Biorhythm Calculator – Physical, Emotional & Intellectual Cycles (Chart)

How to use

Enter your date of birth.
Read today's three percentages.
Scan the 30-day chart for critical days.

About this tool

Biorhythm theory proposes three fixed cycles that run from the moment of birth: a 23-day physical cycle, a 28-day emotional cycle and a 33-day intellectual cycle. Each is a sine wave, so any given day sits somewhere between the peak and the trough, and the days where a curve crosses zero are traditionally called critical days. This tool computes the exact phase for today and draws the next 30 days so you can see the pattern rather than just a number. The theory dates from the early 1900s and is not supported by scientific evidence — it is presented here as the classic calculation, done properly.

FAQ

Is my birth date stored?

No — the calculation is local and nothing is saved.

What do the percentages mean?

The position on each sine curve: +100% is the peak, 0% is the critical crossing, −100% is the trough.

What is a critical day?

The day a cycle crosses zero, traditionally considered a transition point.

Is biorhythm scientific?

No. It is an early twentieth-century idea without scientific support — treat the chart as a curiosity.

Why 23, 28 and 33 days?

Those are the cycle lengths the original theory specified.

Can I check a past date?

Yes — change the target date field to any date.

Questions people ask about Biorhythm Calculator

Collected from live search results on 31 Aug 2026 (search-engine "people also ask" boxes plus the questions published on ranking pages).

how is biorhythm calculator