Bazi (Four Pillars) chart calculator. Birth date + hour → 4 pillars (year/month/day/hour) with stem+branch+element+hidden stems+ten gods. Cultural reference.
Bazi Chart Calculator (八字排盘)
How to use
Enter Gregorian birth date
Pick a Gregorian birth date. The tool converts to lunar internally. Supported range: 1900-2100.
Pick birth hour
Enter as HH:MM. Hour-precision is enough (the classical system uses 2-hour blocks). Don't know your exact time? Choose 12:00 for a close approximation.
Pick gender
Gender does not change the pillars, Ten Gods or element counts this tool shows. In the tradition it only decides whether the 大运 (luck pillars) run forward or backward, and this tool does not compute 大运.
Read the chart
You get 4 pillars (year/month/day/hour), each with stem + branch + element + hidden stems + 纳音 + ten-god label. The bar chart at the bottom shows 五行 distribution — useful for spotting excess/deficiency at a glance.
Bazi (Four Pillars): The Core System of Chinese Metaphysics
Bazi — literally "Eight Characters" — also called the Four Pillars system, is the most important and widely-practised branch of Chinese 命理 (fate-reading) tradition, built up across generations of classical fate-reading literature and still the mainstream framework in Chinese-language practice today. The system converts a person's birth year, month, day, and hour into 4 pairs of Heavenly Stem (天干) + Earthly Branch (地支) — 8 characters total, hence the name. Each stem-branch pair is one pillar, and the 4 pillars together form a complete birth chart (命盘).
What each pillar represents
The year pillar represents ancestors + early life (0-15); the month pillar represents parents + youth (16-30); the day pillar represents the self + spouse (31-45, with the day-stem being the "day master" / personal anchor); the hour pillar represents offspring + later life (46+). This four-stage life division is referenced throughout classical bazi analysis.
Reading the Five Elements
Each of the 8 characters belongs to one of the Five Elements (木 wood, 火 fire, 土 earth, 金 metal, 水 water). Their distribution reveals chart balance: excess of one is "strong"; absence is "weak". Classical theory values balance — well-mixed charts are considered hardest to attain and most propitious. The bar chart below shows distribution at a glance.
What a bazi chart shows is never fate's certainty, only fate's possibility — the chart is fixed, what you do with it is not.
Disclaimer + cultural stance
This tool computes bazi from a public algorithm and does not constitute professional advice. Bazi is part of Chinese cultural heritage; its scientific validity as a predictive tool is not supported by modern statistical research. We provide this tool for cultural-tradition preservation + entertainment reference, NOT for major life decisions (marriage, career, health). Always combine with practical considerations and professional consultation. ASEAN Chinese communities (especially HK, Singapore, Malaysia, Indonesia) retain strong cultural interest in bazi; this tool is a self-service cross-reference, not a substitute for a local 命理师 practitioner.
Everyone born in the same two-hour block shares a chart
The traditional lineage account credits Li Xuzhong with reading fate by year, month, and day, and Xu Ziping with adding the hour pillar to complete the four-pillar system — which is where the alternative name 子平术 (Ziping system) comes from. The story is very widely repeated, though its specifics are hard to verify.
Four pillars × 60 stem-branch combos each = 12,960,000 possible bazi charts. But distribution is uneven — some are shared by thousands of people; others occur only once in 60 years.
Everyone born in the same 2-hour block on the same day shares an identical bazi. Singapore registered 33,703 live births in 2024 (Singapore Department of Statistics), about 92 a day or roughly 8 per 2-hour block, and each of those groups shares one chart. This is the central critique of bazi as a predictive tool.
The "day master" (day-pillar stem) is bazi's most important character — it represents the person. Every other character is read through its relationship to the day master. This is bazi's biggest contrast with Western astrology (which has no analogous focal point).
Perfectly balanced 五行 charts are rare: eight characters cannot split evenly across five elements, and most charts lean on one or two. That is why classical bazi books prescribe so many "补救" (remedies) — wearing certain colours, stones, name changes, directional arrangements.
Bazi 合婚 (marriage matching) is a millennia-old tradition — comparing two people's day-stem + year-branch for harmony/clash. Our companion Bazi compatibility tool handles this use case.
The "Ten Gods" (比肩 劫财 食神 伤官 正财 偏财 正官 七杀 正印 偏印) are bazi's core vocabulary — each character's yin-yang + element relationship to the day master determines its 十神 label. The tool auto-tags these.
In HK, Taiwan, Singapore, Malaysia, Indonesia Chinese communities, newborn bazi is still widely recorded (especially in birth-memory books). Mainland China retains it in some rural areas but practice has declined notably since the 1990s.
Bazi 大运 (10-year cycles) and 小运 (annual luck) are advanced reading dimensions — not covered in this basic chart tool. Consult a professional 命理师 or specialised software for those.
The bazi year begins at the moment of 立春 (Start of Spring), not on 1 January or at Lunar New Year. In 2024 立春 fell on the afternoon of 4 February, so a baby born that evening already has a 甲辰 year pillar, though Lunar New Year was not until 10 February.
Frequently Asked Questions
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Not scientifically validated. Bazi is a millennia-old cultural system, but the "many people share the same chart" phenomenon makes it fail modern statistical scrutiny. This tool does not endorse predictive accuracy — it's for cultural reflection + personal consideration only.
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Pick 12:00 for an approximation. Year/month/day pillars stay accurate (they only need birth date). Only the hour pillar + its associated 十神 are affected. If hour matters to you, check hospital/parental records — or skip hour analysis.
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Two common reasons: (1) 立春 boundary — this tool switches the year pillar at the Start-of-Spring solar term (~Feb 4), some tools use Gregorian Jan 1. (2) The 23:00 hour — for a birth between 23:00 and 23:59, this tool keeps that calendar day's day pillar and takes the hour pillar from the next day's 子 hour (e.g. 15 May 1990, 23:30 → day 庚辰, hour 戊子). Another school moves the day pillar to the next day from 23:00. Both are in use and neither is settled; if you were born in that hour, cast the chart both ways and compare.
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The day-pillar stem character. In a bazi chart, the day master represents the person themselves; every other character is interpreted through its relationship (same/conquers-me/I-conquer/produces-me/I-produce) to derive the Ten God labels. The day master's element gives your "element identity" (I'm metal/wood/water/fire/earth命).
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Each earth-branch contains 1-3 "hidden stems" (concealed heavenly stems) in addition to its main reading. For example 亥 contains 壬+甲; 未 contains 己+丁+乙. Hidden stems matter for fine-grained analysis — the visible 8 characters effectively represent 12-15 working characters.
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Yes — HH:MM precision. Classical bazi uses 2-hour blocks (子 to 亥), so minutes don't change the pillar unless you cross a boundary (e.g. 12:59 vs 13:01 switches from 午 to 未). The tool handles boundaries automatically.
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No. All computation is browser-local; no server calls. Even for sensitive metaphysical inputs, RECATOOLS enforces zero-tracking + zero-storage.
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Not as your only guide. Bazi is a cultural-reflection tool, not a decision tool. Major decisions (marriage, career, health, relocation) should rest on practical analysis, professional advice, and personal values. If bazi brings you cultural connection or psychological comfort, that's its value. If it makes you fearful or passive, ignore it.
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大运 are 10-year fortune cycles. 小运 (also "流年") are annual influences. They interact with the natal chart to produce "this decade's flavour" + "this year's flavour" readings. This tool covers the natal chart only; 大运/小运 requires a professional 命理师 or specialised software.
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The basic chart structure matches — stem/branch/element/Ten-God labels follow classical conventions: the hidden-stem and Ten-God tables are the standard ones set out in 《渊海子平》 (Yuanhai Ziping), and the 纳音 table follows 《三命通会》 (Sanming Tonghui). But higher-level interpretation (格局 chart patterns, 用神 favoured element, 调候 climate balancing) needs human analysis and isn't covered here. Treat this as an introductory + verification tool.
Method & sources
How it computes
Casts the Four Pillars from a Gregorian birth date and time using the vendored lunar-javascript sexagenary tables: the year pillar changes at the 立春 instant, the month pillar at each 節 solar term, the day pillar follows the continuous 干支 day count, and the hour pillar uses the twelve two-hour 時辰 with 23:00–00:59 as 子. Each stem and branch is then labelled with its 五行, hidden stems (藏干), 納音 and Ten God (十神) relative to the day stem.
What this tool implements
- Year pillar boundary is the 立春 instant, not 1 January or Lunar New Year: 2024-02-03 casts a 癸卯 year and 2024-02-04 17:00 (after 立春 at 16:27 Beijing time) casts 甲辰.
- 子時 handling follows the 分早晚子時 school (lunar-javascript 流派 2): a 23:00–23:59 birth keeps the current day's day pillar and takes the next day's 子 hour stem. The 子時換日 school moves the day pillar forward at 23:00 and gives a different chart for that hour.
- Hidden stems (藏干), 納音 and the ten 十神 labels follow the standard 子平 tables as recorded in 《淵海子平》 and 《三命通會》; 十神 are read relative to the day stem. The 五行 tally counts the eight visible characters only, not hidden stems.
- Gender is collected but does not change the cast chart: in the tradition it only fixes the direction of the 大運 luck pillars, which this tool does not compute. The chart is cast, not interpreted — no score, rating or prediction is produced. Bazi is presented as cultural reference; it is not a predictive or scientific method.
Sources
- 徐大升(宋).《淵海子平》. Chinese Text Project digital library: https://ctext.org/wiki.pl?if=gb&chapter=901791
- 萬民英(明).《三命通會》(收入《四庫全書》子部術數類). Chinese Text Project digital library: https://ctext.org/wiki.pl?if=gb&res=587236
- 沈孝瞻(清).《子平真詮》, 徐樂吾評註 (1936). Chinese Text Project: https://ctext.org/wiki.pl?if=en&res=631975
- Hong Kong Observatory. Gregorian-Lunar Calendar Conversion Table 1901–2100 (公曆與農曆日期對照表): https://www.hko.gov.hk/tc/gts/time/conversion.htm
- 6tail. lunar-javascript v1.7.7 (MIT) — 八字 documentation: 流派 (sect) rule for 晚子時 and 年柱以立春交接時刻為準: https://6tail.cn/calendar/lunar.bazi.html ; source repository: https://github.com/6tail/lunar-javascript
What can make this go out of date
- lunar-javascript is vendored at v1.7.7 and never fetched at runtime; an upstream correction to its solar-term or 干支 tables reaches this page only on a manual update.
- The 子時 school is a fixed editorial choice, not a data feed; switching it would change every chart cast in the 23:00–23:59 hour.
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