Guide
I Ching coins
Which side is heads, what the numbers mean, and the one thing you have to decide before you start. You can do all of this with three ordinary coins from your pocket.
What the coins actually are
Traditional I Ching casting uses Chinese cash coins — the round bronze coins with a square hole in the middle, minted for roughly two thousand years. A set is usually five or six coins, but the three-coin method needs exactly three. The extras are for yarrow-style counting and for having a spare.
They are not magical objects, and nothing in the method depends on them being old. The coins are a randomiser. What makes the cast meaningful is the structure it produces, not the metal.
Do you need special coins?
No. Any three coins with two sides you can tell apart will work — dimes, quarters, a foreign currency you have left over from a trip. Yarrow stalks are the older method and produce slightly different odds; the coins are the simplification, and the one most people actually use.
A dedicated set is worth owning for one reason only: it stops you improvising. When the same three coins live in the same small pouch, casting stops being a decision you make and becomes a habit you keep.
Which side is heads? The question everyone asks
This is the single most common question about the coin method, and the honest answer is that it is a convention, not a fact. There is no universally correct side. What matters is that you fix the rule once and never change it in the middle of a cast.
The most common convention assigns 3 to the yang side and 2 to the yin side. On a Chinese cash coin, the inscribed face — the one with the Chinese characters — is usually taken as yang, and the plainer reverse side as yin. With Western coins the same convention is normally written as heads = 3, tails = 2.
Pick one and write it down. If you flip the assignment, the throws still land with exactly the same probabilities — but three heads now produces 6 instead of 9, so which physical outcome gives you a moving line changes. Decide before the first throw, not after an answer you dislike.
The four possible throws
Three coins, each worth 2 or 3, so the sum is always one of four values. This table is the whole method:
| Coins | Sum & meaning |
|---|---|
| three tails (2+2+2) | 6 — a changing broken line, old yin. Odds 1 in 8. |
| two tails, one head (2+2+3) | 7 — a stable solid line, young yang. Odds 3 in 8. |
| one tail, two heads (2+3+3) | 8 — a stable broken line, young yin. Odds 3 in 8. |
| three heads (3+3+3) | 9 — a changing solid line, old yang. Odds 1 in 8. |
Notice that 7 and 8 are three times as likely as 6 and 9. That asymmetry is not a flaw — it is why the method feels the way it does. Most lines are stable; movement is the exception, which is what gives a changing line its weight.
A worked example
Six throws, recorded from the bottom line upwards. Tails count 2, heads count 3.
| Throw 1 | tails · tails · heads = 7 — stable solid line (young yang) |
|---|---|
| Throw 2 | tails · heads · heads = 8 — stable broken line (young yin) |
| Throw 3 | tails · tails · tails = 6 — changing broken line (old yin) moving |
| Throw 4 | tails · tails · heads = 7 — stable solid line (young yang) |
| Throw 5 | tails · heads · heads = 8 — stable broken line (young yin) |
| Throw 6 | heads · heads · heads = 9 — changing solid line (old yang) moving |
Turn each value into a line: 7 and 9 are solid, 8 and 6 are broken. Written from the bottom up that gives:
That is Biting Through (Shì Kè), hexagram number 21. Lines 3, 6 are changing, so they flip: line 3 turns from broken to solid and line 6 turns from solid to broken. The result is a second hexagram:
Read it in three passes. Biting Through is the situation you are actually in. The changing lines are the specific instruction. Abundance is where it is heading if you follow it.
Read hexagram 21 → Read hexagram 55
Why 6 and 9 are the ones that move
6 is a broken line that has been broken as long as it can be; 9 is a solid line that has been solid as long as it can be. Both sit at the end of their run, so they are the ones with somewhere to go. 7 and 8 are young lines, still in progress, and they stay put.
If no line moves, the reading is simply the hexagram you got. With three coins that happens reasonably often — the chance that all six lines are stable is about 18%, so roughly four casts in five will carry at least one moving line.
Coins, yarrow stalks, or dice?
| Method | Odds and character |
|---|---|
| Three coins | 6 and 9 at 1 in 8 each. Even split between the two kinds of movement. Fast, and what most people use. |
| Yarrow stalks | 6 at 1 in 16, 9 at 3 in 16. Slower and more ceremonial; yang changes are three times as common as yin changes. |
| Dice | Fine as a randomiser, but only if you reproduce the distribution rather than rolling for a hexagram. One d8 works for the coins: put 6 on one face, 9 on one face, and 7 and 8 on three faces each. Giving all four numbers two faces each is not equivalent — that makes every value equally likely, which is a different oracle from both of the methods above. |
Here is the detail almost every explanation gets wrong. Both methods produce a moving line one time in four — that rate is the same. What differs is the flavour of the movement: coins give you 6 and 9 equally often, while yarrow makes 9 three times as common as 6. So yarrow leans towards yang turning, and coins are even-handed. That is a real difference in how the oracle behaves, and it is why a good online cast has to use the actual numbers rather than picking a hexagram at random.
The mistake almost everyone makes first
Writing the first throw at the top. A hexagram is built from the bottom line upwards, always, and reading order is fixed by the text — line 1 is the foundation and line 6 is the top. Draw the first throw at the base and stack upwards, and you will not have to redo a cast because the whole figure is upside down.
Our full walkthrough of the procedure, including how to phrase the question, is in how to cast the I Ching.