Yes, at rest and with care: a phone camera can pick up your pulse from your fingertip and estimate HRV, and in several studies the better apps came close to an ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG . Results vary a lot between apps and phones, and the reading only works if you sit still with your finger resting lightly on the lens.
How a camera reads your pulse
When you cover the camera and flash with your fingertip, the light shines into the skin. With each heartbeat, a little more blood flows into the fingertip and absorbs a little more light. The camera sees this as a tiny, regular change in brightness. This method is called photoplethysmography PPG An optical method that shines light into the skin and detects the pulse of blood with each heartbeat. Most watches, rings and phone-camera apps use it to estimate HRV. More about PPG (PPG), and it is the same idea a smartwatch or ring uses.
The app finds the peak of each pulse and measures the time from one peak to the next. Those pulse-to-pulse gaps stand in for the gaps between heartbeats on an ECG. From them, the app calculates a statistic such as RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next. It mainly reflects vagal activity. More about RMSSD . The lesson on how HRV is calculated walks through that step.
What the studies show
All four studies below tested people at rest.
- 29 healthy adults, 5 minutes at rest. A 2017 study recorded HRV at the same time with a smartphone camera, a chest strap and an ECG, during guided and normal breathing. Differences in RMSSD between the phone and the ECG were trivial, and the authors judged the agreement acceptable.
- 57 healthy adults, slow breathing. In a 2023 study (mean age 26.7, 70% women), people did five 5-minute slow-breathing exercises. For every breathing pace, camera and ECG readings of lnRMSSD lnRMSSD The natural logarithm of RMSSD. Taking the log evens out the spread of RMSSD values, which makes day-to-day changes easier to compare and analyze. More about lnRMSSD and other HRV measures agreed very closely (intraclass correlation above 0.90).
- Three apps, one phone. A 2021 study had five healthy young adults sit with an iPhone 8 camera on the index finger, compared with a multi-lead ECG. Two camera apps had average RMSSD errors of 8.71% and 9.43%. A third app had an average error of 112.36%.
- An older, slower camera. A 2015 study of 30 healthy adults lying down used a phone that filmed 20 to 30 frames per second. RMSSD from the camera rose and fell with the ECG value but did not agree closely enough to be swapped for it. The authors noted that this frame rate is often considered too low for HRV, although they argued that smoothing the signal can help.
Taken together, the studies show that a camera reading can be accurate when the app processes the signal well and the phone records fast enough. A good result from one app does not prove another app works.
What can go wrong
- Movement. Even small finger movements disturb the signal. A review of pulse sensors found that physical activity often made pulse-based HRV unacceptably different from ECG.
- Finger pressure. In the 2021 study, participants rested the camera on the finger so that it did not press down.
- Short recordings. The same study found that recording length affected accuracy more than the type of sensor. Its two weakest devices used 3-minute recordings instead of 5.
- Irregular beats. Extra or skipped beats distort HRV, which is why researchers remove them before calculating it. A camera app cannot tell you why your pulse is uneven.
How to get a usable reading
- Sit or lie down and rest for a minute or two first.
- Rest your fingertip over both the camera and the flash, without pressing.
- Keep your hand and phone still, supported on your leg or a table.
- Breathe normally and record for as long as the app allows, ideally a few minutes.
- Measure at the same time each day, such as just after waking, and watch the trend.
The lesson on taking a good HRV reading covers the routine in more detail. To compare a camera with other sensors, see is wrist HRV as accurate as a chest strap? and the how HRV is measured guide.
You can also enter a number from any camera app or wearable in the HRV checker.
When to talk to a doctor
A camera HRV reading is a wellness estimate. It cannot diagnose an irregular heart rhythm or any other condition. If you often feel a racing, fluttering or uneven heartbeat, or you have chest pain, dizziness, fainting or shortness of breath, talk to a doctor.