The month pillar is the second of your four pillars, and it is the one most people get wrong. The branch is easy: it comes from the season you were born into. The stem is where the bazi month stem table earns its keep, because the month stem is not free to be anything. It is fixed by the stem of your birth year through a rule the classics call the Five Tigers (五虎遁 wǔhǔdùn). Learn the table once and you can read the month stem for any birth chart without a calculator.
What the Five Tigers rule (五虎遁) actually says
Every solar year in Ba Zi (八字 bāzì) begins with the Tiger month (寅 Yín), which starts at Li Chun (立春 lìchūn), around 4 February. The Five Tigers rule tells you which heavenly stem sits on that first Tiger month, given the stem of the year. Once the first month’s stem is set, every following month simply advances one stem in the ten-stem cycle. So the whole year’s month stems fall out of a single starting point.
The year stems pair up into five groups that share the same column, which is why the rule counts “five” tigers: 甲 and 己 (Jiǎ and Jǐ), 乙 and 庚 (Yǐ and Gēng), 丙 and 辛 (Bǐng and Xīn), 丁 and 壬 (Dīng and Rén), 戊 and 癸 (Wù and Guǐ). Each pair opens its year on the same Tiger-month stem.
The complete bazi month stem table
Read down the month branch on the left, then across to your year-stem column. The cell is the full month pillar, stem and branch together.
| Month (branch) | 甲 / 己 year | 乙 / 庚 year | 丙 / 辛 year | 丁 / 壬 year | 戊 / 癸 year |
|---|---|---|---|---|---|
| 1st — Tiger 寅 Yín | 丙寅 Bǐng Yín | 戊寅 Wù Yín | 庚寅 Gēng Yín | 壬寅 Rén Yín | 甲寅 Jiǎ Yín |
| 2nd — Rabbit 卯 Mǎo | 丁卯 Dīng Mǎo | 己卯 Jǐ Mǎo | 辛卯 Xīn Mǎo | 癸卯 Guǐ Mǎo | 乙卯 Yǐ Mǎo |
| 3rd — Dragon 辰 Chén | 戊辰 Wù Chén | 庚辰 Gēng Chén | 壬辰 Rén Chén | 甲辰 Jiǎ Chén | 丙辰 Bǐng Chén |
| 4th — Snake 巳 Sì | 己巳 Jǐ Sì | 辛巳 Xīn Sì | 癸巳 Guǐ Sì | 乙巳 Yǐ Sì | 丁巳 Dīng Sì |
| 5th — Horse 午 Wǔ | 庚午 Gēng Wǔ | 壬午 Rén Wǔ | 甲午 Jiǎ Wǔ | 丙午 Bǐng Wǔ | 戊午 Wù Wǔ |
| 6th — Goat 未 Wèi | 辛未 Xīn Wèi | 癸未 Guǐ Wèi | 乙未 Yǐ Wèi | 丁未 Dīng Wèi | 己未 Jǐ Wèi |
| 7th — Monkey 申 Shēn | 壬申 Rén Shēn | 甲申 Jiǎ Shēn | 丙申 Bǐng Shēn | 戊申 Wù Shēn | 庚申 Gēng Shēn |
| 8th — Rooster 酉 Yǒu | 癸酉 Guǐ Yǒu | 乙酉 Yǐ Yǒu | 丁酉 Dīng Yǒu | 己酉 Jǐ Yǒu | 辛酉 Xīn Yǒu |
| 9th — Dog 戌 Xū | 甲戌 Jiǎ Xū | 丙戌 Bǐng Xū | 戊戌 Wù Xū | 庚戌 Gēng Xū | 壬戌 Rén Xū |
| 10th — Pig 亥 Hài | 乙亥 Yǐ Hài | 丁亥 Dīng Hài | 己亥 Jǐ Hài | 辛亥 Xīn Hài | 癸亥 Guǐ Hài |
| 11th — Rat 子 Zǐ | 丙子 Bǐng Zǐ | 戊子 Wù Zǐ | 庚子 Gēng Zǐ | 壬子 Rén Zǐ | 甲子 Jiǎ Zǐ |
| 12th — Ox 丑 Chǒu | 丁丑 Dīng Chǒu | 己丑 Jǐ Chǒu | 辛丑 Xīn Chǒu | 癸丑 Guǐ Chǒu | 乙丑 Yǐ Chǒu |
The formula, if you would rather compute it
The starting Tiger-month stem follows a compact rule. Number the ten stems from 甲 = 0. Take your year stem’s index, reduce it modulo 5, multiply by two, then add two: that gives the index of the first month’s stem. Each later month adds one, wrapping around at ten. A 甲 year has index 0, so (0 × 2) + 2 = 2, which is 丙 — the Tiger month is 丙寅, exactly as the table shows. You will rarely need the arithmetic once the five starting stems are memorised, but it is a good check.
A worked example
Suppose a chart has a 甲 (Jiǎ) year stem and the person was born in the Pig month (亥 Hài), the tenth month. Run down the Pig row to the 甲 / 己 column and you land on 乙亥 (Yǐ Hài). That is the month pillar. Notice the branch 亥 was decided by the season and the stem 乙 by the Five Tigers rule — two independent facts meeting in one cell. For the same Pig month but a 丁 (Dīng) year, the pillar becomes 辛亥 (Xīn Hài) instead. The branch never moves; only the stem shifts with the year.
The boundary warning that trips calculators
Months in Ba Zi change at the exact moment of a major solar term (節 jié), not on the first of a calendar month and not at the new moon. The Tiger month opens at Li Chun around 4 February, the Rabbit month at Jing Zhe (惊蛰 jīngzhé) around 6 March, the Dragon month at Qing Ming (清明 qīngmíng) around 5 April, and so on through Xiao Han (小寒 xiǎohán) around 5 January for the Ox month. A birth on 5 March may still belong to the previous month if Jing Zhe has not yet arrived that year, and the whole month pillar changes with it. The season also sets the year: someone born on the morning of 4 February 1988 was born before Li Chun that day, so their chart still uses the prior year’s stem. Because these moments drift by a day or two each year and are given in China Standard Time, this is exactly where hand calculation goes astray. Confirm the boundary before you trust the pillar.
Where the month pillar goes from here
The month stem and its branch decide far more than a date. The branch carries the seasonal energy that largely determines whether your Day Master runs strong or weak, and the month palace speaks to career climate and parents. For the year-by-year breakdowns, see the dedicated tables for Jia 甲 years and Ding 丁 years, and read the companion hour stem table, which uses the same five-fold logic to fix the hour stem from the day stem. The heavenly stems and earthly branches behind all of this are set out in the 22-character alphabet.
Find your own month pillar without second-guessing the solar-term boundary — plot your full chart free with the Butcher Boy calculator, then come back to this table to see how the Five Tigers rule built it.