Biorhythm Calculator
Plot your physical, emotional and intellectual biorhythms around any date on an interactive chart.
Result
Biorhythm theory, popular since the 1970s, models three sine-wave cycles that start at birth: a 23-day physical cycle, a 28-day emotional cycle and a 33-day intellectual cycle. Highs are read as peaks of energy, focus or mood, lows as recovery time, and the days when a curve crosses zero as 'critical days' of instability.
This calculator counts the exact number of days you have lived, evaluates each cycle for the chosen target date, and draws all three curves for two weeks before and after it, so you can see at a glance where each rhythm is heading.
Each cycle is shown as a percentage from -100 to +100 with a plain-language state: high phase, low phase, or a critical day near the zero crossing, together with what that traditionally means for the cycle in question.
The mathematics is simple and fully transparent — sine waves with fixed periods — and it all runs locally in your browser. Scientific studies have found no predictive power in biorhythms, so enjoy the chart as a curious lens on your calendar, not as medical advice.