Can a phone camera really measure heart rate?

Yes. When you cover the camera lens and flash with a fingertip, the amount of blood in your finger changes with each heartbeat and the brightness of the red image flickers very slightly. This signal (photoplethysmography, PPG) is the same principle used by smartwatch heart rate sensors, and if you stay still with your finger steady, the result is close to a pulse counted at the wrist. Pressing too hard, cold hands or movement weaken the signal and make the reading less reliable.

Does it work on iPhone? The flash does not turn on.

Yes. Safari on iPhone does not let web pages turn on the flash, so it measures without it. In a bright room or by a window, cover the rear camera lens with the pad of your finger so that light shines through your finger and the circle on screen looks red. In a dark place the signal becomes weak; use the “By hand” tab instead.

Is counting your pulse for 15 seconds and multiplying by 4 accurate?

It is good enough for an everyday resting check. However, miscounting by one beat changes the result by 4 bpm, and the error grows if your pulse is irregular. When accuracy matters or your heart seems to skip beats, count for 60 seconds. Right after exercise your pulse starts falling quickly, so counting for 10 seconds and multiplying by 6 is common.

What is a normal resting heart rate?

For adults, 60–100 beats per minute is the usual range. Children are faster: about 70–120 at school age, 80–140 for toddlers and 100–160 for infants. People who do endurance training, such as runners, may be in the 40s or 50s. For comparable day-to-day numbers, measure after waking and using the toilet, once you have sat quietly for 1–2 minutes.

How do I calculate my target heart rate with the Karvonen formula?

Use “(maximum heart rate − resting heart rate) × intensity + resting heart rate”. For example, at 40 years old with a resting heart rate of 65 bpm, maximum heart rate is 220 − 40 = 180 and heart rate reserve is 180 − 65 = 115, so the target at 60% intensity is 115 × 0.6 + 65 = 134 bpm. Enter your age and resting heart rate on the “Heart rate zones” tab to list all five zones.

What heart rate is best for burning fat (zone 2)?

Zone 2 is generally 60–70% intensity by the Karvonen method (around 70% of maximum heart rate) — an effort you can keep up while holding a conversation, at which a larger share of energy comes from fat. For a 40-year-old with a resting rate of 65 bpm it is about 134–146 bpm. Higher intensities use a larger share of carbohydrate but burn more calories overall, so choose according to your goal.

What should I do if the reading looks wrong?

If the signal quality says “weak”, lightly reposition your finger, rest your elbow on a table and keep your hand still, then measure again. Pressing hard restricts blood flow and makes the wave smaller. Warm your hands first if they are cold. If it still does not match, compare it with your wrist pulse on the “By hand” tab.

Is the camera image sent anywhere?

No. The image is only used on your device to work out the average brightness of each frame; it is never saved as a picture or sent to a server. The log is stored only in this browser (localStorage).

Heart Rate Monitor | Measure Your Pulse by Placing a Finger on Your Phone Camera, a 15-Second × 4 Pulse Count Timer and Tap Counter, Karvonen Target Heart Rate and Training Zones, and Resting Heart Rate Ranges by Age with a Log

This heart rate monitor is a free tool that measures your pulse (beats per minute) when you gently cover your phone's rear camera lens and flash with your index finger. The amount of blood in your fingertip rises slightly with every heartbeat, so the red image the camera sees gets a little darker. The tool resamples that brightness at 30 points per second, removes slow drift, and finds your heart rate both from the strongest rhythm between 40 and 200 bpm and from the spacing between the peaks of the wave (photoplethysmography, or PPG — the same principle as an optical smartwatch heart rate sensor). While measuring it shows the pulse waveform with a mark on every detected beat and a signal quality rating (good, fair, weak), and starts again automatically if your finger slips off. It also works without a flash, for example in Safari on iPhone, as long as you are somewhere bright. If you would rather not use the camera, count the pulse at your wrist between two beeps over 10, 15, 30 or 60 seconds and convert it to a per-minute rate (with the error of the 15-second × 4 method shown), or tap a button in time with each beat. Results are compared with typical resting heart rate ranges for infants, toddlers, school-age children and adults, and can be logged as “just woke up”, “sitting at rest” or “after exercise”. From your age and resting heart rate it also works out your maximum heart rate (220 − age, or Tanaka's 208 − 0.7 × age) and heart rate reserve, and lists your Karvonen target heart rate and five training zones (such as zone 2 for fat burning), including how many beats to expect in a 10-second count during exercise.

Measure by placing a finger on your phone camera

The amount of blood in your fingertip changes slightly with every beat, making the red image the camera sees flicker. Your heart rate is worked out from the rhythm of that flicker.

bpm

Press “Start measuring” to turn on the camera

Measuring time

Tips for a good reading

Phones use the rear camera. If the flash is next to the lens, cover both with one finger.
Pressing hard restricts blood flow and makes the wave smaller. Touch the lens only lightly.
On devices where the flash cannot be turned on (such as Safari on iPhone), measure somewhere bright so light from a window or lamp shines through your finger.
Cold hands weaken the wave. Warm your hands first, then measure sitting down with your elbow on a table.
With the flash on for a long time the area around the lens can get hot. Lift your finger if it feels hot.

This tool is not a medical device. The values shown are estimates and cannot be used to diagnose illness. If you have chest pain, shortness of breath, dizziness or a feeling of skipped beats, see a doctor.

The camera image is only used on your device to calculate brightness and is never saved or sent. Your log is stored only in this browser on this device.

ABOUT

About Heart Rate Monitor | Measure Your Pulse by Placing a Finger on Your Phone Camera, a 15-Second × 4 Pulse Count Timer and Tap Counter, Karvonen Target Heart Rate and Training Zones, and Resting Heart Rate Ranges by Age with a Log

This heart rate monitor measures your pulse (beats per minute) in 15–60 seconds when you gently cover your phone's rear camera lens and flash with a fingertip. It reads the tiny darkening of the red image with every heartbeat (photoplethysmography, PPG), and shows the pulse waveform and signal quality. You can also count your wrist pulse with a timer or tap along, and calculate your Karvonen target heart rate and five heart rate zones from your age and resting heart rate.

How to use Heart Rate Monitor | Measure Your Pulse by Placing a Finger on Your Phone Camera, a 15-Second × 4 Pulse Count Timer and Tap Counter, Karvonen Target Heart Rate and Training Zones, and Resting Heart Rate Ranges by Age with a Log

1On the “Camera” tab, choose how long to measure (15, 30 or 60 seconds), press “Start measuring” and allow camera access
2Lightly cover your phone's rear camera lens and flash with the pad of your index finger (on a computer, cover the built-in camera)
3When the circle turns red and it says it is measuring, rest your elbow on a table and keep still. If your finger slips off, it restarts automatically
4When it finishes, check the heart rate and signal quality, choose when you measured (just woke up, sitting at rest, after exercise) and press “Save this result”
5Without the camera, use the “By hand” tab: count your wrist pulse between the two beeps and enter the number, or tap the button with each beat
6On the “Heart rate zones” tab, enter your age and resting heart rate and choose a maximum heart rate formula to see your Karvonen target heart rate and the beats per 10 seconds

Great for

Check your pulse right now with just your phone when you have no smartwatch or blood pressure monitor
Log your resting heart rate every morning on waking to notice lack of sleep, fatigue or getting ill
Practise the 15-seconds-times-4 pulse count in PE, nursing or care-work training
Work out your zone 2 (fat-burning) heart rate for jogging or walking from your own resting heart rate
Count your pulse for 10 seconds during exercise to see whether you are inside your target range
Roughly check whether a child's heart rate is within the typical range for their age
Try a camera-based heart rate monitor in the browser without installing an app

Good to know

The camera method uses photoplethysmography (PPG), the same principle as the optical heart rate sensor in a smartwatch. With each heartbeat the blood in the capillaries of your fingertip increases, absorbing more light, so the image gets slightly darker. The tool takes the average brightness of the centre of the image (whichever of red or green has the clearer rhythm), resamples it at 30 points per second and subtracts a 1.5-second moving average to remove slow drift before calculating.
The heart rate is found in two ways: the strongest rhythm between 40 and 200 bpm (Fourier transform) and the spacing between peaks of the wave. When the two agree within 3 bpm the average peak spacing is used; otherwise the rhythm value is shown. Because some wave shapes can produce a rhythm at double the true rate, it picks half that value if it is also strong enough.
Signal quality (good, fair, weak) is based on how much of the total signal belongs to the heartbeat rhythm (and its second harmonic) and how evenly spaced the beats are. Do not trust a reading marked “weak” — reposition your finger and measure again.
The flash (torch) turns on automatically in browsers such as Chrome on Android. Safari on iPhone cannot turn on the flash from a web page, so measure somewhere bright, letting light from a window or lamp shine through your finger.
The per-minute rate when counting by hand is “beats counted × 60 ÷ seconds”. Miscounting by one beat shifts the result by 6 bpm for 10 seconds, 4 bpm for 15 seconds and 2 bpm for 30 seconds. If your pulse is irregular, count for a full 60 seconds.
Typical resting heart rates are shown as 60–100 bpm for adults (13 and over), 70–120 for school-age children (6–12), 80–140 for toddlers (1–5) and 100–160 for infants (under 1). Endurance athletes often have resting rates in the 40s or 50s. These ranges cannot be used to diagnose illness.
“220 − age” is the most widely used formula for maximum heart rate and tends to underestimate it in older people. “208 − 0.7 × age” is from Tanaka et al. (2001) and “207 − 0.7 × age” from Gellish et al. (2007). If you have a value actually measured in an exercise test, that is the most accurate.
The Karvonen target heart rate is “(maximum heart rate − resting heart rate) × intensity + resting heart rate”. The part in brackets is called the heart rate reserve (HRR). Switching to “% of maximum heart rate” uses maximum heart rate × intensity, without your resting heart rate.
RMSSD (the root mean square of successive differences between beat intervals) is one measure of heart rate variability (HRV). One camera frame lasts about 33 ms, so the value is coarse and is only shown, for reference, when the signal is good.
This tool is not a medical device. The camera image is only used on your device to calculate brightness and is never saved or sent anywhere. Settings and the log are stored only in this browser on this device.

Questions this tool answers

Use Heart Rate Monitor | Measure Your Pulse by Placing a Finger on Your Phone Camera, a 15-Second × 4 Pulse Count Timer and Tap Counter, Karvonen Target Heart Rate and Training Zones, and Resting Heart Rate Ranges by Age with a Log for searches like these:

Measure my heart rate by putting a finger on my phone camera
Check my pulse in the browser without installing an app
Count my pulse for 15 seconds and multiply by 4 with a timer
Find the average and normal resting heart rate by age
Calculate my target heart rate with the Karvonen formula
Work out my fat-burning zone 2 heart rate from my resting heart rate
Compare 220 − age with 208 − 0.7 × age for maximum heart rate
How many beats in 10 seconds keeps me in my target zone during exercise

FAQ

Can a phone camera really measure heart rate?: Yes. When you cover the camera lens and flash with a fingertip, the amount of blood in your finger changes with each heartbeat and the brightness of the red image flickers very slightly. This signal (photoplethysmography, PPG) is the same principle used by smartwatch heart rate sensors, and if you stay still with your finger steady, the result is close to a pulse counted at the wrist. Pressing too hard, cold hands or movement weaken the signal and make the reading less reliable.
Does it work on iPhone? The flash does not turn on.: Yes. Safari on iPhone does not let web pages turn on the flash, so it measures without it. In a bright room or by a window, cover the rear camera lens with the pad of your finger so that light shines through your finger and the circle on screen looks red. In a dark place the signal becomes weak; use the “By hand” tab instead.
Is counting your pulse for 15 seconds and multiplying by 4 accurate?: It is good enough for an everyday resting check. However, miscounting by one beat changes the result by 4 bpm, and the error grows if your pulse is irregular. When accuracy matters or your heart seems to skip beats, count for 60 seconds. Right after exercise your pulse starts falling quickly, so counting for 10 seconds and multiplying by 6 is common.
What is a normal resting heart rate?: For adults, 60–100 beats per minute is the usual range. Children are faster: about 70–120 at school age, 80–140 for toddlers and 100–160 for infants. People who do endurance training, such as runners, may be in the 40s or 50s. For comparable day-to-day numbers, measure after waking and using the toilet, once you have sat quietly for 1–2 minutes.
How do I calculate my target heart rate with the Karvonen formula?: Use “(maximum heart rate − resting heart rate) × intensity + resting heart rate”. For example, at 40 years old with a resting heart rate of 65 bpm, maximum heart rate is 220 − 40 = 180 and heart rate reserve is 180 − 65 = 115, so the target at 60% intensity is 115 × 0.6 + 65 = 134 bpm. Enter your age and resting heart rate on the “Heart rate zones” tab to list all five zones.
What heart rate is best for burning fat (zone 2)?: Zone 2 is generally 60–70% intensity by the Karvonen method (around 70% of maximum heart rate) — an effort you can keep up while holding a conversation, at which a larger share of energy comes from fat. For a 40-year-old with a resting rate of 65 bpm it is about 134–146 bpm. Higher intensities use a larger share of carbohydrate but burn more calories overall, so choose according to your goal.
What should I do if the reading looks wrong?: If the signal quality says “weak”, lightly reposition your finger, rest your elbow on a table and keep your hand still, then measure again. Pressing hard restricts blood flow and makes the wave smaller. Warm your hands first if they are cold. If it still does not match, compare it with your wrist pulse on the “By hand” tab.
Is the camera image sent anywhere?: No. The image is only used on your device to work out the average brightness of each frame; it is never saved as a picture or sent to a server. The log is stored only in this browser (localStorage).

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