, 14 Pro, 14 Pro Max
iPhone 15, 15 Plus, 15 Pro, 5 Pro Max
iPhone 16, 16 Plus, 16 Pro, 16 Pro Max
The iPad models are suitable for the measurements:
iPad Pro 11" 2nd gen
iPad Pro 11" 3rd gen
iPad Pro 12.9" 4th gen
iPad Pro 12.9" 5th gen
iPad Pro 12.9" 6th gen
iPad Pro 13" (M4)
All modern Samsung models in which the camera and flash are located at a small distance from each other are suitable for measuring. For example:
Samsung Galaxy A52, A52s, A53, A54
Samsung Galaxy A33, A34
Samsung Galaxy A72, A73
Samsung Galaxy S21, S21+, S21 Ultra
Samsung Galaxy S22, S22+, S22 Ultra
Samsung Galaxy S23, S23+, S23 Ultra
Smartphones that are not suitable for camera measurement
On some smartphones, the flash is too far from the camera, so it can't illuminate your finger enough during measurement. Such devices include, for example:
Google Pixel 6
Google Pixel 6A
Google Pixel 6 Pro
Google Pixel 7
Google Pixel 7 Pro
Oppo Reno 10x Zoom
You can't take measurements with the camera on these smartphones.
Measuring with different iPhone or iPad models
Measuring on iPhone X
When measuring on iPhone X, your finger should cover the bottom camera and flash. To measure, place your finger parallel to the camera unit, cover the cameras, and flash completely:
Measuring on iPhone 11
When measuring on iPhone 11, your finger should cover the bottom camera and flash. To measure, place your finger diagonally across the camera unit, cover the bottom camera, and flash:
Measuring on iPhone 12 and 12 mini
When measuring on iPhone 12, your finger should cover the top camera and flash. To measure, place your finger diagonally across the camera unit, cover the top camera, and flash:
Measuring on iPhone 13 and 13 mini, iPhone 14 and 14 Plus
When measuring on iPhone 13, 13mini, 14, and 14 Plus, your finger should cover the top camera and flash. To measure, place your finger perpendicular to the camera unit, cover the top camera, and flash:
Measuring on iPhone 15 and 15 Plus
When measuring on iPhone 15 and 15 Plus, your finger should cover the bottom camera and flash. To measure, place your finger parallel to the camera unit, cover the bottom camera, and flash:
Measuring on iPhone 16 and 16 Plus
When measuring on iPhone 16 and 16 Plus, your finger should cover the top camera and flash. To measure, place your finger diagonally across the camera unit and completely cover the top camera and flash:
Measuring on iPhone 11 Pro and Pro Max, iPhone 12 Pro and Pro Max, iPhone 13 Pro and Pro Max, iPhone 14 Pro and Pro Max, iPhone 15 Pro and Pro Max, iPhone 16 Pro and Pro Max
When measuring on the iPhone Pro and Pro Max models, your finger should cover the flash and single camera on the right side. To measure, place your finger parallel to the camera unit and cover the camera on the right and the flash:
Measuring on iPad Pro 11“ 2nd gen, iPad Pro 11” 3rd gen, iPad Pro 12.9“ 4th gen, iPad Pro 12.9” 5th gen, iPad Pro 12.9“ 6th gen, iPad Pro 13” (M4)
When measuring on iPad Pro models, your finger should cover the bottom camera and flash. To measure, place your finger diagonally across the camera unit, cover the bottom camera, and flash:
Measuring with different Samsung models
Measuring with Samsung Galaxy S21, S21+, S22, S22+, S22+, S23, and S23+
When measuring on the Samsung Galaxy S21 and S21+, your finger should cover the middle camera and flash. To measure, place your finger diagonally across the camera unit, cover the middle camera, and flash:
Measuring with Samsung Galaxy S21 Ultra, S22 Ultra, S23 Ultra
When measuring on the Samsung Galaxy S21 Ultra, and S22 Ultra, your finger should cover the camera in the middle and the flash. To take a measurement, position your finger diagonally across the camera unit, cover the middle camera, and flash:
Measurement problems
The flash burns
On some smartphones, the flash heats up too much and can burn you. In such cases, we recommend keeping your finger 2–3 mm away from it. However, make sure that it continues to touch the camera.
I don't know if I'm covering the right camera
When the measurement starts, you’ll see the image from the relevant camera on your phone’s screen. You're good to go if the screen is bright red (due to the flashlight illuminating your capillaries). If the screen shows your surroundings, your finger is on the wrong camera. Try putting it on each camera one by one until you see a red screen.
The smartphone camera is too far away from the flash
Usually, users encounter this issue on Android devices where the cameras and flash are far away from each other. We recommend using a compatible heart rate monitor or Samsung Watch for HRV measurements in such cases.
I can't take more than one measurement a day
In the Premium version, users can take unlimited measurements per day. However, you are limited to only one measurement with a camera or heart rate monitor per day in the free version. Once you have taken a measurement using a camera or heart rate monitor, the measurement button in the feed will become locked until 5 a.m. the following day:
The button loader visually indicates the remaining time until you can take another measurement. It automatically updates whenever you open your feed or relaunch the Welltory app.