Definition · 紫微斗數 · Purple Star Astrology

What Is Zi Wei Dou Shu?

Zi Wei Dou Shu (紫微斗數), often translated as Purple Star Astrology, is a traditional Chinese birth-chart system. It converts a birth date and a two-hour birth period into a chart of twelve palaces, each standing for one area of life. Fourteen major stars and a set of supporting stars are placed across those palaces, then read together with the Four Transformations and ten-year cycles. Unlike BaZi, which centres on stems, branches, and Five-Element relationships, Zi Wei Dou Shu organises its reading by life domain.

Chinese: 紫微斗數 (Traditional), 紫微斗数 (Simplified)
Pinyin: Zǐ Wēi Dǒu Shù
Also known as: Purple Star Astrology, Emperor Star Astrology, ZWDS, Zi Wei astrology
Input: Birth date (Gregorian or lunar), a two-hour birth period, gender for cycle direction
Output: 12 palaces, 14 major stars plus auxiliary stars, Four Transformations, ten-year and annual cycles
Origin: Traditionally attributed to Chen Tuan (陳摶, 10th century); the main surviving text, 紫微斗數全書, is a Ming-dynasty compilation
Used in: Taiwan, Hong Kong, mainland China, Southeast Asian Chinese communities; increasingly in English
Sister system: BaZi, the Four Pillars of Destiny, which reads the same birth moment through stems and branches

What a Zi Wei Dou Shu chart contains

A chart is a square of twelve cells, one for each Earthly Branch position, with the birth data written in the centre. Every layer below is placed by rule from the birth data; nothing is chosen by the reader.

Layer	What it is	How many
Palaces	Life domains: Life, Siblings, Spouse, Children, Wealth, Health, Travel, Friends, Career, Property, Wellbeing, Parents	12
Major stars	The principal named stars, split into the Zi Wei series and the Tian Fu series	14
Auxiliary stars	Assistants and scholars (左輔右弼文昌文曲天魁天鉞祿存天馬) and the sha stars (擎羊陀羅火星鈴星地空地劫), plus many minor stars	dozens
Four Transformations	Lu, Quan, Ke, Ji labels attached to four stars according to the birth-year stem	4
Brightness	Each major star's strength at its branch, on a seven-step scale from 廟 to 陷	1 per star
Cycles	Ten-year decades that move one palace at a time, then annual and monthly layers	12 decades

How the chart is built and read

The Gregorian birth date is converted to the Chinese lunar calendar; the birth time is reduced to one of twelve two-hour branches.
The lunar month and the birth hour fix the Life Palace. The other eleven palaces follow in a fixed counter-clockwise order.
The Life Palace's stem and branch give the Five-Element Bureau (Water 2, Wood 3, Metal 4, Earth 5, Fire 6), which sets the first decade and the position of the Zi Wei star.
The remaining thirteen major stars sit at fixed offsets from Zi Wei and Tian Fu. Auxiliary stars are placed from the year stem, year branch, month, and hour.
The birth-year stem assigns the Four Transformations to four stars.
Reading starts at the Life Palace and its three related palaces (San Fang Si Zheng), then moves to whichever domain the question is about, then to the current decade and year.

The full step list, with the conventions that make two calculators disagree, is on how a Zi Wei Dou Shu chart is calculated.

Worked example

Take a fictional birth: 6 February 1995, 15:00 to 17:00 (Shen hour), male. The lunar date is the 7th day of the 1st lunar month, 1995 (乙亥 year). The Life Palace lands at 午 with Zi Wei itself resident, the Body Palace is the Career Palace at 戌, and the bureau is 木三局 (Wood, 3), so the first decade runs from ages 3 to 12. The year stem 乙 gives Lu to Tian Ji, Quan to Tian Liang, Ke to Zi Wei, and Ji to Tai Yin.

A reader would begin with the Life Palace (Zi Wei, bright, carrying Ke), look across to the Travel Palace opposite (Tan Lang) and to the Wealth and Career palaces in trine (Wu Qu with Tian Xiang; Lian Zhen with Tian Fu), and only then say anything about disposition. The same chart is drawn as the sample wheel on the calculator page.

Zi Wei Dou Shu compared with BaZi

Both systems start from the same birth moment. BaZi writes it as eight characters and reads element balance around the Day Master; Zi Wei Dou Shu maps it onto twelve life domains and reads star placements. Zi Wei is usually the more detailed of the two on a specific domain (money, marriage, career), while BaZi is the more compact on overall constitution and timing. The side-by-side comparison covers calendar differences, timing layers, and which to learn first.

What Zi Wei Dou Shu is not

Not the Chinese zodiac. The zodiac animal comes from the birth year alone and is shared by everyone born that year. A Zi Wei chart needs the month, day, and hour, and changes with each.
Not Western astrology. The "stars" are named positions placed by calendar arithmetic, not observed planets. Tai Yang and Tai Yin are named after the sun and moon but are not astronomical positions of either.
Not a prediction engine. The chart is fixed at birth and describes tendencies and timing. What a person does with a tendency is outside the chart, which is why kaucim.ai reads it as a mirror rather than a verdict.

Schools and where they differ

San He (三合派): The most widely taught lineage. Reads palaces in trine with their opposite, uses brightness heavily, and applies the Four Transformations from the birth-year stem. kaucim.ai follows San He conventions, including the rule that a late-Zi birth stays on the same calendar date.
Fei Xing (飛星派, Flying Star): Uses the stem of each palace to "fly" transformations from palace to palace, tracing cause and effect between domains. Brightness matters less; the transformation paths matter more.
Zhongzhou (中州派): A Hong Kong lineage with its own placement details and a different transformation row for some stems. Software that offers a Zhongzhou mode changes a few star seats and the 庚 transformation row.

The differences are real but bounded: the palaces, the fourteen stars, and the first decade are the same everywhere. What moves between schools is a handful of auxiliary-star seats, two rows of the transformation table, and the weight given to each layer.

Common mistakes

Entering a lunar birth date as if it were Gregorian, or the reverse. The whole chart shifts.
Reading one palace on its own. A palace with no major star is normal (two palaces in the worked example are empty) and is read by borrowing from its opposite.
Treating Hua Ji as a curse. It marks fixation or obstruction in one domain, and it is present in every chart.
Comparing charts from two calculators that use different day-boundary or leap-month rules and assuming one of them is broken.

Questions people ask

Is Zi Wei Dou Shu the same as Purple Star Astrology?

Yes. Purple Star Astrology is the usual English rendering of 紫微斗數, named after the Zi Wei star, whose name is often glossed as the purple or imperial star. ZWDS is the common abbreviation.

Do I need my exact birth time?

You need the two-hour branch, not the minute. Births within about half an hour of a branch boundary are the ones worth checking, because the Life Palace and every star placement depend on the hour. Without any hour, a chart can still be cast at a reference hour, but its Life and Body Palace are not established.

Is Zi Wei Dou Shu more accurate than BaZi?

Neither is more accurate; they model different things. Zi Wei is more granular by life domain, BaZi is more compact on element balance and timing. Practitioners often use both on the same birth as a cross-check.

Can a chatbot cast a Zi Wei chart?

General language models routinely misplace stars and decades when asked to cast directly. The reliable pattern is a deterministic engine for the chart and, if wanted, AI only for explaining the fixed result. That is how the kaucim.ai calculator is built.

Sources and calculation version

iztro documentation · the open-source engine that casts every chart on kaucim.ai
kaucim.ai methodology · what is calculated and what AI is allowed to do
Calculation assumptions · the exact conventions in force

Last checked against the chart engine on 2026-09-14.

Read the definition, then see it on your own birth: the twelve palaces are calculated and shown before anything is interpreted.

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