Biorhythm Calculator

Biorhythm theory proposes that human life follows three fixed sine-wave cycles starting from birth: Physical (23 days), Emotional (28 days), and Intellectual (33 days). Each cycle alternates between positive (high) and negative (low) phases. The theory suggests these cycles influence your physical strength, emotional mood, and mental sharpness, respectively.

Each biorhythm is calculated as sin(2 * pi * days_alive / period), where days_alive is the number of days since birth and period is 23 (physical), 28 (emotional), or 33 (intellectual). The sine function produces a value between -1 (low) and +1 (high). This value is often displayed as a percentage from -100% to +100%.

No. Biorhythm theory has not been validated by scientific research. Multiple controlled studies have found no correlation between biorhythm predictions and actual performance in sports, academics, accident rates, or other measurable outcomes. The scientific consensus is that biorhythms are pseudoscience. This calculator is for entertainment and curiosity only.

Critical days occur when a biorhythm cycle crosses zero (transitions from positive to negative or vice versa). Biorhythm theory suggests these days are periods of instability or unpredictability in that aspect. A double critical day (two cycles crossing zero) or triple critical day (all three crossing zero) is considered especially significant, though scientific studies have not validated these claims.

No. Studies conducted in the 1970s and 1980s tested biorhythm predictions against industrial accidents, athletic performance, and academic test scores. None found a statistically significant correlation. Biorhythms cannot reliably predict when you will perform well or poorly, or when accidents are more likely to occur.

Biorhythm theory assumes that all three cycles begin at zero on the day of birth and continue oscillating at their fixed periods throughout life. This is an arbitrary assumption with no biological or scientific basis. There is no evidence that birth date determines any cyclical patterns in human physiology or psychology.

The Physical cycle lasts 23 days, the Emotional cycle 28 days, and the Intellectual cycle 33 days. These periods were chosen by the early proponents of the theory based on anecdotal observations. The three cycles align (all cross zero on the same day) approximately every 21,252 days (about 58 years), which is the least common multiple of 23, 28, and 33.

No. All calculations happen entirely in your browser using JavaScript. Your birth date is never sent to any server, stored in any database, or logged in any way. You can use this tool completely offline after the page loads.

Wilhelm Fliess chose 28 days because it matches the average length of the menstrual cycle. However, this does not mean the emotional biorhythm is related to menstruation. Fliess believed 28-day cycles applied to all humans regardless of sex, which has no scientific support. The choice was based on numerology rather than biology.

No. Circadian rhythms are real, scientifically validated 24-hour biological cycles that regulate sleep, hormone release, body temperature, and other physiological processes. They are influenced by light-dark cycles and are governed by internal biological clocks. Biorhythms, in contrast, are longer fixed cycles (23, 28, 33 days) that have no scientific evidence and are considered pseudoscience.

Biorhythm theory proposes that human life follows three fixed cycles starting from birth: Physical (23 days), Emotional (28 days), and Intellectual (33 days). Each cycle oscillates between positive and negative phases as a sine wave. When a cycle is positive, that aspect is supposedly at its peak; when negative, it is at a low point.

Each biorhythm is calculated as sin(2 * pi * days_alive / period). The physical cycle has a 23-day period, emotional 28 days, and intellectual 33 days. The result ranges from -1 (low) to +1 (high). Critical days occur when a cycle crosses zero, supposedly indicating instability.

No, biorhythm theory has not been validated by scientific research. Multiple studies have found no correlation between biorhythm predictions and actual performance or well-being. It remains a pseudoscience, though many people find it entertaining as a curiosity.

Critical days occur when a biorhythm cycle crosses zero (transitions from positive to negative or vice versa). Biorhythm theory suggests these transition days are periods of instability or unpredictability in that area. Double critical days (two cycles crossing zero) are considered especially significant in the theory.