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Biorhythm calculator

Calculate your biorhythm — physical, emotional & intellectual cycles.

Enter your birth date and see today's biorhythm. Three sine-wave cycles (23-day Physical, 28-day Emotional, 33-day Intellectual) computed mathematically — no data sent anywhere, calculation happens in your browser.

Input

Enter your birth date

How it works

The math behind biorhythm

Biorhythm theory (Wilhelm Fliess, 1890s) posits three sine-wave cycles that begin at birth:

  • Physical: 23-day cycle
  • Emotional: 28-day cycle
  • Intellectual: 33-day cycle

Formula: sin(2π × d / period) where d = days since birth.

Note: Biorhythm theory has no scientific backing. This tool computes the mathematics exactly but makes no claims about predictive validity.

Frequently asked questions

What is a biorhythm?
Biorhythm is a theory that three internal cycles (Physical 23-day, Emotional 28-day, Intellectual 33-day) start at birth and influence wellbeing. The calculation is pure sinusoidal math.
What is a critical day?
A critical day is when a cycle crosses the zero line (transitioning from positive to negative or vice versa). Biorhythm theory considers these days more variable.
Is biorhythm scientific?
No. Biorhythm theory lacks scientific evidence. The math is precise but the predictive claims are not supported by research. This tool is for curiosity, not medical or psychological guidance.
Does the calculation send my data anywhere?
No. All computation happens in your browser. We never receive or store your birth date.
Biorhythm
Enter birth date to begin