Biorhythm Compatibility Calculator

What is this?

A Biorhythm Compatibility Calculator compares two people's biorhythm cycles from their dates of birth. Biorhythm theory holds that cycles begin at birth and repeat for life - physical every 23 days, emotional every 28 and intellectual every 33, with intuitive, aesthetic, awareness and spiritual cycles sometimes added. The theory has no scientific support and results are for entertainment.

How to Use the Biorhythm Compatibility Calculator

Biorhythm theory holds that three cycles begin at birth and repeat for life: a physical cycle of 23 days, an emotional cycle of 28 days and an intellectual cycle of 33 days. Four longer cycles - intuitive, aesthetic, awareness and spiritual - are sometimes added.

Compatibility compares two people's cycles. Because every cycle starts at birth, the only thing separating two people is the gap between their birth dates. Cycles that rise and fall together score 100%; cycles exactly opposite score 0%.

Biorhythm theory has no scientific support. This calculator works out precisely what the theory predicts, and nothing more should be read into it.

1. Enter Both Birth Dates

Enter the date of birth for each person. Names are optional and only label the result. The time of day is not used - biorhythms are counted in whole days.

2. Choose Which Cycles Count

All seven cycles are scored, but only the ones you tick are averaged into the overall figure. The three classic cycles are selected by default.

3. Read the Overall Score

The headline figure is the mean of the cycles you selected, with a rating from very low to very high.

4. Compare Cycle by Cycle

The bars show each cycle separately. Two people can be strongly matched physically and poorly matched emotionally - the average alone hides that.

Key Formulas Used in the Calculator

Compatibility for One Cycle

$\text{Compatibility} = \left| \cos\left( \frac{\pi \times \text{Gap in Days}}{\text{Cycle Length}} \right) \right| \times 100$

Each cycle is a sine wave beginning at birth, so two people's waves differ only by the gap between their birth dates. The cosine of that phase difference, taken as an absolute value, gives 100% when the waves line up and 0% when they are exactly opposed.

The Cycle Lengths

Physical 23, Emotional 28, Intellectual 33, Intuitive 38, Aesthetic 43, Awareness 48, Spiritual 53

All are counted in days from birth. The first three are the original theory; the four longer cycles were added later.

Overall Score

$\text{Overall} = \operatorname{Mean}\left(\text{Selected Cycles}\right)$

Only the cycles you tick are averaged. Selecting all seven gives a different figure from the three classic cycles alone, which is why the selection is shown with the result.

What the Extremes Mean

$\text{Gap of } 0\,\text{days} = 100\%$

$\text{Gap of Half a Cycle} = 0\%$

Two people born on the same day are perfectly in phase on every cycle. Two born half a 28-day cycle apart - 14 days - are exactly opposite on the emotional cycle, scoring 0%.

Benefits

• Covers all seven biorhythm cycles, not just the classic three

• Lets you choose which cycles count towards the overall score

• Shows each cycle separately as well as the average

• Uses a formula derived from the cycles themselves, and states it

• Two people born on the same day correctly score 100% everywhere

• Shows the gap in days between the two birth dates

• Says plainly that the theory has no scientific support

When & Where to Use

• Comparing your cycles with a partner's for fun

• Checking compatibility with a friend or family member

• Seeing which cycles align and which clash

• Understanding how biorhythm compatibility is worked out

• Comparing several people against the same person

• Settling curiosity about a claim you have read

Who Should Use This Calculator

The Biorhythm Compatibility Calculator is for anyone curious about biorhythm theory and how its compatibility scores are produced. It is entertainment rather than guidance.

Tips to Get the Best Deal

Only the gap between birth dates matters, so the result never changes day to day

The average hides detail - look at the individual cycles

Selecting different cycles changes the overall figure

A low score on one cycle does not drag down the others

Two people born a year apart are not automatically compatible; 365 does not divide the cycles evenly

Treat any result as a curiosity, not a verdict

Pro Tips

• Only the gap between birth dates matters, so the result never changes day to day.

• The average hides detail - look at the individual cycles.

• Selecting different cycles changes the overall figure.

• Two people born on the same day score 100% on every cycle.

• Different sites use different formulas, so percentages vary between them.

• Biorhythm theory has no scientific support; treat any result as a curiosity.