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A biorhythm is a hypothetical cyclic pattern of alterations in physiology, emotions, and/or intellect. "Bio" pertains to life and "rhythm" pertains to the flow with regular movement.

Biorhythm Chart

Basic theory[]

The theory of biorhythms claims that one's life is affected by rhythmic biological cycles, and seeks to make predictions regarding these cycles and the personal ease of carrying out tasks related to the cycles. These inherent rhythms are said to control or initiate various biological processes and are classically composed of three cyclic rhythms that are said to govern human behaviour and demonstrate innate periodicity in natural physiological change: the physical, the emotional, and the intellectual (or mental) cycles. Others claim there are additional rhythms, some of which may be combinations of the three primary cycles. Some proponents think that biorhythms may be potentially related to bioelectricity and its interactions in the body.

Basic Rhythm Details:

  • Physical cycle (23 days; Circavigintan)
    • coordination
    • strength
    • well-being
  • Emotional cycle (28 days; Circatrigintan)
    • creativity
    • sensitivity
    • mood
    • perception
    • awareness
  • Intellectual cycle (33 days; Circatrigintan)
    • alertness
    • analytical functioning
    • logical analysis
    • memory or recall
    • communication

Basic rhythms follow certain facets of physiological cycles, though they may include others, and the details may vary depending on the source. The three classical cycles of biorhythms are endogenous infradian rhythms. The theory's basis lies in physiological and emotional cycles. They are often represented graphically as either symmetric or asymmetric waveforms, though most theories rely on symmetric forms. The most commonly used form is the sinusoidal waveform, which is thought to be a plausible representation of a bioelectric activity cycle. Due to this sinusoidal nature, the cyclical flow of bioelectric activity undergoes periodic reverses in direction. Each cycle oscillates between a positive phase [0%..100%] and a negative phase [-100%..0%], during which bioelectric activity strengthens and weakens. The waveforms start, in most theories, at the neutral baseline (0%) at the time of birth of each individual. Each day that the waveform again crosses this baseline is dubbed a critical day, which means that tasks in the domain of the cycle are supposed to be far more difficult to carry out successfully than on other non-critical days. The purpose of mapping the biorhythmic cycles is to enable the calculation of critical days for performing or avoiding various activities.

The classical definition (derivatives of the original theory exist) states that one's birth is an unfavorable circumstantial event, as is the day about 58 years later when the three cycles are again synchronised at their minimum values. According to the classical definition, the theory is assumed to apply only to humans. In the classical theory, the value of each cycle can be calculated at any given time in the life of an individual, and there are web sites that do exactly that.

Related terminology[]

Biorhythmics is either a protoscientific branch or a pseudoscience, depending on opinion, that studies biorhythms or deal with biorhythms. Biorhythmic study focuses on physiological, emotional, and intellectual processes and its forecasting. Biorhythm phenomena are observable human conditions which can be detailed and explained by biorhythmics. These conditions are bound by the variables that exist in the body. Certain facets of biorhythmics are likened by proponents to concepts found in weather forecasting (commonly known as meteorology).
Chronobiology is a branch of biology that studies rhythms in living beings. Unlike biorhythm, its status as a science is unquestioned.

Biological rhythm cycles[]

Ultradian are the biological rhythms having extremely short cycles (lasting less than 24 hours).
Circadian are the biological rhythms having a period of 24 hours (lasting a day).
Infradian are biological rhythms composed of long-term cycles (lasting several days).
Exogenous are cycles influenced by external factors.
Endogenous are cycles not influenced by external changes.
Circatrigintan are cycles that recur every month (around 25-35 days).
Circavigintan are cycles that recur triweekly (around 17-23 days).
Circadiseptan are cyles that occur biweeklly (around 12-17 days).
Circannual are cycles that recur every year (around 365 days).


In the workplace, railroads and airlines have experimented the most with biorhythms. A pilot describes the Japanese and American attitudes towards biorhythms. [1] He acknowledges, researching his pilot logbook, that his greatest errors of judgment occurred during critical days, but concludes that an awareness of one's critical days and paying extra attention is sufficient to ensure safety. A former United Airlines pilot and user of the Biorhythms for Windows[2] program confirms that United Airlines used biorhythms until the mid-1990s, while the Nippon Express air freight still used biorhythms.

Charting biorhythms for personal use was quite popular in the United States during the 1970s; many places (especially video arcades and amusement areas) had a biorhythm machine where you could enter your date of birth and get a current chart.


The classical theory originated at the turn of the 19th century, between 1897 and 1902, from observational research.

Dr. Hermann Swoboda (Professor of Psychology, University of Vienna), who was researching periodic variations in fevers, looked into the possibility of a rhythmic change in mood and health. He collected data on reaction to pain, outbreak of fevers, illnesses, asthma, heart attacks, and recurrent dreams. He concluded that there was a 23-day physical cycle and a 28-day emotional cycle.

Dr. Wilhelm Fliess (nose and throat specialist; reportedly a numerologist) was independently researching the occurrences of fevers, recurrent illnesses and deaths in his patients. He too came to the conclusion that there was a 23 and a 28-day rhythm. Fliess's theories were of great interest and importance to Sigmund Freud during his early work in developing his psychoanalytic concepts.

Alfred Teltscher (professor of engineering; University of Innsbruck, Austria) observed that his students' good days and bad days followed a rhythmic pattern of 33 days. Teltscher found that the brain's ability to absorb, mental ability, and alertness ran in 33 day cycles. In the 1920s, Dr. Rexford Hersey (psychologist; Pennsylvania, America) also reportedly made contributions to the classical theory.

These three biorhythms compose the classical theory. The classical theory has been studied, especially in Germany, Japan, and the United States, with conflicting results. Various modern derivatives exist of the classical theory.

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Proponents of biorhythmics call it an established interdisciplinary area of scientific endeavor, which is still speculative in many facets. Critics state that biorhythms are based upon only numerological associations and elementary math. Biorhythmics' plausibility is contested by various mathematicians, some biologists and other scientists.

Biorhythms have echoes of chronobiology, the study of circadian and other rhythms. Through medical research, doctors have found that there are periodicity and rhythms during a person's lifespan, although few doctors believe they correspond to those described as "biorhythms". Biochronometry has shown that rhythm and cycles such as the circadian (from the Latin circa diem; literally, "about a day") exist. These discoveries, among others, have shown that people are affected by physiological, emotional and intellectual rhythms (though the exact relationships to the biorhythm cycles are not precisely understood). Studies in this (some say, self-described) protoscience are still being done regarding the effects of biorhythm on the human condition.

The Biorhythm theory is often treated as falsely claiming scientific validity. Biorhythm critic responses range from opposing it as harmful through ignoring it to accepting it as entertainment. Some biorhythm critics raise one or more of the following criticisms for the various theories that fall under the category of Biorhythmics:

  • Arbitrary assumption of sinusoidal cycles,
  • Arbitrary assumption of a neutral baseline,
  • Arbitrary choice of the periods of 23, 28, and 33 days,
  • Assumption that the cycles are the same for everyone,
  • Assumption that the cycles are set to zero at the moment of birth,
  • Assumption that the cycle lengths are unchanging throughout one's life,
  • Reliance on anecdotes,
  • Arguments based on ignorance of number theory,
  • Basic mistakes in setup of tests of the hypothesis,
  • Inadequate quantitative generalizations of complex human behavior,
  • Non-precise formulations of existing theories,
  • Peer review failures of experimental data,
  • Replication failures, and
  • Some unscrupulous practitioners' resemblance to professional fortune-telling fraud artists


It is possible to calculate one's biorhythm using one's birthdate. These calculations will result in a graph showing three curves, each representing one of the three cycles. It is advised to do these calculations in a spreadsheet such as the well-known Excel, as they are quite complicated and numerous, especially if you want to calculate your personal cycles for an entire month or even an entire year. Please note that there are more accurate methods involving one's exact hour of birth (assuming the Biorhythm theory is correct).

Here is how to calculate your three cycles' flow:

1) Calculate the number of days that have passed since Jan. 1, 1900:

  • Take the current year and subtract 1900 (e.g. 2006 - 1900 = 106). This number is further referred to as the present year. Please note that if you wish to calculate the three cycles of a month in another year, you should work with that year and not the current one.
  • Now calculate the days between March, 1900 and the present day, called here the first number: multiply the number of the present year by 365. Add the result of multiplying the number representing the current month by 29.53. Add the result of dividing the number representing the present year by 4. Subtract the result of dividing the number representing the present year by 100. Add the current day, further referred to as the current day. The result of this long formula is called, as previously mentioned, the first number.

2) Calculate the number of days from Jan. 1, 1900 until your birthday:

  • Take your birth year and subtract 1900 (e.g. 1976 - 1900 = 76). This number is further referred to as your birth year.
  • Now calculate the days between March, 1900 and your birthday, called here the second number: multiply your birth year by 365. Add the result of multiplying the number representing your month of birth by 29.53. Add the result of dividingyour birth year by 4. Add the result of dividingyour birth year by 400. Subtract the result of dividing your birth year by 100. Add your day of birth, further referred to as your day of birth.

3) Calculate the days that have passed since your birth

  • Subtract the second number (days to birthday) from the first number (days to present day). The result is the number of days you have lived since birth (referred to here as days s.b..

4) We can finally calculate the status of every cycle for every day of the month.

  • For the physical cycle, multiply 2 with pi. Multiply this with the result of adding days s.b. to the current day of the month and subtracting 1. Divide this by 23. The sine of the result of that is the number representing the state of the physical cycle of whichever current day of the month you chose.
  • For the emotional cycle, do the same as for the physical cycle with the only difference being you should divide by 28 and not 23 like for the physical cycle.
  • For the intellectual cycle, do the same as for the physical cycle, with the only difference being you should divide by 33 and not 23 like for the physical cycle.

You now know what the status of every of the three cycles is for whichever day of whichever month you chose. Generally, a 1 (100%) means the status of that cycle is being at high level, whilst -1 (-100%) means that the status of that cycle is at a low level. 0 (0%) means that the status of that cycle is at an average level. When taking your results into account in the daily life, please keep in mind that the science dealing with Biorhythms is not (yet) an established science.

While the above method is correct, a simpler version exists, more suited towards computers and programming to speed up the process of calculating a persons biorhytms.

  • Calculate the number of days the person has been alive (including leap days)
  • Divide that number by the cycle length you require (23,28 or 33). This will give you the number of cycles the person has lived through so far.
  • Remove the integer leaving you with just a fraction (i.e 234.874 becomes 0.874). This is how far into the current cycle the person is.
  • Convert this number to degrees by multiplying it by 360
  • The sin of the number above is equivalent to that persons biorhythm for that particular day.
    • Please note, to calculate for a different day, just work out the number of days between birth and the date.
    • Some programming languages require the sin argument to be in radians rather than degrees, check beforehand.

Easiest of all, simply use the following:

  • Physical = sin(2πt/23)
  • Emotional = sin(2πt/28)
  • Intellectual = sin(2πt/33)

Where t = # of days since birth, and calculations are done in radian mode.


- Bioclock calculating device for human body  
- Apparatus for measuring the actual psychophysiological condition  
- Biorhythms analog computer-calendar  
- Apparatus and method of determining fertility status  
- Biorhythm computer  
- Electronic calculator for determining biorhythm data

See also[]

External links, references, and resources[]

Reference citations[]

  1. "A man named Joseph and we knew him not!; Interpretation of Biorhythms regarding Flight Operations". (ed. Antedotal evidence; pilot describes the Japanese and American attitudes towards biorhythms.)
  2. Valentas Daniunas, "Biorhythms for Windows; Biorhythms for Windows Pro". Halloran Software, 2005.


Research publications[]


  • Hines, T. M., "Comprehensive review of biorhythm theory". Psychology Department, Pace University, Pleasantville, NY. Psychol Rep. 1998 Aug;83(1):19-64. (ed. concluded that biorhythm theory is not valid.)
  • D'Andrea, V. J., D.R. Black, and N. G. Stayrook, "Relation of the Fliess-Swoboda Biorhythm Theory to suicide occurrence". J Nerv Ment Dis. 1984 Aug;172(8):490-4. (ed. concluded that there was a validity to biorhythm when the innovative methods of the study are put to use.)
  • Laxenaire M., and O. Laurent, "What is the current thinking on the biorhythm theory?". Ann Med Psychol (Paris). 1983 Apr;141(4):425-9. [French](ed. Biorhythm theory is disregarded by the medical world though it has achieved a bit of fame with the public)
  • Wolcott, J. H., R. R. McMeekin, R. E. Burgin, and R. E. Yanowitch, "Correlation of general aviation accidents with the biorhythm theory". Hum Factors. 1977 Jun;19(3):283-93.
  • Khalil, T. M., and C. N. Kurucz, "The influence of 'biorhythm' on accident occurrence and performance". Ergonomics. 1977 Jul;20(4):389-98.
  • "Biorhythm in gynecology--a renaissance of Fliess' theory of periodicity?". Arch Gynecol. 1979 20 July;228(1-4):642. [German]
  • Nijsten, M.W., and S. E.Willemsen, "Accidents a matter of chance? The significance of lunar phases and biorhythms in trauma patients". Ned Tijdschr Geneeskd. 1991 21 December;135(51):2421-4. [Dutch] (ed. 'critical' biorhythm days were not found to increase the number of accidents experienced by subjects.)

Chronobiology related[]

Other sources[]

Biorhythms sources[]

Chronobiology sources[]

Skeptic sources[]

  • Gardner, Martin. "Science: Good, Bad and Bogus", Fliess, Freud, and Biorhythm. . CH. 11. Prometheus Books, Buffalo, N.Y. 1981. ISBN 0-87975-573-3
  • Hines, Terence M., Reprinted from: Psychological Reports, August 1998, "A comprehensive review of biorhythm theory". Psychology Department, Pace University
  • Skeptic's Dictionary entry


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