∿︎ Biorhythm · Calculator
Biorhythm Calculator
See your physical, emotional and intellectual cycles for today and the days ahead. Enter your birth date — and optionally a date to check — and the calculator does the rest, right in your browser.
Your dates never leave your browser. Nothing is stored or sent.
Good to know — biorhythm theory has no scientific or medical backing. The cycles are entertainment and light self-reflection only; never use them as health advice or to make important decisions.
How the biorhythm calculator works
This biorhythm calculator starts from the idea that three cycles begin on the day you are born and repeat at a steady pace ever after — a physical cycle of 23 days, an emotional cycle of 28 days and an intellectual cycle of 33 days. Each is drawn as a sine wave swinging between a high of +100% and a low of −100%.
To find where you sit today, the calculator counts the exact number of days you have lived and places that figure on each wave. You get a reading for your physical, emotional and intellectual state right now, plus a short preview of the days ahead so you can see which cycles are rising and which are dipping.
Reading your cycles
A high phase, above +50%, is said to bring extra energy in that area; a low phase, below −50%, is read as a time to rest and recharge. When a cycle crosses the zero line it is called a "critical day" — traditionally seen as a wobblier, less predictable moment. Remember that biorhythm is a pseudoscience: enjoy it as a curiosity, not a forecast. Enter your birth date above to begin.
Frequently asked questions
What is a biorhythm?
Biorhythm theory suggests three cycles begin at birth and repeat steadily — a physical cycle of 23 days, an emotional cycle of 28 days and an intellectual cycle of 33 days — each drawn as a sine wave that rises and falls over time.
How is it calculated?
The calculator counts the number of days you have been alive and plugs that into the sine formula for each cycle length. The result is a percentage from −100% to +100% for your physical, emotional and intellectual state on any given day.
What do high, low and critical days mean?
A high phase (above +50%) is said to bring more energy in that area, a low phase (below −50%) invites rest, and a "critical day" is when a cycle crosses zero — traditionally seen as a wobblier, less predictable day.
Is biorhythm scientifically proven?
No. Biorhythm theory is regarded as a pseudoscience with no medical evidence behind it. Treat the results as entertainment and a bit of self-reflection, never as health advice or a basis for important decisions.