The Eight Trigrams form the foundation principles of the Compass School of Feng Shui, which states that there are favourable and unfavourable directions, and locations, within a space that will have positive and negative effects on the occupant directly. These directions and locations are determined by the Gua (or Kua) Number of the person, which is calculated according to the person's gender and date of birth.

Gua Numbers are used in the practice of the Compass School of Feng Shui, which provides specific information on favourable and unfavourable directions for each number. These then form the basis from which, a space is assessed to improve its compatibility with the person, either by applying the Five Elements principles to devise cures, and/or by applying the Form School principles.

According to the Compass School teachings, each person carries a personal Gua Number between the numbers 1 and 9. Of these, only the numbers 1,2,3,4,6,7,8 and 9 are used: the number 5 is considered the central number and is not used as a personal Gua Number.

These eight Gua Numbers (discounting the centre) are then divided into two Groups; namely The East Group and The West Group, as shown below:

· East Group are Gua Numbers 1, 3, 4, and 9

· West Group are Gua Numbers 2, 6, 7, and 8 (Centre 5 also belongs to this Group)

The favourable and unfavourable locations and directions differ between the East and West Groups, while the Gua Numbers within the each Group share similar favourable and unfavourable locations and directions. Hence:

Before we proceed, you must be aware that these calculations always refer to the beginning of Spring as the start of the Year of Birth, which always falls on either the 4th or 5th of February of each year. Here we are referring to the February of the standard Gregorian calendar that we, and the rest of the world, use every day.

The formula used to calculate the Gua Number of a person is based on the Year of Birth. However, as mentioned earlier, if the Date of Birth falls before the beginning of Spring, then the previous year is used. The following examples use a formula that is actually Y2K compliant in that it takes care of the rollover from the 20th Century (19xx) to the 21st Century (2xxx) in the birthdates.

· 1 + 9 + 6 + 6 = 22
· 2 + 2 = 4

For Males, subtract resultant from 11 or (11-N): Gua Number is (11-4) or 7.

For Females, add 4 to the resultant or (4+N): Gua Number is (4+4) or 8.

· If the result yields a 5 Gua Number, then the same rules apply as in the previous formulae: use Gua Number 2 for Males and Gua Number 8 for Females.

· If the resultant is greater than 9 (10 or greater) then continue to add the digits together to arrive at the final Gua Number.