Flow: An Experimental Focus + Relaxation Index
Estimated from a single camera (PPG) reading — an educational estimate, not a medical measurement. State labels (Flow, Focus, Alarm…) are rough, experimental patterns, not emotion detection.
What this number is
Flow here is an experimental index that tries to capture a combination people often describe during absorbed work: attention that holds steady while the body stays reasonably calm. The browser tool cannot read your attention or your mind. It only combines two of its other indices, Focus and Relaxation, which themselves come from your heart rate and the irregularity of your beat-to-beat intervals.
How this tool calculates it
Flow = 0.6 × Focus + 0.4 × Relaxation, limited to 0–100%. The tool works on a rolling 15-second window of fingertip video (about 30 frames per second), finds each pulse peak, keeps only beat-to-beat (RR) intervals between 400 and 1,500 ms that are within 22% of the median, and smooths the displayed numbers so they change gradually. Because Focus and Relaxation both rise when your heart rate is moderate and your rhythm is steady (low CSI), Flow rises in the same situations.
How to read it
Higher
Your pulse was moderate and your beat intervals were fairly even during the reading. That can accompany calm, engaged attention, but it can also simply mean you sat still with a clean signal.
Lower
Heart rate was higher, the rhythm looked more irregular, or both. Movement, finger pressure changes and poor lighting push it down too, because they add noise to the camera signal.
Important limits
This is an experimental heuristic built from a few camera-derived inputs. It is not a validated physiological measure, it is not emotion detection, and it is not a medical test. Treat it as a rough hint about the direction your signal is moving, not as a verdict about how you feel. The psychological state called "flow" is studied with questionnaires and task performance, and there is no accepted way to detect it from a 15-second fingertip reading.
What actually helps
Reduce interruptions
Close notifications and pick one task. Frequent switching is a reliable way to break concentration.
Slow breathing before deep work
A few minutes of slow, relaxed breathing often lowers heart rate a little and makes the rhythm steadier.
Sleep and breaks
Attention is easier to sustain when you are rested; short breaks every hour or so help too.
The ONDA app is a separate product: it focuses on pulse, breathing and, with an Apple Watch, coherence. It does not use the formulas on this page.
The ONDA Principle
Use Flow as a curiosity, not a score to chase: it goes up when your pulse is moderate and your rhythm is steady.
Ready to measure?
The ONDA app works with your iPhone camera, Apple Watch and Apple Health.