Biorhythm Calculator

Biorhythm theory proposes that three biological cycles influence our daily life from birth: a 23-day physical cycle (strength, coordination), a 28-day emotional cycle (creativity, mood), and a 33-day intellectual cycle (concentration, analysis).

Enter your birth date in our calculator. It calculates the number of days since your birth and applies sine wave formulas for each cycle (23, 28, and 33 days). The chart shows your current position and 30-day forecast.

Critical days occur when a cycle crosses the zero line, transitioning between positive and negative phases. During critical days, that aspect of your life may be unstable. Physical critical days suggest caution with exercise, emotional ones affect mood stability.

No. The theory of fixed 23, 28 and 33-day cycles goes back to Wilhelm Fliess in the late 19th century, and the studies that reviewed it found no evidence that it predicts performance, accidents or mood. We say so plainly because we’d rather you use the chart for what it is: an entertaining way to look at your rhythms and an excuse to pay attention to them, not a diagnosis or medical advice.

Not inside this calculator yet: for now it charts a single date of birth. In the meantime you can calculate yours, note the three percentages for the day, reload with the other date and compare which of the three cycles line up high and which line up low. Comparing two people on the same chart is on the to-do list.