Heavenly Stems and Earthly Branches: the building blocks
Ten and twelve, cycling together into sixty — the oldest continuously used calendar in the world.
4 min read · Published 18 August 2026
The short answer
The ten Heavenly Stems are the five elements in yang and yin form. The twelve Earthly Branches are the animals you know from the zodiac, each also carrying an element and a two-hour period of the day. Paired together they generate a sixty-term cycle — ten and twelve have a lowest common multiple of sixty — that has been running continuously for millennia. Each branch also conceals one to three additional stems inside it, which is where much of the chart's real detail lives.
The ten Heavenly Stems
| Stem | Element | Polarity |
|---|---|---|
| 甲 Jia / 乙 Yi | Wood | Yang / Yin |
| 丙 Bing / 丁 Ding | Fire | Yang / Yin |
| 戊 Wu / 己 Ji | Earth | Yang / Yin |
| 庚 Geng / 辛 Xin | Metal | Yang / Yin |
| 壬 Ren / 癸 Gui | Water | Yang / Yin |
Five elements, two polarities, ten stems. Simple and complete. The stem of your day pillar is your Day Master.
The twelve Earthly Branches
| Branch | Animal | Element | Hours |
|---|---|---|---|
| 子 Zi | Rat | Water | 23:00–01:00 |
| 丑 Chou | Ox | Earth | 01:00–03:00 |
| 寅 Yin | Tiger | Wood | 03:00–05:00 |
| 卯 Mao | Rabbit | Wood | 05:00–07:00 |
| 辰 Chen | Dragon | Earth | 07:00–09:00 |
| 巳 Si | Snake | Fire | 09:00–11:00 |
| 午 Wu | Horse | Fire | 11:00–13:00 |
| 未 Wei | Goat | Earth | 13:00–15:00 |
| 申 Shen | Monkey | Metal | 15:00–17:00 |
| 酉 You | Rooster | Metal | 17:00–19:00 |
| 戌 Xu | Dog | Earth | 19:00–21:00 |
| 亥 Hai | Pig | Water | 21:00–23:00 |
Note that the branches carry hours as well as years. Your birth hour gives you a second animal, which most people have never been told — see Chinese zodiac hours.
Hidden stems: where the detail lives
This is the part that separates a real BaZi reading from a surface one. Each branch conceals additional heavenly stems inside it — usually one, two or three.
The Tiger branch (寅) is a Wood branch, but it hides 甲 yang Wood, 丙 yang Fire and 戊 yang Earth. The Rat (子) hides only 癸 yin Water. The proportions matter: the first hidden stem is the main qi, carrying most of the branch's strength, followed by middle and residual energies.
The consequence is that your chart contains considerably more than eight characters' worth of information, and an element you appear to be missing may be hiding inside a branch. A tool that ignores hidden stems will tell you that you lack Fire when you have three hidden Fire stems.
The sixty-year cycle
Pair the stems and branches in sequence — first stem with first branch, second with second — and because ten and twelve share a lowest common multiple of sixty, the combination repeats every sixty terms rather than every twelve.
This is the sexagenary cycle (干支), and it has been running continuously for well over two thousand years. It is why 2026 is 丙午, a yang Fire Horse year, and 2027 is 丁未, a yin Fire Goat year — the animal repeats every twelve years, but the full stem-branch pair only every sixty.
It also means only half the possible combinations occur. There is no yin stem with a yang branch, because the sequence pairs odd with odd and even with even.
Why this matters for reading a chart
Everything else in BaZi is built on these. The Ten Gods are relationships between stems. Clashes and combinations are relationships between branches. Strength depends on which stems are rooted in which branches.
Get the building blocks and the rest is derivation rather than memorisation, which is the same principle as learning tarot's numeric spine rather than 78 separate cards.
Common questions
- What are the Heavenly Stems and Earthly Branches?
- The ten Heavenly Stems are the five elements in yang and yin form. The twelve Earthly Branches are the zodiac animals, each also carrying an element and a two-hour period. Paired in sequence they generate the sixty-term sexagenary cycle.
- Why is the Chinese cycle sixty years and not twelve?
- Because ten stems and twelve branches cycle together, and the lowest common multiple of ten and twelve is sixty. The animal repeats every twelve years but the full stem-and-branch pairing only every sixty.
- What are hidden stems?
- Additional heavenly stems concealed inside each earthly branch — one to three per branch, with the first carrying most of the branch's strength. They mean a chart contains far more information than its eight visible characters, and an element that appears missing may be hidden inside a branch.
- Does my birth hour have an animal too?
- Yes. Each of the twelve branches governs a two-hour period, so your birth time gives you a second animal — the hour branch. It runs from the Rat at 23:00 to the Pig at 21:00.