Two dates of birth, the relationship type, and a reading of your compatibility today.
Privacy first. Mathematical calculation on biological cycles of 23, 28 and 33 days.
The test compares the three biorhythm cycles of two people across a 30-day window and returns a score from 0 to 100. All it needs is the two birth dates and the relationship type. No zodiac signs involved: these are cycles calculated from each person’s day of birth.
| Axis | Cycle | Where you notice it |
|---|---|---|
| Physical | 23 days | Energy and the rhythm of days spent together |
| Emotional | 28 days | Patience with each other and how you react |
| Intellectual | 33 days | Communication and shared decisions |
Two couples with the same overall score can be living opposite situations. The useful information sits in the gap between axes, not in the total.
Means you understand each other on that axis with little effort. It does not remove conflict or replace talking: it is a head start, and head starts can be wasted.
Tells you your rhythms run independently there, so it takes more attention. It does not say you are incompatible: it says where you are spending more energy.
How to read a result, with examples
Search for a couple compatibility test and you will find three very different things. They are worth telling apart.
A biorhythm is a calculation. You count the days since the birth date, and from there three fixed-length cycles run: 23 days for the physical, 28 for the emotional, 33 for the intellectual. They are the same for everyone and do not shift with the opinion of whoever reads them. The same two dates give the same result today, tomorrow and in ten years, and anyone can redo the arithmetic and land on the same numbers. No birth time, no birthplace, no belief required: just a date.
Behind it sits more than a century of work on biological periodicity, from Wilhelm Fliess in 1897 through Hermann Swoboda to present-day chronobiology. That the body runs on cycles is not a romantic hypothesis: it is the field that won the 2017 Nobel Prize in Medicine for the study of internal biological clocks. The three-cycle method is the classic formulation of that insight, and it is what we calculate here.
Couple astrology starts somewhere else: the position of the planets at birth. It needs the exact hour, it shifts with the tradition you follow, and it works if you believe in it. A legitimate choice, but a different one. The full comparison with astrology apps.
Love calculators count the letters in your names. Change a nickname and the percentage changes. They are a game, and nobody claims otherwise.
We sit in the first category: numbers you can check, not a verdict to accept.
The structural comparison between two dates never changes: the cycles are periodic, so the score on each axis stays put. When a low score is not a problem.
What moves every day is the snapshot: where your six cycles sit today, and which days next week find you in step or out of it. Worth a look before a decision that involves you both, a trip, or a conversation you keep postponing.
Running it daily hoping for a different number, on the other hand, gets you nowhere: that is the number.
Do we need the time of birth?
No. The two birth dates are enough.
What is the calculation based on?
Three fixed-length cycles starting on the day you were born: 23, 28 and 33 days. It is arithmetic, not interpretation: same dates, same result, every time, for anyone who redoes the sum. The model comes out of late-nineteenth-century work on biological periodicity and runs through a century of research into today’s chronobiology.
Is a biorhythm the same thing as a horoscope?
No, and the difference is one of method. A horoscope interprets planetary positions and needs your time of birth. A biorhythm counts the days since birth and applies three fixed periods that are the same for everyone. One asks you to believe; the other you can check with a calendar.
What counts as a good score?
Above 70 is a marked affinity, 40 to 70 is the common band, below 40 means rhythms running on their own. But the total matters less than the shape: a 55 with three balanced axes tells a different story from a 55 built on one very high axis and two low ones.
Is the first result free?
Yes, and it needs no account. The in-depth reading for each axis sits in the Premium plan.
Do I need to give an email to see the result?
No. The first result is free and asks for neither an account nor an email address.
Is it only for romantic couples?
No. Picking the relationship type (partner, friend, family, coworker, acquaintance) changes how the axes are weighted: with a coworker the intellectual one carries most of it.
Why does the result change when I change the relationship type?
Because the weight of each axis changes. With a coworker intellectual rapport carries most of it; with a partner it is the balance across all three. The dates stay the same, the lens changes.
Does it work for long-distance couples?
Yes. The calculation starts from birth dates, not from where you are. If anything the day-by-day reading is more useful when you see each other rarely, because it helps you pick when to talk.
Does the result expire?
No. The cycles are periodic, so the structural comparison between two dates holds over time. Only the day-by-day picture moves.
Does a low score mean we should break up?
No. No test can tell you what to do with your relationship. It shows which axis your rhythms diverge on, so where more awareness helps.
The score is not a verdict on your relationship, and it does not try to be. It is a map of rhythms: it tells you which axes you move along together with ease and which ones need more attention and more words.
What it hands back is language for something you already live, namely that some weeks run smoothly and others do not. The couples who use it well treat it as the start of a conversation they had been putting off, not as a sentence. What a compatibility test is not meant for.
We do the arithmetic, in thirty seconds and for free. You supply the confirmation, by recognising yourselves in it or not.
The biorhythm method grows out of more than a century of work on biological periodicity, from Wilhelm Fliess onward, a tradition that continues today in chronobiology. We present it for what it is: a verifiable calculation meant for self-observation, not a diagnosis and not a forecast about the future of a relationship. The historical sources, including the critical ones.