Biorhythms
Biorhythms are three sine waves counted from your date of birth: physical with a period of 23 days, emotional with 28, and intellectual with 33. The calculator above shows where you are on each curve on the chosen day, draws a chart for two weeks before and after it, and names the nearest peaks, lows and critical days.
How it is calculated
The number of days lived is counted, and for each cycle the sine of the fraction of the period elapsed is taken. The value is expressed as a percentage from −100 to +100.
The upper half of the curve is a high, the lower half a low. Days when a curve crosses zero are called critical: the indicator is believed to be unstable on them. If two or three curves cross zero on the same day, tradition considers such days the most unlucky: the advice is not to rush and to double-check what you have done. Such a day does not mean danger, illness or misfortune.
No data about you other than your date of birth is needed for the calculation.
What the three curves mean
| Cycle | Period | Governs |
|---|---|---|
| Physical | 23 days | Stamina, strength, coordination |
| Emotional | 28 days | Mood, sensitivity, relationships |
| Intellectual | 33 days | Attention, memory, the ability to calculate |
Sometimes a fourth cycle is added, the intuitive one, with a period of 38 days, but it does not appear in every version and is not included in the calculation here.
An Honest Look at the Method
The theory of biorhythms was proposed at the turn of the 20th century by Wilhelm Fliess and Hermann Swoboda, and it became popular in the 1970s. Since then it has been tested many times: on sports results, accidents, and industrial performance.
The results of these tests are negative: studies find no link between biorhythm phase and actual achievements or incidents. The scientific community classifies biorhythms as a pseudoscientific theory.
We keep this calculation on the site as entertainment and as a handy chart, not as a tool for planning your health or work.
Frequently asked questions
Can I use biorhythms to choose a day for an exam or surgery?
No. For surgery there is a doctor; for an exam, preparation.
Why do two people of the same age have different charts?
The cycles are counted from the date of birth, and a difference of even one day shifts all three curves.
What is biorhythm compatibility?
A comparison of two people's curves: the more closely the phases match, the higher the “compatibility” on this scale. It is a consequence of the difference in birth dates, not a property of the relationship.