How to Cast the I Ching: Yarrow Stalks, Coins, and Numbers

There are three live ways to build an I Ching hexagram, and they are not interchangeable. The yarrow stalk procedure is the oldest and takes about an hour. The three-coin method is the one almost everybody uses and takes about five minutes. The number method, plum blossom divination, takes about thirty seconds and needs no props at all.

They also do not produce the same odds. Yarrow stalks and coins give measurably different probabilities for a changing line, which means the two procedures do not sample the same distribution of readings. That difference is old, well documented, and almost never mentioned by the sites that cast hexagrams for you.

Here is how each one works, what it costs you in time, and how to choose.

Method one: the yarrow stalks

This is the procedure described in the classical commentaries, and it is the reference against which the others are shortcuts.

You need fifty stalks. One is set aside at the start and takes no further part, leaving forty-nine in play. Building a single line takes three passes through the bundle: divide it in two, set one stalk aside from the right-hand pile, then count both piles off in fours and collect the remainders. What survives the three passes resolves to one of four values, 6, 7, 8, or 9, and that value is the line.

Six lines at three passes each is eighteen operations, which is where the traditional figure of eighteen changes comes from. Done properly and unhurried, it takes forty-five minutes to an hour.

The time is the point, in the view of practitioners who keep the method. An hour of counting stalks is an hour spent with the question and no way to skip to the answer, and a good deal of what the procedure produces happens in the person rather than in the bundle.

Method two: the three coins

Three coins, six throws, roughly five minutes. This is the standard method in modern practice, Chinese and Western alike.

Assign one face of the coin the value three and the other the value two, and keep the assignment consistent for the whole cast. Throw all three coins together and add the values. The sum can only be 6, 7, 8, or 9, and that is your line.

Six is old yin, a yin line that is changing. Seven is young yang, a stable yang line. Eight is young yin, a stable yin line. Nine is old yang, a yang line that is changing.

Throw six times, and record the lines from the bottom of the hexagram upward. Every changing line flips to its opposite to produce the second hexagram, and the pair is read as a movement from the first to the second.

The difference nobody mentions

The two procedures assign different probabilities to the same four outcomes. This is arithmetic, not doctrine.

Two things fall out of that table.

Under yarrow, a changing yang line is three times as likely as a changing yin line. Change enters the reading predominantly through yang. Under coins, the two changing lines are equally likely, and the asymmetry disappears entirely.

Under coins, a hexagram with no changing lines at all is rarer, so coin casts tend to produce more movement per reading than stalk casts do.

Whether that matters is a question about what you think the procedure is doing. If the casting is a randomiser and the meaning lives in the interpretation, the distributions are a curiosity. If the distribution itself carries something, the coin method is a different oracle wearing the same name. The honest position is that this has been argued about for centuries and remains unsettled, and that anyone selling you a definitive answer is selling.

Method three: the numbers

The third route drops the props. Plum blossom divination, Mei Hua Yi Shu, builds the hexagram by division instead of by chance.

Take two numbers that surface on their own while you are holding the matter. Divide the first by eight and take the remainder to set the upper trigram, in the primal sequence Qian, Dui, Li, Zhen, Xun, Kan, Gen, Kun, with a remainder of zero counting as eight. Divide the second the same way for the lower trigram. Then add both numbers to the ordinal of the current double-hour, divide by six, and the remainder names the moving line, counting from the bottom.

Three divisions and the hexagram is finished. There is no probability distribution to argue about, because nothing is being randomised: the cast is a function of two numbers and a time.

The reading works differently too, leaning on the relation between the two trigrams rather than on the received line texts. Plum blossom divination explained covers the Ti and Yong relation that carries most of the interpretive weight, along with the nuclear and changed hexagrams the method reads alongside the primary one.

Because the arithmetic is exact and easy to get wrong by hand, this is the method most worth handing to a machine. The caster here runs the three divisions, prints every remainder so you can check it, and casts on Hong Kong time. It is free and takes no sign-in.

Which method to use

For a question that deserves an hour of your attention and has time to spare, the stalks. The procedure is most of the value.

For ordinary practice, the coins. Five minutes, low ceremony, and the method every English commentary is written against, so the line texts and the guides line up with what you cast.

For a matter that just surfaced, when you have no coins and no hour, the numbers. This is also the method that survives contact with a phone, which is why it has outlived the others in daily use across the Chinese-speaking world.

One rule crosses all three. Ask once. All three methods are built on a single question producing a single hexagram, and recasting the same words gives you a second valid answer with no principled way to choose between them. If you need to ask again, change the question rather than repeat it.

Two things that are not casting methods

Asking a chatbot for a reading is not a fourth method. Language models produce plausible hexagram commentary and routinely miscompute the arithmetic underneath it, particularly the remainders in the number method and the ordinal of the double-hour. A confident reading built on the wrong hexagram is worse than no reading, and the failure is invisible unless the working is shown.

Drawing a numbered stick is a different tradition, not a shortcut version of this one. Temple stick-drawing answers with a fixed verse and a grade rather than with a hexagram and its changes, and the two systems have separate texts, separate histories, and separate strengths. Kau cim and the I Ching compared sets them side by side, and the broader survey of Chinese divination methods places both against the birth-chart systems.

After the cast

Whatever built it, you now have a hexagram, possibly a second one, and a question. Read the primary hexagram as the matter standing where it is, the changing lines as what is in motion, and the resulting hexagram as where it goes if that motion continues.

Then stop. The classic will keep yielding material for as long as you keep reading, and past the point where the question is answered you have stopped consulting and started negotiating.