Research shows smartphone PPG is within 2–3 bpm of clinical-grade monitors at rest. Here's what affects your reading quality and how to get consistent results.
It is fair to be skeptical that a phone camera can measure your heart accurately. The technique is photoplethysmography (PPG): your fingertip over the lens, lit by the flash, reveals tiny colour changes with each pulse. This guide explains how accurate that really is, and the simple things that make a reading trustworthy.
The variation between heartbeats — your nervous system's report card.
Two metrics, one number. Why Pulse shows both — and which to watch.
Training-impulse: your weekly training load, in one chart.
Camera-based HR works best at rest. Sit quietly and press your fingertip firmly (but not too hard) against the rear camera. Motion artifacts are the #1 source of error.
Pulse Rate activates the camera flash to illuminate your fingertip capillaries. Avoid direct sunlight on the lens, which can saturate the sensor and introduce noise.
Cold fingers constrict capillaries and reduce PPG signal quality. Warm your hands for 1–2 minutes before measuring if you've been outside in cold weather.
The real power of camera HR is trend tracking. A single reading carries some margin of error; 30 daily readings reveal patterns that are meaningful for wellness logging.
The same chart that lives on your iPhone's Progress screen — rebuilt so you know what you're looking at.
Outstanding score. Your key heart metrics are above normal.
Most healthy adults fall within this range.
Not necessarily alarming — but worth monitoring.
If this persists, please consult a healthcare professional.
TRIMP = duration × intensity. A 60-minute easy run scores about 70 TRIMP. A 30-minute interval session scores 110. Pulse adds them up daily and tells you when your week is too light, just right, or about to overcook you.
For resting heart rate and RMSSD, a still 60-second iPhone photoplethysmography reading tracks within roughly ±3 ms of a chest-strap ECG. That is clinically acceptable for trend monitoring, though not a substitute for a medical device.
Movement, a loose fingertip, cold hands, or pressing too hard all add noise. Sitting still, keeping the finger steady over both lens and flash, and breathing normally for the full minute give the cleanest result.
PPG from a fingertip needs you to be still, so it is ideal for resting heart rate and morning HRV. For live heart rate during hard movement, a chest strap is the better tool.
Yes. Photoplethysmography is the same optical principle used in pulse oximeters and most wrist wearables; Pulse applies it through the iPhone camera and flash.
You've already got the hardware — your iPhone. Pulse does the rest.
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