The BaZi hour stem table

How to read the table

The branch comes from where the sun was at your birthplace; the stem follows mechanically from your day pillar's own stem — for each of the twelve branches there are only ten possible pillars, so the full mapping fits in one table.

1. Find your day pillar's stem — the first character of your third pillar. That selects the row. (Not sure? Start from the Day Master.)
2. Find your hour branch — decided by true solar time, not the clock (see below). That selects the column.
3. The cell is your hour pillar.

Each cell names the pillar; the small line under it is the branch animal. The 子 column here covers early zi only — 00:00 to 00:59, the half after midnight. If you were born between 23:00 and 23:59, use the midnight-boundary table below instead: late zi follows a different rule, and the schools also disagree about which day it belongs to.

Worked examples

A Yi Si (乙巳) day with a birth in the Chou window: find 乙 in the left column, 丑 along the top — the cell reads 丁丑, Yin Fire on the Ox. A Xin Hai (辛亥) day born in the Wu window reads 甲午: that second example is not an invented illustration but a case in our public verification corpus — 15 June 1990, noon, Hong Kong — where its correction chain is printed step by step: longitude, equation of time, true solar time.

If you don't know your birth time

Then these tables have nothing honest to offer you yet — the hour pillar cannot be guessed into existence. Our calculator returns three pillars and refuses to invent the fourth, because a default like “midnight” would quietly manufacture a zi-hour pillar sitting on the most consequential boundary in the chart (stated convention). Get your birth time from a birth certificate or family record first; the rest of the chart does not depend on it.

Where these tables come from

They are generated at build time by the same engine that casts every chart on this site, and they are re-checked on every build: against the arithmetic rules stated above, against all 32 timed cases in the public test corpus — including 4 genuine late-zi births routed to the midnight table — and against published known-good charts. If the engine ever drifts, through a dependency upgrade or anything else, the build fails instead of quietly publishing a different table.

Cast a chart and the hour pillar appears with its whole derivation chain — the calculator is free and needs no sign-up. To see how the pillars read together, read a complete sample report.