How to Measure Your Pulse With Your Phone Camera

How does a phone camera measure your pulse?

The technique is called photoplethysmography, usually shortened to PPG. It is the same principle behind the sensor on the back of a smartwatch and the clip a nurse puts on your finger.

Here is what happens during a reading:

1. The flash lights up your fingertip. Light travels into the skin and some of it scatters back toward the lens.
2. Blood absorbs part of that light. Each heartbeat pushes a small surge of blood into the tiny vessels of your fingertip, so a little more light is absorbed, then a little less as the pulse passes.
3. The camera records the changes. Researchers describe the PPG signal as two parts: a steady part from skin and tissue, and a small pulsing part that rises and falls with every heartbeat.
4. The app finds the beats. Software filters out the steady part and the noise, marks each peak of the pulsing part, and works out how many peaks fit into a minute.

The pulsing part is tiny compared with the steady part. That is why a still hand and good contact matter so much. A small wobble can be bigger than the heartbeat itself.

How do you measure your pulse with a phone camera?

This routine works with any fingertip camera app. The examples use Pulse Tracker.

1. Sit and rest for five minutes. For a resting number, sit quietly first. First thing in the morning, before coffee, is ideal.
2. Warm your hands. Cold fingers have less blood flow near the surface, which weakens the signal. Rub them together or hold a warm mug.
3. Find the rear camera and flash. On phones with several lenses, cover the main lens and the flash together.
4. Rest your fingertip lightly on top. Cover the lens and flash completely, with no gaps for outside light. Do not press down.
5. Rest your hand on a table. Brace your elbow or wrist so neither the phone nor your finger moves.
6. Breathe normally and stay quiet for about 30 seconds. Talking and laughing move your hand and change your breathing.
7. Check the signal before you trust the number. Pulse Tracker draws a live pulse wave and gives each reading a quality score. A clean wave has regular, even peaks. If the wave looks jagged or the score is low, reposition and try again.
8. Save and repeat at the same time each day. One reading is a snapshot. A daily habit builds a trend, and Pulse Tracker compares each new reading with your 30-day baseline.

How accurate is a phone camera pulse reading?

For fingertip methods at rest, the research is encouraging, with real caveats.

• A 2017 study in the European Journal of Preventive Cardiology tested four iPhone apps in 108 patients against ECG. The two fingertip apps beat the two face-scanning apps, with average errors of about 2 and 4.5 beats per minute versus about 7 and 8. The gap between the two fingertip apps also shows that the software matters.
• A 2022 study in Communications Medicine tested a fingertip-on-camera method in 95 people at rest and after exercise. It reported an average error of 1.6 percent, with similar results across skin tone groups.
• A 2024 scoping review in Frontiers in Digital Health found that contact smartphone PPG agreed with ECG for resting heart rate, but noted that most studies were done under tightly controlled conditions.

These numbers describe the specific methods that were studied, not every app. The practical takeaway: put your finger on the camera rather than scanning your face, and use good technique.

Why is my camera pulse reading wrong?

Most odd readings come from a handful of fixable problems.

What you notice	Likely cause	What to do
Reading never starts or keeps restarting	Lens or flash not fully covered	Slide your finger so it covers both, with no light leaking in
Number jumps around	Hand or phone moving	Rest your hand on a table and stay quiet
Weak, flat pulse wave	Cold fingers or pressing too hard	Warm your hands and lighten your touch
Much higher than expected	You were not truly resting	Sit for five minutes and measure again
Wave looks noisy outdoors	Bright sunlight around your finger	Move to a shaded spot indoors
Camera area feels warm	The flash stays on during the reading	This is normal; let the phone cool between readings

How can you double-check a camera reading?

Count your pulse by hand. Mayo Clinic suggests placing the tips of your index and middle fingers on the thumb side of your wrist, between the wrist bone and the tendon. Press gently, count the beats for 60 seconds, or count for 15 seconds and multiply by four.

If the hand count and the camera reading land within a few beats of each other, your technique is working. If you prefer tapping to counting, our BPM counter turns your taps into beats per minute.

What can a phone camera not tell you?

A camera reading is a wellness check, and it helps to be clear about its limits.

• Spot checks only. There is no continuous tracking through the day or during sleep. For that, you need a wearable. Our guide to heart rate apps without an Apple Watch compares the options.
• Not blood pressure or oxygen. Use your own home cuff and pulse oximeter for those. Pulse Tracker lets you log cuff readings, each placed in its American Heart Association stage, and log oxygen readings from your oximeter. After cuff calibration it can also show a clearly labeled blood pressure estimate, which is not a substitute for the cuff.
• Not a diagnosis. A camera reading cannot tell you why your heart rate is high or low. Pulse Tracker’s rhythm label simply describes whether a reading falls in a slow, normal or fast range.

From the same fingertip reading, Pulse Tracker also shows heart rate variability (RMSSD, SDNN and pNN50), respiratory rate, and stress and energy scores. Our HRV guide explains what those numbers mean. Heart rate measurement is free and unlimited.

What is a normal pulse reading?

For most adults, the American Heart Association puts a normal resting heart rate between 60 and 100 beats per minute. Well-trained athletes often sit lower. Your own trend over weeks says more than any single reading. See our normal resting heart rate guide for more detail.

When to see a doctor

Use your camera readings as a reason to start a conversation, not to end one. Make an appointment if:

• Your resting pulse is often above 100 or below 60 and you are not an endurance athlete.
• Your usual resting number changes noticeably without a clear reason.
• You often feel your heart racing, pounding, fluttering or skipping.
• You feel dizzy, faint or unusually short of breath with everyday activity.

If you have a heart condition or take medication that affects heart rate, talk to your doctor about what range is right for you.

Call emergency services (911 in the US) right away if a fast, slow or irregular heartbeat comes with chest pain or pressure, severe shortness of breath, fainting, sudden weakness or confusion. Do not stop to take another reading first.

Sources

• American Heart Association, All About Heart Rate (Pulse)
• Mayo Clinic, How to take your pulse
• Ryals S, Chiang A, et al. Photoplethysmography: new applications for an old technology, a sleep technology review. Journal of Clinical Sleep Medicine, 2023.
• Coppetti T, et al. Accuracy of smartphone apps for heart rate measurement. European Journal of Preventive Cardiology, 2017.
• Bae S, et al. Prospective validation of smartphone-based heart rate and respiratory rate measurement algorithms. Communications Medicine, 2022.
• Mather J, Hayes L, Mair J, Sculthorpe N. Validity of resting heart rate derived from contact-based smartphone photoplethysmography compared with electrocardiography: a scoping review. Frontiers in Digital Health, 2024.

Related: Can You Use a Heart Rate App Without an Apple Watch? · How to measure heart rate on iPhone · Normal resting heart rate by age · /tools/bpm-counter/

Wellness disclaimer. Pulse Tracker is intended for general wellness use only. It is not a medical device, is not FDA cleared or approved, and is not intended to diagnose, treat, cure or prevent any disease or condition. Blood pressure shown in the app is either a value you entered from your own cuff or an estimate derived from the pulse signal after cuff calibration; it is not a measurement and must not be used to make medical decisions. Read the full wellness disclaimer. Camera readings, estimates and classifications are for general information only and can be affected by movement, lighting, skin temperature and other factors. Do not use them to diagnose, treat or make decisions about a medical condition. Always consult a qualified healthcare professional, and call emergency services if you have chest pain, shortness of breath, fainting or other urgent symptoms.