What is the Crab pattern? Origin and ratio rules

The Crab comes from Scott Carney, who coined the term harmonic trading and dates the pattern to 2000. He treats the 1.618 extension of XA as the defining level of its PRZ and pairs it with an extreme projection of the BC leg. As with every harmonic pattern, sources publish slightly different ranges; the ones below are the common version, applied with a small tolerance.

Like the Butterfly, the Crab is an extension pattern: D completes beyond X. The difference is distance. The Butterfly’s D sits 0.27 of XA past X; the Crab’s sits 0.618 of XA past it, and the pattern usually starts from a shallower B.

  • XA: the first swing. In a bullish Crab, X is a low and A a high; in a bearish one, the reverse.
  • B: a 0.382–0.618 retracement of XA. A B at 0.886 makes it a Deep Crab; a B near 0.786 points to a Butterfly instead.
  • C: a 0.382–0.886 retracement of AB.
  • D: a 1.618 extension of XA. This is the level that matters most.
  • BC projection: CD measures 2.24, 2.618, 3.14 or 3.618 times BC; use whichever lands closest to 1.618 XA.
  • AB=CD: CD is longer than AB, often 1.27 or 1.618 times it and sometimes more. Carney calls it the least important level in the Crab’s PRZ.

The Deep Crab: B at 0.886

Carney describes a variation he dates to 2001, the Deep Crab, in Harmonic Trading: Volume One (2010). Everything is the same except B, which retraces 0.886 of XA, close to X. D still completes at the 1.618 extension of XA, as the drawing below shows.

Because B sits so close to X, the CD leg of a Deep Crab often breaks B and then X on its way down, which looks like a breakdown to most traders. That is the move the pattern expects to fade, but only at 1.618 and only after a reversal candle. With X at $100.00 and A at $120.00, a Deep Crab’s B would sit near $102.28 ($120.00 − 0.886 × $20.00), and D would still be at $87.64.

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Two lettered zigzags on the same scale, each with a dashed line at the X level and dotted lines at the 1.27 and 1.618 extensions: on the left, a Crab with B = 0.382–0.618 XA and D circled on the 1.618 line (D = 1.618 XA); on the right, a Deep Crab whose B sits just above the X line (B = 0.886 XA), with D also circled on the 1.618 line and the note price often breaks B and X on the way to D.

Why the move into D is fast, and the reversal sharp

The CD leg of a Crab is the longest leg in the classic family: 2.24 to 3.618 times BC, and in the example below more than twice the length of AB. To get there, price has to break X and then the 1.27 extension, two levels where buyers from other patterns often wait. Each break can trigger stops and attract momentum sellers, so the last part of the move tends to come in wide, fast candles.

One common explanation for the sharp turns is that by the time price reaches 1.618, many sellers have already sold and the stops below the old lows have been taken; when selling dries up, short sellers buying back can add fuel. That describes what traders often see; it is not a law. The same speed works against you: a fast move can slice through the PRZ, a resting limit order can fill in the middle of a falling candle, and a stop can fill below its price.

The practical consequences: don’t buy X or the 1.27 level along the way, prepare the PRZ in advance, and wait for the candle to close. Signs of slowing at D, such as smaller candles, long lower wicks or RSI divergence, add weight; they do not replace the close.

Deep Crab
A Crab whose B retraces 0.886 of XA instead of 0.382–0.618. D still completes at 1.618 of XA.
1.618 XA extension
The level 1.618 times XA away from A, which is 0.618 of XA beyond X. With X at $100 and A at $120, it sits at $87.64.
Extreme BC projection
A CD leg 2.24 to 3.618 times as long as BC. The Crab is the classic pattern whose last leg is this long.

How to build the Crab PRZ

As in every harmonic pattern, the PRZ is a cluster, not a single price. For a bullish Crab, compute these levels below C and keep the tightest group around 1.618 XA. The drawing below shows the cluster from the example in the next section, with the levels price falls through on the way.

  1. XA extension: D = A − 1.618 × XA. This is the anchor.
  2. BC projections: D = C − 2.24, 2.618, 3.14 and 3.618 × BC. Keep the one closest to the anchor.
  3. AB=CD: D = C − 1.27, 1.618 or 2.24 × AB. Keep the one closest to the anchor.
  4. The PRZ runs from the nearest to the farthest of the levels you kept. If it is wide compared with XA, or the levels disagree, skip the pattern.
  5. Mark X and the 1.27 XA extension too, as levels price will pass through: they are warnings, not entries.

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A price ladder: a column of large red candles falls through a dashed line at X 100.00 and dotted lines at 1.27 XA 94.60 and 3.14 BC 91.89, noted passed through: not entries, into a yellow band where three lines meet, 3.618 BC 88.37, 1.618 XA 87.64 and 2.24 AB=CD 87.31, noted three measurements meet; a final green candle with a long lower wick closes back above the band, and a red dashed stop line runs at 86.60.

Crab pattern example: measuring a bullish Crab

A hypothetical 1-hour chart of a stock, shaped like the drawing at the top of the page. X is a swing low at $100.00 and A a swing high at $120.00:

  • XA = $120.00 − $100.00 = $20.00.
  • B = $120.00 − 0.618 × $20.00 = $107.64, so AB = $12.36.
  • C = $115.00: BC = $7.36, and $7.36 ÷ $12.36 = 0.595 of AB, inside 0.382–0.886.
  • 1.618 XA: $120.00 − $32.36 = $87.64, which is $12.36 below X.
  • BC projections: 2.24 × $7.36 puts D at $98.51, 2.618 at $95.73, 3.14 at $91.89 and 3.618 at $88.37. The last is closest to the anchor.
  • AB=CD: 1.618 × $12.36 puts D at $95.00, and 2.24 × $12.36 at $87.31. Keep $87.31.
  • PRZ: $87.31 to $88.37, around the 1.618 XA level at $87.64. X ($100.00) and the 1.27 XA extension ($94.60) lie on the way: levels to watch, not to buy.

Trading the example: entry, stop, targets and size

Price drops from $115.00 in a string of wide red candles, through $100.00 and $94.60, and trades down to $87.50 inside the zone. The next 1-hour candle closes at $88.90 with a long lower wick, back above the PRZ. You buy at $88.90.

Carney writes that the Crab calls for a very small stop, and the logic is the same as in the Butterfly: X, at $100.00, is far above the entry. The stop goes below the PRZ: $87.31 minus half of a hypothetical 1-hour ATR of $1.40 gives $86.60, or $2.30 of risk per share. Risking 1% of a $20,000 account ($200) allows 86 shares ($200 ÷ $2.30).

Targets: the usual 0.382 and 0.618 retracements of AD. AD = $120.00 − $87.50 = $32.50, so the targets are $99.92 and $107.59, close to X and to B. On paper the first pays about 4.8R. That number comes from a long leg and a tight stop, not from any probability, and the levels price broke on the way down can act as resistance on the way back up. A nearer checkpoint at the 1.27 level ($94.60, about 2.5R) is where many traders take something off and move the stop to breakeven; see stop loss and take profit and trailing stops.

If a candle closes below $86.60 instead, the trade is over: about $198 lost (86 × $2.30), as planned. Don’t widen the stop to give it room; the pattern’s logic ends at the PRZ.

How to draw a Crab on TradingView

Use the XABCD Pattern tool, in the Patterns group of the drawing toolbar on the left of the chart; TradingView has no separate Crab tool, and its help page lists the Crab among the common patterns the XABCD tool is meant for.

  1. Select XABCD Pattern and click X, A, B and C on completed swings. Check that B reads 0.382–0.618 (or 0.886 for a Deep Crab) and C 0.382–0.886.
  2. Drag the Fib retracement tool across XA with 0 at A and 1 at X; the 1.618 level, beyond X, is your anchor.
  3. Drag a second Fib retracement across BC with 0 at C and 1 at B, and add 2.24, 3.14 and 3.618 as custom levels if they are missing: they mark the BC projections.
  4. Mark the AB=CD levels, draw a rectangle over the cluster and place D inside it. Add horizontal lines at X and at 1.27 XA, labeled as levels to watch rather than entries.
  5. Set an alert at the top of the PRZ with TradingView alerts so you don’t chase the fast leg, then wait for a candle to close. Rehearse on old charts with bar replay.

Common Crab mistakes, and what a failure looks like

A failed Crab usually looks like the setup until the last moment. Same hypothetical pattern: the candle closes at $88.90 and you buy, then a market-wide sell-off pushes price through $86.60 to $84.00 in two candles. In the fast market the stop fills a little below its price, and the loss is a bit over $200. That is the cost of trading a fast pattern, and why position size matters more than the entry.

The mistakes that make it worse:

  • Buying at X or at 1.27 because “it has already fallen a lot”. In a Crab, those levels are on the way, not the destination.
  • Putting the stop below X. X is far above the entry, so a stop there makes no sense.
  • Resting a blind limit order at 1.618 in a fast market. Price can trade through it before any buyer appears.
  • Calling a 0.786 B a Crab. That is a Butterfly candidate, with D at 1.27, not 1.618.
  • Accepting a wide PRZ. If the BC projection and the AB=CD land far from 1.618 XA, there is no cluster.
  • Trading through news. A drop driven by earnings or a macro shock can ignore every ratio; check the economic calendar and the higher timeframe with multi-timeframe analysis.
  • Skipping the record. Log every Crab you draw in advance, filled or not, in a trading journal; otherwise you remember the sharp reversals and forget the failures. Trading expectancy explains why both count.

Crab vs Butterfly

Both are extension patterns: D completes beyond X, and the stop goes beyond the PRZ, not beyond X. The drawing below compares them on the same scale; the Butterfly pattern lesson covers its rules and examples in detail.

In practice, start with B: a 0.786 B means Butterfly; 0.382–0.618 (or 0.886) means Crab. Then check how far the last leg must run. The Crab’s longer, faster CD leg makes its PRZ harder to buy calmly, one more reason to plan the entry and the size before price arrives. For confirmation and trade management at the zone, see trading the PRZ.

  • B: 0.382–0.618 of XA (0.886 in the Deep Crab) vs 0.786 in the Butterfly.
  • D: 1.618 of XA vs 1.27 (up to 1.618 in some rule sets).
  • CD: 2.24–3.618 times BC vs 1.618–2.24.
  • Speed: the Crab’s last leg is usually the faster one, so plan for slippage.

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Two lettered zigzags on the same scale, each with a dashed line at the X level and dotted lines at the 1.27 and 1.618 extensions: on the left, a Butterfly whose D is circled on the 1.27 line, with B = 0.786 XA, D = 1.27 XA and CD = 1.618–2.24 BC; on the right, a Crab whose D is circled on the 1.618 line, with B = 0.382–0.618 XA, D = 1.618 XA and CD = 2.24–3.618 BC.