Your Kua number, your trigram, and the eight directions of the Eight Mansions system — each with its compass sector.
Li Chun year boundary · directions derived from the bagua, then checked against published tables
The Kua number comes from the year of birth and gender, but the year is the solar year, which begins at Li Chun in early February. Someone born on 20 January 1985 has the Kua number of 1984. Calculators that split the year on 1 January get roughly five weeks of every year wrong, and this page tells you when your own date falls in that window.
Feng shui is old, though not as old as it is usually sold. The classic Eight Mansions manual, the Ba Zhai Ming Jing, is a Qing-dynasty text that credits the Tang monk Yi Xing; the siting practice behind it is much older, and neolithic Yangshao graves at Puyang were already laid out on a north-south axis around 4500 BC. The Kua number itself is a later, compact way of asking the same question: which of the eight trigrams does a person belong to, and which of the eight sectors of a house therefore suits them.
The system spread with the Chinese diaspora; the Hong Kong and Malaysian schools of the twentieth century are where most English-language feng shui comes from, which is why competing tables sometimes disagree about women born in year 5. This page derives the table instead of copying one, and says so below.
What the number means for your house. Your four good directions are directions you face — the way your head points in bed, the way you sit at a desk, the way the front door opens when you look out of it. They are not the corner of the house you must live in, and they have nothing to do with the house number on the street. Neither does the number 8, however it is sold.
The eight directions are not a lookup table here. Each of the eight stars corresponds to flipping particular lines of your trigram in the Later Heaven arrangement — Sheng Qi flips the top line, Jue Ming flips all three, and so on. The table is generated from that rule and then compared cell by cell with published Eight Mansions tables. All 64 cells agree.
Two common reasons. First, the year: the Kua year turns at Li Chun in early February, so a January birthday belongs to the previous year. Calculators that split the year on 1 January disagree with this one for about five weeks of every year. Second, Kua 5: it has no trigram, so it is reassigned — to 2 for men and 8 for women in the most widely used convention, which is the one used here.
Neither. They are two halves of the same eight directions. Roughly half the population falls in each, and every Kua number gets exactly four good and four bad directions.
The classical use is facing direction: which way your head points when you sleep, which way you look when you work, which way your main door opens. Start with one — usually the desk — rather than rearranging a whole home.
In the classical method, yes: men subtract from 10 (or 9 from 2000 on) and women add 5 (or 6). This calculator follows the classical formula rather than inventing a neutral branch that no school uses.