Biorhythm calculator
Biorhythm theory assumes three cycles running from the day you were born: a 23-day physical one, a 28-day emotional one and a 33-day intellectual one. The calculator gives your position in each cycle on the chosen day, as a percentage between minus and plus one hundred.
Biorhythm is a nineteenth-century curiosity, not a medical tool: the studies that tested it found no link between the cycles and performance or health. Treat the result as an arithmetic game, not as advice.
Frequently asked questions
What is a critical day?
The day a cycle crosses zero and changes sign. In the original theory that is where instability peaks, not at the high or the low.
Why 23, 28 and 33 days exactly?
They are the numbers Wilhelm Fliess proposed in the late 1800s, kept by everyone who carried the idea forward. They have no physiological basis.
Can I calculate it for someone else?
Yes, all it needs is their birth date. Nothing is sent anywhere; the whole calculation happens in your browser.