The Eight Trigrams of the I Ching 八卦 (Bāguà)

A trigram is three horizontal lines, stacked. Each line is either yang (a single solid line, ⚊) or yin (two short segments with a gap, ⚋). Three lines, two possibilities per line, gives 2 × 2 × 2 = 8 distinct configurations. Those eight configurations are the trigrams: 乾, 兌, 離, 震, 巽, 坎, 艮, 坤.

Each trigram is read bottom-up, the way a building is read from the foundation. Line 1 (the bottom) is the inner ground, the disposition. Line 2 (the middle) is the working layer. Line 3 (the top) is the outer face that meets the world. This bottom-up reading is not stylistic — it is structural. Every classical I Ching commentary from the Zhou Yi onward describes lines moving upward through time, not downward.

The character of each trigram comes from which positions are yang and which are yin. Three pure yang lines is 乾 (Heaven, the most active configuration in the system). Three pure yin lines is 坤 (Earth, the most receptive). The other six trigrams are mixed — one or two yin lines among yang, or vice versa — and each mixed configuration has a precise classical reading depending on which line is the “exception” in the pattern.

Two trigrams stacked produce a hexagram — six lines, again read bottom-up. There are 8 × 8 = 64 possible hexagrams, which is why the I Ching has exactly 64 chapters. The trigrams are the alphabet; the hexagrams are the words; the changing lines that activate during a divination are the syntax. To read the I Ching well, you have to know the eight trigrams. Everything else is decoration on top of that knowledge.

The binary correspondence (the Leibniz hook)

If you replace yang with 1 and yin with 0, the trigrams become the eight 3-bit binary numbers from 000 through 111 — with the top line read as the most significant bit (i.e., 111 = 乾, 000 = 坤, 010 = 坎, and so on). Gottfried Leibniz noticed this in 1703, in correspondence with the Jesuit missionary Joachim Bouvet, and called it “the most marvellous accord he could imagine.”

This is true and worth knowing — but it is also overstated by people who want to claim the Chinese invented binary computation. They didn’t. The trigrams encode three positions of a yes/no distinction; that is binary structurally, not computationally. The classical Chinese tradition never used trigrams to do arithmetic. The binary parallel is a mathematical curiosity that maps cleanly because both systems happen to enumerate combinations of two states at three positions. It is a footnote, not a revelation.

What the binary view is useful for: it gives you a precise, unambiguous way to refer to a trigram on a page. 011 is 兌 (Lake) regardless of whether the reader knows the Chinese character. The binary field on this page’s reference table uses the convention top-to-bottom, most-significant-bit-first — which matches both the Leibniz mapping and the way the Wilhelm/Baynes translation indexes the trigrams.

The table below is the canonical reference for all eight trigrams (八卦). Each row condenses the data a practitioner needs to read a hexagram quickly: the line composition, the family role, the Five-Element classification, the Pre-Heaven and Post-Heaven Bagua positions, and the “doubled” hexagram each trigram produces when stacked over itself. Click any Chinese name to open the full reference page for that trigram.

The Pre-Heaven Bagua (先天八卦, Xiāntiān Bāguà) is the older arrangement, attributed to the legendary sage Fu Xi (伏羲). It places the eight trigrams around an octagon in pairs of polar opposites: 乾 (pure yang) directly opposite 坤 (pure yin); 離 (Fire) opposite 坎 (Water); 震 (Thunder) opposite 巽 (Wind); 艮 (Mountain) opposite 兌 (Lake). Read across any diameter of the diagram and you find a pair whose line patterns invert each other line by line.

Pre-Heaven is the “ideal” arrangement — it shows the trigrams in their archetypal relations, before any seasonal or geographic specialisation. Time is not yet a factor; the year has not yet started turning. What you are looking at is the structural balance of the eight forces: every active configuration has its receptive complement on the opposite side. Heaven and Earth define the vertical axis. Fire and Water define the horizontal. The other four trigrams sit in the diagonals, each completing its complement.

Classical texts position Pre-Heaven as the diagram of the cosmos before manifestation — the configuration of the eight forces before they have begun to act through time. It is the diagram you turn to when the question is what something is, not when something happens or where it is. Meditation traditions that use the Bagua often work primarily with the Pre-Heaven sequence for this reason.

One small detail readers regularly trip over: classical Chinese diagrams place South at the top, not North. This is a Chinese cartographic convention that predates the bagua. The diagram above renders it the classical way. If you mentally rotate it 180°, you get the “Western” orientation — but every classical text and most reputable contemporary references draw it with 乾 (South, Heaven) up and 坤 (North, Earth) down.

The Post-Heaven Bagua (後天八卦, Hòutiān Bāguà) is the second classical arrangement, attributed to King Wen (文王) of the Zhou dynasty. It places the trigrams around the same octagon — but in completely different positions. Where Pre-Heaven is symmetrical and time-out-of-time, Post-Heaven is seasonal: it maps each trigram onto a quadrant of the year and a direction of the compass.

The mappings are precise and not negotiable. 震 (Thunder) goes east, the direction of spring — the trigram of new motion, on the quadrant where the year wakes up. 離 (Fire) goes south, the direction of summer — brightness at full height. 兌 (Lake) goes west, autumn — the gathering and the harvest. 坎 (Water) goes north, winter — the depth, the storage, the going-through. The diagonals (NE, SE, NW, SW) hold the four transitional trigrams.

Post-Heaven is the diagram practitioners use. Feng Shui’s eight life areas (the bagua you have heard about) are positioned by the Post-Heaven sequence. BaZi’s seasonal element strength (the reason a Yang Wood Day Master born in summer is “strong”) is read off the Post-Heaven map. Every directional reading in classical Chinese metaphysics — where to face for sleep, which corner of a building holds wealth energy, when in the year a particular trigram is most active — references this arrangement.

This is also the diagram the retail Feng Shui industry uses, and the diagram they most frequently misuse. The Post-Heaven Bagua is not a wall decoration. It is not a poster you place over your front door so that “the wealth corner faces inward.” It is a coordinate system for reading where each archetypal force is acting in a real space at a real time. The diagram is universal; what it tells you depends entirely on the building’s actual orientation, the chart of the people inside it, and the year you are reading. Putting up the diagram changes nothing.

The two arrangements are not in conflict. They are answering different questions, and a classical practitioner holds both diagrams in mind at once and switches between them depending on what is being asked.

Pre-Heaven (先天) describes what each trigram is. Use it when the question is structural: what is the essential nature of 坎 (Water)? What is the polar opposite of 離 (Fire)? Which two trigrams form a complement that reaches structural balance? Pre-Heaven gives the answer in its diagram of opposed pairs.

Post-Heaven (後天) describes when and where each trigram acts. Use it when the question is operational: what is the trigram of late spring? Which direction is governed by 坤 in current practice? Where in a building does 震 energy land? Post-Heaven gives the answer in its diagram of seasonal and directional mappings.

This is why the two arrangements give different positions for the same trigram. 乾 (Heaven) sits in the South in Pre-Heaven (its archetypal position, paired with Earth in the North) and in the Northwest in Post-Heaven (its operational position in the autumn-into-winter quadrant). Both placements are correct simultaneously. The trigram has two coordinates because the question has two valid frames.

Most pop-mysticism content collapses this into a single diagram — usually the Post-Heaven, treated as if it were the only one — and then claims the Pre-Heaven is “deeper” or “more spiritual.” That is not how the classical tradition works. The two are companion frames. A practitioner who only knows one of them is missing half the system.

The practical test for which to use: is the question about identity or about timing? Identity (what is this trigram, what does it mean structurally, who is the family member it represents) → Pre-Heaven. Timing or location (when is this active, where in space does it land, what season is its strength) → Post-Heaven. Decisions get easier once you have asked yourself this question first.

A hexagram is two trigrams stacked. The lower three lines form one trigram (the “inner” or “lower” trigram); the upper three lines form another (the “outer” or “upper” trigram). Read together, the two layers form a six-line figure that is one of the 64 hexagrams of the I Ching. The reading rule is simple: the upper trigram describes the outer face of the situation (what is publicly visible), the lower trigram describes the inner ground (the disposition or the foundation).

Each of the eight trigrams can pair with any of the eight as upper or lower, which is exactly how you get to 64 hexagrams — 8 × 8. Eight of those 64 are produced by stacking a trigram on top of itself. These are called the doubled or pure hexagrams, and each one represents the maximal expression of a single trigram’s nature, undiluted by any other force. The eight pure hexagrams — one for each trigram — are the structural anchors of the entire system. They are listed below.

For the full 64-hexagram system — including all the mixed pairings (e.g., 乾 over 坤, 坤 over 乾, and the 54 other combinations), each hexagram’s judgment text, line statements, and derived hexagrams (互卦 nuclear, 錯卦 inverse, 綜卦 reverse) — see the complete I Ching 64 Hexagrams reference. That page contains the same trigrams you see here, paired in every possible combination.

The eight trigrams are not just an I Ching tool. They are the shared vocabulary of three classical systems — the I Ching itself, BaZi (the Four Pillars of Destiny), and Feng Shui — and their power comes from the fact that the same eight figures show up in all three with consistent meanings.

In the I Ching

This is the trigrams’ native domain. When you cast a hexagram (with three coins, fifty yarrow stalks, or any modern equivalent), what you receive is two trigrams stacked. The reading then asks: which trigram is on top? which is on the bottom? The classical commentary structures itself around that question. The Image (大象) of every hexagram opens with a description of the upper-trigram-over-lower-trigram configuration: “Heaven over Earth: Tai. Heaven inside, Earth outside: Pi” — the hexagram’s identity comes from the trigram pair before it comes from anything else.

In BaZi (Four Pillars of Destiny)

BaZi reads a person’s chart through stem-and-branch pillars, but the trigrams sit underneath the system. Every Earthly Branch (the bottom half of a pillar) has a default trigram correspondence; every elemental phase (Wood, Fire, Earth, Metal, Water) has trigrams associated with it. When a practitioner says “your chart is heavy on 坎 energy” or “the year activates 震 on your day master”, what they mean precisely is that the seasonal Post-Heaven Bagua position of the year/luck pillar lines up with a particular trigram, and the trigram’s nature describes how the year acts on the chart. Plot your BaZi chart to see your own trigram alignment.

In Feng Shui

Feng Shui’s “eight life areas” bagua — the one printed on retail bagua mirrors and pamphlets — is the Post-Heaven Bagua mapped onto a building’s floor plan. Each trigram corresponds to a direction (the cardinal eight) and to a domain of life (career for 坎 in the north, fame for 離 in the south, and so on). The trigrams provide both the directional (which corner) and the elemental (which Five-Element correspondence) inputs that the practitioner reads against the year’s flying stars and the residents’ charts.

The cross-domain test

Here is the test that separates a real practitioner from someone who has memorised one of the three systems: ask them what 坎 (Water) means in the I Ching, in BaZi, and in Feng Shui. The answers should not contradict each other. They should be three views of the same archetypal pattern: in the I Ching, the trigram of going-through-difficulty; in BaZi, the energy of winter, of stored vitality, of the kidneys, of the deep; in Feng Shui, the north quadrant, the career area, the flowing water that connects rooms. If the three answers are wildly different, the practitioner is reciting from a textbook and has not done the integration. If they are clearly the same shape rendered three ways, the practitioner has the system.

The eight individual trigram pages each cover their own trigram in depth — line composition, the canonical Shuogua passage, the eight hexagrams in which the trigram appears, the doubled hexagram, and Five-Element correspondences. The hexagram hub covers the full 64-hexagram system. Lateral links go to the BaZi calculator and the 2027 zodiac forecast hub.