Excitement: An Experimental Arousal 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
Excitement here is an experimental index of general physiological arousal. It rises with heart rate above 60 bpm and, a little, with breathing rate. It cannot tell positive excitement apart from nervousness, physical effort or caffeine, because the body shows all of these with a faster pulse.
How this tool calculates it
Excitement = 1.5 × (heart rate − 60) + 0.5 × breathing rate, limited to 0–100%. Heart rate is 60,000 divided by the average RR interval; breathing rate is estimated from slow changes in the pulse signal and counts as 0 when the tool cannot find a clear rhythm. 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.
How to read it
Higher
Your heart rate was well above 60 bpm. At 80 bpm and 15 breaths per minute, for example, the index is about 38%; at 100 bpm it is about 68%.
Lower
Your pulse was close to 60 bpm or below. Many relaxed, fit adults sit here at rest.
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. In practice this index is mostly a rescaled heart rate, so it carries the same caveats as heart rate itself.
What actually helps
Name the cause
If the number is high, ask what just happened: movement, coffee, a stressful message, or anticipation. The body response is similar in each case.
Slow exhale to settle
If you want to calm down, a few breaths with a longer exhale than inhale tend to lower heart rate over a minute or two.
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
Excitement is essentially "how far above 60 bpm is your pulse right now", expressed as a percentage.
Ready to measure?
The ONDA app works with your iPhone camera, Apple Watch and Apple Health.