ABCD Pattern

The ABCD pattern was first described by H.M. Gartley in "Profits in the Stock Market" (1935) as the basic building block of all harmonic patterns. Gartley observed that price moves in symmetric leg pairs: after an initial impulse (AB), price retraces to a Fibonacci level (BC), and then resumes in the original direction with a leg (CD) that mirrors AB in both price distance and often in time. He called this the "AB=CD" principle and devoted an entire chapter to its application across different market conditions and timeframes.

The core premise is rooted in the Elliott Wave Principle: AB represents an impulse sub-wave, BC is the corrective pullback, and CD is the next impulse sub-wave. When BC retraces AB to a 0.618 Fibonacci level, CD tends to equal AB in length, creating a symmetric pattern.Scott Carney later formalised this within his harmonic trading framework, adding the alternative ABCD where BC retraces to 0.786 and CD extends to 1.618. The ABCD pattern appears at all degrees of trend, from 1-minute tick charts to monthly bars.

The ABCD is unique because it relies on a single Fib ratio at C rather than a multi-level PRZ. This makes it both simpler to identify and more prone to failure without confluence. The pattern appears constantly across all timeframes as a natural rhythm of price expansion and contraction. Gartley believed that the AB=CD symmetry reflected a natural market law: after a sharp move in one direction, traders take profits (BC), and then re-enter in the original direction with equal vigour (CD), creating a mirror image of the initial move.

Time symmetry is an optional but powerful filter: when the number of bars from C to D approximately equals the number of bars from A to B, the pattern has "time symmetry." Gartley emphasised that patterns with both price and time symmetry were significantly more reliable than those with price symmetry alone. Modern harmonic traders consider time symmetry as a strong confirmatory factor but do not require it for entry.

The C retracement level determines the D projection ratio. Each C level corresponds to a specific CD extension because the AB=CD rule enforces that CD = AB in price distance. The following table shows the relationship between C retracement and D projection for the most common configurations.

1. 1
   Set A at a swing low/high

   The start of the first impulsive leg. A should be a clear pivot with preceding trend confirmation. The prior trend should be well-established before A.
2. 2
   Set B at the leg end

   Where the initial impulse terminates. B should be a distinct swing extreme with momentum exhaustion visible. A long upper wick (for bullish ABCD) or lower wick (for bearish) adds confirmation.
3. 3
   Set C at the retracement

   The pullback point. The tool automatically projects D based on the selected C retracement ratio. Drag C to snap to Fib levels. The D projection updates in real time as you move C.

The ABCD pattern is common, but many apparent ABCD formations fail to produce reliable reversals. Use the following criteria to filter for high-probability setups only. Applying these filters can improve win rates from 50% to 70% or higher.

• Clean AB leg: A\u2013B should be a recognisable impulse with little overlap. Choppy AB legs produce unreliable CD projections. The AB leg should have at least 3 bars with a clear trend direction.
• C within 0.382\u20130.886: C must retrace AB within the acceptable range. A C retracement of 0.5 is valid but less reliable than 0.618. Retracements outside the range are invalid.
• CD leg quality: D should be reached in a similarly clean swing to AB. A messy, overlapping CD leg suggests the pattern is failing. The CD leg should have expanding volume and minimal overlap.
• AB=CD proximity: In standard mode, D should be within 2\u20133% of the AB price distance. Larger deviations reduce reliability. Use the tolerance setting to enforce strict AB=CD equality.
• Time symmetry (optional): If time from A\u2013B is 10 bars and C\u2013D is 10 bars, the pattern has time symmetry. A difference of more than 30% reduces pattern quality but does not invalidate it.
• Trend alignment: The ABCD should form in the direction of the larger trend. A bullish ABCD (D is a low) inside a bull trend is higher probability than a bearish ABCD against it.

The ABCD is a reversal pattern traded at the D completion point. The direction of the trade depends on the pattern orientation: a downward ABC with CD extending down creates a bearish ABCD (D = continuation lower), while an upward ABC with CD extending up creates a bullish ABCD (D = continuation higher). The trade is entered at D in the direction of the prior AB leg.

Knowing when an ABCD pattern has failed is critical for risk management. The following conditions indicate that the trade should be exited or not entered at all.

• CD overshoots: If CD extends beyond 1.618 of BC without reversing, the pattern has failed. Exit any existing position or cancel pending entry orders. The extended CD may be the start of a Three Drives pattern.
• C exceeds A: If C retraces past A (e.g. C > A in an uptrend), the AB impulse has been fully retraced \u2014 the pattern is invalid. The structure may be a trend reversal rather than a pullback.
• D slices through: Price reaches D intraday but closes beyond it and continues. The CD leg has momentum, and the reversal zone has failed. Do not re-enter \u2014 the pattern is dead.
• AB=CD mismatch: In standard mode, if CD is significantly shorter or longer than AB (over 5% deviation with tight tolerance), the symmetry principle is violated. Re-check the C retracement level.
• Trend reversal damaging the setup: If the larger trend reverses while the ABCD is forming, the pattern must be re-evaluated in the new trend context. A pattern that was valid in a bull trend may be invalid in a newly established bear trend.
• Low volume CD leg: If CD forms on declining volume while AB formed on expanding volume, the move lacks institutional support. These patterns have a high failure rate at D.

The ABCD pattern is both a standalone tool and a component of larger harmonic patterns. In the XABCD family, the AB\u2013BC\u2013CD structure forms inside the X\u2013A leg. A valid ABCD within the XA leg can provide an early entry signal before the main D completion point is reached. The key difference: ABCD uses AB as its reference leg, while XABCD uses XA as the primary projection leg for the D completion point.

• Standalone ABCD: trade at D with target at B or A. The AB=CD rule is the only projection method.
• ABCD inside XA leg of XABCD: trade the small ABCD first (early entry for scalpers), then the larger XABCD on confirmation at the main PRZ.
• If the small ABCD fails (D overshoots), the larger XABCD may still be valid \u2014 do not conflate the two patterns. Each has its own PRZ and invalidation conditions.
• ABCD patterns can also nest: a larger ABCD may contain a smaller ABCD within the AB leg, creating a fractal harmonic structure.

The ABCD pattern captures a pure cycle of trend and retracement that reflects the natural rhythm of market participation. The AB leg represents an initial burst of buying or selling conviction, driven by news, earnings, or technical breakouts. The BC retracement reflects profit-taking and uncertainty \u2014 early winners exit, and doubters question whether the move was genuine. The CD leg represents the resumption of the original move with renewed conviction, often driven by latecomers who missed the AB leg and are now "buying the pullback." The completion at D occurs when this second wave of buying/selling exhausts itself, often at the point where the AB=CD equality is satisfied.

Gartley believed that the AB=CD rule worked because it reflected a natural "echo" in price action: the second impulse (CD) tends to equal the first (AB) because the same group of traders drives both moves. The first move catches them off guard, the retracement gives them time to analyse, and the second move is their delayed participation. When the CD leg exhausts at the AB=CD level, the pattern completes and a correction begins. This rhythm of surprise, analysis, and delayed action is deeply rooted in human trading psychology and appears across all markets and timeframes.

ABCD patterns operate across all degrees of trend, from 1-minute tick charts to monthly bars. A key advantage of the ABCD pattern is that it can be used to identify entry points within larger harmonic structures. For example, a daily XABCD pattern may contain a smaller 4-hour ABCD within the XA leg. Trading the smaller ABCD provides an early entry for the larger pattern. This fractal property means that ABCD patterns can be stacked \u2014 a larger ABCD contains smaller ABCDs within each leg \u2014 creating opportunities at multiple degrees. Always verify the higher timeframe trend direction before trading a lower timeframe ABCD.

The ABCD pattern\u2019s win rate depends heavily on the C retracement level. Historical backtests across major markets show that patterns with C at exactly 0.618 have a win rate of approximately 65\u201370%, while patterns with C at 0.382 or 0.886 have win rates closer to 50\u201355%. This makes the 0.618 retracement the sweet spot for ABCD trading. The average risk/reward ratio for a standard ABCD (C=0.618, D=1.272) is approximately 1:2.2 when targeting the B level. The alternate ABCD (C=0.786, D=1.618) produces a higher risk/reward (approximately 1:3.5) but with a lower win rate (55\u201360%).

Time symmetry significantly improves performance. Patterns where the time from C to D is within 20% of the time from A to B have a win rate approximately 10 percentage points higher than patterns without time symmetry. The pattern performs best on daily and 4-hour charts where market structure is cleanest. On lower timeframes, the AB=CD rule generates excessive noise and false signals. For optimal results, use the ABCD pattern only when the AB leg has at least 5 bars, the C retracement is within 10% of 0.618, and the resulting risk/reward ratio is at least 1:2.

Algorithmic ABCD detection should use dynamic tolerance based on market volatility: tighter tolerance (2%) in low-volatility conditions, wider tolerance (5%) in high-volatility conditions. The C retracement validation should check not only the price level but also the internal structure (3-wave or 5-wave) to avoid false positives. The AB=CD rule should be enforced with configurable precision (default 3% of AB distance). The algorithm should reject patterns where the CD leg takes more than 3x the time of the AB leg, as this suggests the pattern is forming across different market regimes. Filters for minimum bar count (at least 5 bars per leg) and maximum pattern duration (to avoid stale patterns) should be configurable by the user.

Consider a daily chart of EUR/USD where a clear uptrend is underway. Price moves from A (1.0800) to B (1.1000), establishing the initial 200-pip impulse leg. Price then retraces to C (1.0924), a 0.618 retracement of AB (76 pips from B). The tool projects D at 1.1088 (using the standard 1.272 extension of BC). Price reaches 1.1088 exactly three days later with a bearish engulfing candle. A short entry at D yields a target of 1.1000 (the B level, 88 pips profit) and a stop at 1.1138 (50 pips above D, half the AB range). The risk/reward ratio is 1:1.76. The pattern completes when price reaches the B level two days later. This example assumes all criteria are met: clean AB leg, C at exactly 0.618, D at the AB=CD level with a reversal candle.

• 1.Profits in the Stock Market — H.M. Gartley (1935)
• 2.Harmonic Trading Volume 1 — Scott Carney
• 3.ABCD Pattern — Investopedia
• 4.Chart Patterns — ABCD — StockCharts ChartSchool
• 5.Elliott Wave Principle — Frost & Prechter
• 6.Technical Analysis of Financial Markets — John J. Murphy