How the camera heart rate monitor works
Every heartbeat pushes a small wave of blood into your fingertip. More blood absorbs more light, so the skin gets very slightly darker with each beat and lighter between beats. A camera can pick up this change even though your eye cannot. The method is called photoplethysmography (PPG), and it is the same principle a clip-on pulse oximeter or a smartwatch uses.
Press Start measuring and allow the camera. On a phone the page asks for the back camera and switches on the flash when the browser supports it (you can use Turn flash on / Turn flash off). Cover the lens with your fingertip. Once the page sees a red, evenly lit image for 1 second it waits 3 seconds for the picture to settle, then measures for 30 seconds. If your finger slips off for more than 1 second, the measurement starts again, because a gap would corrupt the signal. If you want other quick checks of your body at rest, try the breath hold test or the balance test. For numbers about your body size, the BMI calculator compares your weight with your height and the body fat calculator estimates your fat percentage from tape measurements.
Behind the scenes the page averages the red channel of every video frame, filters out slow drifts and fast flicker (it keeps only rhythms between 0.7 and 3.5 beats per second, about 42 to 210 bpm), and draws the cleaned pulse wave live. Your heart rate comes from the time between the peaks of that wave, checked against the rhythm found by autocorrelation. The video never leaves your device; it is analysed frame by frame in memory and not recorded.
How to get a clean reading
- Rest first. Sit for a few minutes, with your forearm supported on a table. Measuring right after climbing stairs tells you about the stairs.
- Press lightly. Pressing hard squeezes blood out of the fingertip and flattens the signal. Rest the soft pad of the finger on the lens and, on a phone, over the flash next to it.
- Add light on a laptop. A webcam has no flash. Hold a lamp or a phone torch behind your fingertip so light shines through it.
- Stay still and quiet. Talking, laughing or moving your hand shows up as noise.
- Warm hands. Cold fingers have less blood flow and give a weaker wave.
The Signal bar shows how regular the wave is on a 0–100 scale: 70 or more is good, 50 to 69 is fair, below 50 is weak. The page only shows a number when signal quality is at least 50, when at least 60 % of the beat intervals agree with each other, and when the peak count and the rhythm estimate agree within 12 %. Otherwise you get "No reliable reading this time" with three tips, because a wrong number is worse than no number.
What is a normal resting heart rate?
The American Heart Association describes a resting heart rate between 60 and 100 beats per minute as normal for most adults. That range is shaded on your result, on a scale from 40 to 140 bpm. Well-trained endurance athletes often rest below 60, and children have higher rates than adults.
Your result is saved in this browser with your last readings, shown as a small line chart, so you can see how your resting pulse changes from day to day. There is no personal best: a lower or higher number is not a score to beat. Resting heart rate moves with sleep, stress, caffeine, alcohol, illness, heat, dehydration and many medicines. Measure at the same time of day, for example in the morning after waking, to compare fairly.
How accurate is a phone camera pulse check?
Studies of smartphone apps that use the camera and a fingertip found that they can match validated devices in resting adults. In a meta-analysis, De Ridder and colleagues (2018) found no significant difference between smartphone PPG apps and validated methods in adults at rest with a normal heart rhythm, but noted that the apps were not validated in children. Coppetti and colleagues (2017) tested four apps on 108 patients and found large differences between apps: those that used a fingertip on the camera were clearly more accurate than those that read the face from a distance.
This page has not been clinically validated. Cameras, lenses, flashes and browsers differ, and webcams usually deliver a weaker signal than a phone with a flash. Treat the result as an estimate and compare it with a manual pulse count (count beats at your wrist for 30 seconds and double it) if you are unsure.
Limits and when to see a doctor
This is not a medical device and cannot detect heart rhythm problems. An irregular rhythm such as atrial fibrillation can make the reading fail or give a misleading number. Call emergency services straight away if you have chest pain, fainting, severe shortness of breath, or a racing or irregular heartbeat. See a doctor if your resting pulse is repeatedly above 100, or below 60 together with dizziness, fainting or unusual tiredness.
More tests like this are collected on the fitness tests page.
Sources
- American Heart Association. Target Heart Rates Chart (resting heart rate of 60 to 100 bpm for most adults). heart.org.
- Allen, J. (2007). Photoplethysmography and its application in clinical physiological measurement. Physiological Measurement, 28(3), R1–R39.
- Coppetti, T., et al. (2017). Accuracy of smartphone apps for heart rate measurement. European Journal of Preventive Cardiology, 24(12), 1287–1293.
- De Ridder, B., Van Rompaey, B., Kampen, J. K., Haine, S., & Dilles, T. (2018). Smartphone apps using photoplethysmography for heart rate monitoring: Meta-analysis. JMIR Cardio, 2(1), e4.
Frequently asked questions
Can I really check my heart rate with my phone camera?
Yes, in most cases. Your fingertip gets slightly darker with each heartbeat as blood flows in, and the camera picks up that change. Studies of fingertip camera apps found good agreement with validated devices in resting adults, but this page itself has not been clinically validated.
Does it work on a laptop or desktop webcam?
Often, yes. Put a fingertip over the webcam and shine a lamp or a phone torch through it from behind, because webcams have no flash. The signal is usually weaker than on a phone, so keep very still.
Why did I get no result?
The page shows a number only when the pulse wave is clear and regular. Pressing too hard, moving, talking, cold fingers or too little light are the usual causes. Press lightly, add light and stay still for the full 30 seconds.
What is a normal resting heart rate?
The American Heart Association describes 60 to 100 beats per minute as normal at rest for most adults. Trained athletes often rest below 60. Measure after a few minutes of sitting still for a fair comparison.
Is my video recorded or uploaded?
No. Each frame is analysed in your browser, in memory, and then discarded. Only the final number is saved in this browser so you can see your last results.
Can this detect atrial fibrillation or other rhythm problems?
No. It is not a medical device and cannot detect rhythm problems. An irregular rhythm may simply make the measurement fail. If your heartbeat feels irregular or very fast, see a doctor.
When should I get medical help?
Call emergency services at once for chest pain, fainting, severe shortness of breath or a racing or irregular heartbeat. See a doctor if your resting pulse is repeatedly above 100, or below 60 with dizziness or fainting.