i.

What is Zi Wei Dou Shu?

Zi Wei Dou Shu (紫微斗数), often translated as Purple Star Astrology or Emperor Star Astrology, is a Chinese astrological system developed during the Song Dynasty by the philosopher Chen Tuan (陈抟). Where BaZi is precise but compact — eight characters across four pillars — Zi Wei is architectural: a 12-palace map of life domains with 14 major stars and over 100 minor stars distributed across it.

Each palace governs a different domain: Self, Siblings, Spouse, Children, Wealth, Health, Travel, Friends, Career, Property, Fortune, Parents. The major star occupying each palace — and the surrounding stars in trine and opposition — give the reading its color.

ii.

The schools and which one we use

Zi Wei Dou Shu fractured into multiple lineages over the centuries. Three matter today: San-He (三合), Zhong-Zhou / Northern (中州), and Flying Star / Fei Xing (飞星). Their star placements differ in subtle ways, and their interpretation methods diverge significantly.

We use the San-He school as implemented in the open-source iztro library by SylarLong. This is the most common school taught in Taiwan and Hong Kong, and the most rigorously codified in modern English-language sources. If you have learned ZWDS from a Flying Star teacher, our star placements will mostly agree with yours — but the interpretive grammar will differ.

iii.

Why almost nothing exists for ZWDS in English

Zi Wei Dou Shu's complexity — 12 palaces × 14 major + 100+ minor stars × brightness levels × school variations — has kept most translators away. The English-language references that do exist are mostly translated from a single dialect of Taiwanese practitioners, often without naming the school.

We are not claiming this calculator is the final word. We are saying it is the first one we know of that calculates correctly, names its school, and refuses to gloss the technical decisions. See methodology for full algorithm sources.