Biorhythm Calculator — Your Free Daily Biorhythm Chart
Enter a date of birth and this free biorhythm calculator plots your biorhythm chart across eight cycles — physical, emotional and intellectual plus five supporting rhythms — with a plain-English reading for any day. Everything is calculated on your device.
Want more? Check biorhythm compatibility between two people, find your Primal Zodiac sign, work out your Life Path number or generate a Human Design chart.
Works offline when installed on a supported Android browser.
Your details
Nothing you enter leaves this device.
Add a date of birth above to generate the chart and the daily analysis.
Biorhythm compatibility — compare two people
Save at least two profiles to compare their rhythms here.
Add profiles in My List, then come back to compare any two of them on a chosen date.
Exact data and methodology
Dates are normalised to whole UTC calendar days, so daylight-saving changes cannot shift a result. Each rhythm value is R(D) = 100 × sin(2πD ÷ P), where D is the number of days lived and P is the cycle period in days.
Direction compares today with tomorrow: more than +3 is rising, less than -3 is falling, and anything between is near a turning point. Phases run from Peak (+85 or above) to Trough (-85 or below).
The daily pattern is chosen from eight named configurations in a fixed priority order, using only the three core rhythms plus a transition count across all eight. Pair relevance is |A| + |B| + 0.35 × |A − B| plus a fixed bonus for the matching pair type.
No artificial intelligence, profiling, probability, astrology or external data is used at any point.
Everything is stored in your browser's local storage under a single key. There is no account, no server and no analytics profile attached to your dates.
Clearing your browser data or the site's storage removes it permanently.
Biorhythm Compass 4.25.0, using Compass Rhythm Synthesis — CRS Algorithm v1.0. When a new version is deployed the app offers an update banner and keeps your saved people, couples and settings.
Biorhythm calculator — common questions
What is a biorhythm?
A biorhythm is a repeating cycle counted from your date of birth. Each cycle rises to a high, falls to a low and crosses zero on a fixed rhythm, and a biorhythm chart plots those curves side by side as a prompt for reflection.
How does a biorhythm calculator work?
It counts the number of days since your date of birth and places that day inside each cycle: 23 days for the physical cycle, 28 for the emotional cycle and 33 for the intellectual cycle, plus five supporting cycles. Biorhythm Compass does all of this in your browser, so no date of birth is uploaded.
Are biorhythms scientific?
No. Biorhythm theory is not scientifically established. The chart is offered for entertainment and personal reflection only, and it is not medical, psychological or predictive advice.
Can I check biorhythm compatibility between two people?
Yes. Save two profiles, pair them, and the free biorhythm compatibility view overlays both sets of cycles on a chosen date with a simple alignment score.
Guides
Plain-English articles on every tool here, with worked examples and diagrams.
Biorhythm calculator
Biorhythm Calculator Guide — Read Your Chart
A biorhythm calculator counts the days between your date of birth and a chosen date, then places that day inside a set of repeating cycles — 23 days for physical, 28 for emotional and 33 for intellectual, plus five supporting cycles. The result is a chart of smooth waves between +100% and -100%. It is a reflection tool, not a forecast: the value of the chart is the questions it makes you ask about your own week.
7 min read
Biorhythm compatibility
Biorhythm Compatibility — Compare Two Charts
Biorhythm compatibility compares where two people sit in the same cycle on the same day. When both physical lines are high, shared effort feels easy; when one is high and the other low, the pair is naturally out of step for that kind of activity. The score is a percentage of phase similarity across the cycles — a description of timing, not a verdict on a relationship.
6 min read
Primal Zodiac
Primal Zodiac Guide — Your Combined Sign
The Primal Zodiac combines your Western star sign, which comes from the month and day you were born, with your Chinese zodiac animal, which comes from the lunar year. Twelve signs multiplied by twelve animals give 144 combinations, each with its own named creature and profile — a much narrower description than a star sign alone.
6 min read