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

Three methods, one output. Here's exactly how to generate a hexagram — with the math behind each approach.

Casting the I Ching means generating six lines, one at a time, from bottom to top. Each line is either solid (yang) or broken (yin). Some lines are "changing" — they're about to flip to their opposite. You need a randomizing process to produce these lines, and there are three commonly used methods: yarrow stalks, three coins, and digital tools.

The method matters less than you might think. All three produce the same output format — a hexagram with possible changing lines. The differences are practical (speed, convenience) and mathematical (slightly different probability distributions). Let's walk through each one.

The three-coin method

This is the most common method used today. You need three coins and a pen and paper to record the lines.

Assignment: One side of the coin = 3 (traditionally heads). Other side = 2 (traditionally tails).

Procedure:

1. Hold the coins and think about your question.
2. Toss all three coins simultaneously.
3. Add the values. The sum will be 6, 7, 8, or 9.
4. Record the corresponding line (see below).
5. Repeat five more times, building the hexagram from bottom to top (line 1 through line 6).

If you got no changing lines (all 7s and 8s), read the hexagram text only. If you got one or more changing lines, read the hexagram text, the specific changing line texts, and then the "relating hexagram" formed by flipping all changing lines.

The yarrow stalk method

This is the oldest documented casting method, described in the Xici Zhuan (繫辭傳, "Great Treatise"), one of the Ten Wings. It uses 50 stalks of the yarrow plant (Achillea millefolium), though one stalk is set aside and never used, leaving 49.

Procedure (abbreviated):

1. Take 49 stalks. Divide them randomly into two piles.
2. Remove one stalk from the right pile and place it between your little finger and ring finger.
3. Count off the left pile in groups of 4. Place the remainder (1–4 stalks) between ring and middle finger.
4. Count off the right pile in groups of 4. Place the remainder between middle and index finger.
5. You now hold 5 or 9 stalks. Set them aside. Combine the remaining stalks (40 or 44).
6. Repeat the divide-and-count process twice more on the remaining stalks.
7. After three operations, you'll have a pile of 24, 28, 32, or 36 stalks. Divide by 4 to get the line value: 6, 7, 8, or 9.

This takes about 15–20 minutes for a full six-line hexagram. The yarrow method produces different probabilities than the coin method:

The yarrow method gives changing yang lines more often (18.75% vs 12.5%) and changing yin lines less often (6.25% vs 12.5%). Whether this matters is debated. Stephen Karcher, in Total I Ching (2003), argues the yarrow probabilities better reflect the I Ching's philosophy — stable yin is the most common state, and dynamic yang change is more frequent than dynamic yin change. Most practitioners use whichever method they have time for.

Online casting tools

Several websites and apps generate I Ching hexagrams. Good digital casters simulate either the coin or yarrow probabilities, show you the hexagram visually, and provide the text. Some let you choose which probability model to use.

The practical question is whether clicking a button feels different from physically casting coins or sorting stalks. Many practitioners find the physical ritual valuable — not because it's supernaturally necessary, but because it forces you to slow down and frame your question carefully. The 15 minutes spent on yarrow stalks is a form of meditation before the reading. That said, if you're traveling or don't have materials, an online caster will give you a valid hexagram.

How to frame your question

The I Ching responds to the question you ask. Vague questions produce vague readings. Here's what works:

• Be specific about the situation. "Should I take the job offer from Company X?" is better than "What about my career?"
• Avoid yes/no framing when possible. The I Ching describes situations and tendencies, not binary outcomes. "What do I need to understand about this relationship?" works better than "Will we get back together?"
• Focus on your own actions. "What should I do about X?" is more productive than "What is X going to do?" The book consistently addresses the querent's choices, not other people's behavior.
• Write it down. Before casting, write the question on paper. This forces precision and creates a record you can revisit later.

Reading the result

Once you have your hexagram, the reading order is:

1. Read the hexagram statement (卦辭) — the overall judgment for this hexagram.
2. Read the Image (象辭) — the traditional commentary, usually describing the trigram image.
3. If you have changing lines, read only the changing line texts (not all six). If multiple lines are changing, read all of them, with priority to the lowest-numbered.
4. Read the relating hexagram — the hexagram formed by flipping all changing lines. This shows the direction the situation is heading.

Hellmut Wilhelm, in Change: Eight Lectures on the I Ching (1960), describes this as reading the "present hexagram" for the current situation and the "future hexagram" for where things are moving. If you have no changing lines, the situation is stable — what you see is what you have.

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