A property's hexagrams are fixed by its construction; the occupants change. Xuan Kong Da Gua (玄空大卦) provides a precise method for matching individual occupants to specific bedrooms, offices, and primary-use sectors based on their personal hexagram (derived from birth Heavenly Stem + Earthly Branch). When occupants live in compatible sectors, the property amplifies their natural strengths. When mismatched, even a "good Feng Shui" property produces friction.
Calculating personal hexagram
Each person has a personal hexagram derived from their full Ba Zi day pillar (Heavenly Stem + Earthly Branch) combined with their gender. The 64 hexagrams map onto people the same way they map onto compass directions — each person resonates strongly with 4-8 of the 64. Most XKDG software calculates this; if doing by hand, the source table is in the classical Feng Shui texts of the San Yuan school. The calculation is one-time per person — your personal hexagram does not change.
Bedroom assignment in a household
In a household, bedroom assignment per XKDG produces dramatically different outcomes than picking by size or convenience. The principle: assign each person to the bedroom whose primary hexagram matches or productively combines with their personal hexagram. For couples sharing a bedroom, the bedroom hexagram should support both — usually the family-formation or partnership-class hexagrams (Hexagrams 31, 32, 53, 54 in the I Ching). Children's rooms benefit from learning-class hexagrams (4, 20, 26). Mismatched bedroom assignment is the #1 source of "good house, struggling family" patterns in audit work.
When the property hexagram does not match
Sometimes a property has a strong hexagram in a sector that none of the occupants resonate with. In this case, the sector is "unread" — its energy is present but not being received. Practical remediation: use that sector for activities that benefit from neutral energy (storage, utility, occasional guest space) rather than primary-use rooms. Alternatively, place objects symbolically connected to the hexagram (water imagery for Kan-class hexagrams, fire colours for Li-class) to keep the sector active even without an occupant resonance. The goal is balance between the property's structure and the people inside it.