"Bio" means life and "rhythm" means flowing with a regular movement. The principle behind biorhythms is that our lives are affected by three primary cycles: Physical, Emotional, and Intellectual plus a fourth, the Intuitional. These cycles start at a middle point when we are born and then rise and fall at different rates over our lifetimes. Because biorhythms are flowing at different speeds, they will not all meet at that same birth point again, until we are 58 years and 66 days old.

When a particular Biorhythm Calculator shows the cycle at a high point, things we relate to that biorhythm cycle are more successful - the reverse is true during the low points of a cycle. Many people report an improvement in the quality of their lives by monitoring their biorhythms and acting in accordance with them. There is no good or bad associated with these ups or downs. It is more like the vision of Yin and Yang, the Chinese symbols of the harmony of opposites: receptive and expressive, summer and winter. There is no way to avoid these swings, and we can use them to our advantage, like the surfer who sees the wave coming and catches it at just the right moment. If you think of rest and activity or regenerating and depleting, for half the time, the batteries are regenerating, building energy, and for the other half, the batteries are depleting.

Because our biorhythms flow as a wave, there is one day of change from high to low and back again, between the high and the low, which is referred to as a "Critical" day. The critical line or cross-over point divides the top half of the graph from the lower half, and is the point at which we switch over from recharging to expending energy or from expending energy to recharging. This is the major volatile point of change in our continuing wave of change. The "critical line or cross-over point" is the day when we are most vulnerable - physically, emotionally or intellectually - depending on which biorhythm line is crossing the critical line. It's the time when we are changing direction, from outward-looking to inward-looking, or vice-versa, and is likely to be a period of confusion, illness, or crisis. This cross-over point is when we are most likely to be suffering. When you pass through this central point - on that day and even on the day before (a preview of things to come), everything may go haywire in our life!

The validity of biorhythms have been proven over and over. There are number of studies that point to the value of monitoring your biorhythms. They help to explain to part everything from having a bad week to exciting scientific things like the varied effects medications have when administered at different times.

Our Free Biorhythm Calculators let's you overlay the Weekly astroMap on the Biorhythm Chart to help you get a better picture. With the Weekly astroMap overlaid, you can quickly spot your "high days" and "low days". If the astroMap is positive along with the biorhythm, those days can be unusually good. When the astroMap is negative along with the biorhythm, those days can be a real challenge. When you monitor these cycles over time, you will see how the different combinations of cycles and phases affect you.