How to Calculate Your Biorhythm from Your Birth Date

To calculate your biorhythm for a specific date, you first need to determine where your three personal cycles are at that moment:

• physical: 23 days;

• emotional: 28 days;

• intellectual: 33 days.

The starting point is your date of birth.

From there, you calculate the number of days lived up to the date you want to examine. The same number is then used separately to determine your position within each of the three cycles.

The principle is:

date of birth → days lived → position within the 23-28-33 cycles

Here is how it works in practice.

What Information Do You Need to Calculate a Biorhythm?

To perform the calculation, you only need:

• your date of birth;

• the date you want to observe.

You do not need:

• time of birth;

• place of birth;

• zodiac sign;

• name;

• any other personal information.

The calculation is based on the number of days that have passed since birth.

From Days Lived to the Three Cycles

Once the number of days lived has been determined, it is compared separately with the three cycle lengths.

For the physical cycle, use 23.

For the emotional cycle, use 28.

For the intellectual cycle, use 33.

The remainder obtained from each division indicates the position reached within that cycle.

In simple terms:

days lived ÷ 23 → position in the physical cycle

days lived ÷ 28 → position in the emotional cycle

days lived ÷ 33 → position in the intellectual cycle

Because the three cycles have different lengths, the resulting positions can also be very different.

A Practical Biorhythm Calculation Example

Consider a person born on June 15, 1990, and suppose we want to observe their biorhythm on September 2, 2026.

Counting the day of birth as the first day lived, the total is:

13,229 days lived

Now we apply the same number to each of the three cycles.

Physical Cycle Calculation

The physical cycle lasts 23 days.

13,229 divided by 23 gives a position of:

4 out of 23

The person is therefore on the fourth day of their physical cycle.

Emotional Cycle Calculation

The emotional cycle lasts 28 days.

13,229 divided by 28 gives a position of:

13 out of 28

The person is therefore on the thirteenth day of their emotional cycle.

Intellectual Cycle Calculation

The intellectual cycle lasts 33 days.

13,229 divided by 33 gives a position of:

29 out of 33

The person is therefore on the twenty-ninth day of their intellectual cycle.

We can summarize the result as follows:

Physical cycle — 23 days
Position: 4 / 23

Emotional cycle — 28 days
Position: 13 / 28

Intellectual cycle — 33 days
Position: 29 / 33

The observed date is the same, but the three positions are different.

This is an essential point for understanding biorhythms.

Why Are the Three Positions Different?

All three cycles begin at birth, but they have different lengths.

When the physical cycle completes its 23 days, it starts again.

The emotional cycle completes its period after 28 days.

The intellectual cycle after 33 days.

As time passes, the three cycles therefore move into continuously changing combinations.

In our example:

• the physical cycle is at 4/23;

• the emotional cycle is at 13/28;

• the intellectual cycle is at 29/33.

It would therefore be inaccurate to assign the person a single overall biorhythm position.

The profile for that day comes from reading all three results together.

From the Calculation to the Biorhythm Chart

The numbers tell you where you are within each cycle, but a chart makes the movement much easier to understand.

Each cycle is represented as a curve that develops over time in relation to a central line.

The chart makes it possible to observe:

• the position of each cycle;

• the phase it is passing through;

• the direction of movement;

• transition points;

• the relationship between the three cycles.

The reading should therefore not stop at the question:

“Is the curve above or below the line?”

You should also observe where the curve is and where it is moving next.

How to Read High and Low Phases

In the classic biorhythm representation, each cycle passes through a first and a second half.

High Phase

The first half is represented above the central line and is referred to as the high phase.

Low Phase

The second half is represented below the central line and is referred to as the low phase.

It is important not to automatically interpret these terms as:

high = good

low = bad

They are simply two parts of the same cyclical movement.

For a more complete reading, the exact position and direction of the curve should also be considered.

Why the Direction of the Cycle Matters

Two points that appear similar on a chart may actually belong to different moments in the cycle.

This is why it is not enough to look at a value or position in isolation.

It is also useful to ask:

• is the cycle rising or falling?

• is it close to a transition point?

• is it near an inversion point?

• what are the other two cycles doing at the same time?

It is the combination of these elements that provides a more complete reading.

Critical Days

Within each cycle, there are crossing points that require particular attention when interpreting the chart.

These are examined within the model through critical days.

Critical days are a specific aspect of biorhythm analysis and should not be confused with the entire high or low phase of a cycle.

→ Further reading: What Are Biorhythm Critical Days and When Do They Occur?

Keeping these concepts separate helps avoid assigning the same meaning to every point on the curve.

A Biorhythm Cannot Be Read from One Curve Alone

Suppose that on a particular day the chart shows:

Physical: high phase
Emotional: close to a transition point
Intellectual: low phase

Simply saying:

“My biorhythm is high today”

would be inaccurate.

The physical and intellectual cycles are describing different situations, while the emotional cycle is in yet another condition.

A more useful question is:

Where is each of my three cycles right now?

This is the difference between looking at a single number and reading a biorhythm profile.

Your Biorhythm Changes with the Date You Observe

The calculation does not produce a static result.

If you move the observation date forward by one day, each of the three cycles also advances by one day.

As a result:

• the physical position changes;

• the emotional position changes;

• the intellectual position changes.

The following day therefore produces a new configuration.

This makes it possible to observe your biorhythm not only for today, but across a longer period and follow the evolution of all three cycles over time.

Manual Calculation and Automatic Calculation

Manual calculation is useful because it helps explain the logic behind the system.

But when you want to observe a longer period, a chart becomes much more effective.

An automatic system can immediately transform:

date of birth + observation date

into the three physical, emotional and intellectual curves.

This allows you to focus less on the arithmetic and more on understanding the result.

From Personal Biorhythm to Comparing Two People

Everything described so far concerns one person.

It should not be confused with compatibility.

A personal biorhythm answers the question:

Where are my cycles on this date?

Compatibility between two people answers a different question and uses their respective dates of birth to build the comparison.

There is also BIORHYTHM COMPARISON, which allows the biorhythm situations of two people to be observed on a specific day or during a specific period.

These analyses are connected, but they are not the same.

Calculate Your Personal Biorhythm with byourit

With byourit, the calculation is performed automatically.

By entering your date of birth, you can see the position of your three cycles and observe their movement on a chart.

The advantage is not simply avoiding manual calculations.

It is being able to see immediately how your physical, emotional and intellectual cycles combine on the date you are observing.

Calculate your personal biorhythm and see where your three cycles are today.