AB=CD pattern — leg symmetry and the 0.618/1.272 levels

The AB=CD pattern is the simplest building block from which more complex harmonic formations are built. Its essence is symmetry: two price legs of similar length and duration, joined by a correction in the middle. That sounds trivial, but the strict measurement of this symmetry separates a real setup from lines drawn in after the fact. Below I explain how to recognise it and trade it without bending the proportions.

What the AB=CD pattern is

AB=CD is a four-point harmonic formation labelled A, B, C and D, joined by three legs. The A-B leg is the first clear move, the B-C leg is a correction against it, and the C-D leg is a second move in the direction of A-B. The name comes from the key assumption: C-D should be roughly equal to A-B, so the two arms are symmetric in distance and, ideally, in duration. Point D, where the symmetry completes, is the potential reversal zone and the place to enter.

The pattern was popularised by Larry Pesavento and Scott Carney, who combined the old observation about equal legs with precise Fibonacci measurement. If you are starting out, work through the basics of trading harmonic patterns first — AB=CD is their common denominator.

Structure and Fibonacci levels

"Harmonic patterns utilise Fibonacci ratios to identify precise turning points that represent some of the most reliable opportunities in the market." — Scott M. Carney, Harmonic Trading, Volume One, Pearson, 2010

The formation is best read leg by leg. The A-B leg sets the base distance and becomes the reference for what follows. The B-C leg corrects against it and, in the classic measured view, reaches 0.618 of A-B; 0.786 is sometimes acceptable, but a deeper correction suggests a different pattern, such as the Bat. The final leg, C-D, carries price back toward A-B and ends at point D.

The setup's strength comes from the convergence of two measurements near point D. The first is symmetry: C-D should be roughly the same length as A-B. The second is a Fibonacci projection: the C-D leg is often a 1.272 (sometimes 1.618) extension of the B-C leg. When both land close together, they form a narrow completion zone rather than a single point — the potential reversal area. You map it with the same Fibonacci extensions used for targets. The pattern comes in a bullish version (A high, B low, the entry at D opens a long) and a bearish one, its mirror image.

How to recognise the formation step by step

Step 1 — define the A-B leg

Begin with a clear, impulsive move that becomes the A-B leg. It sets the base distance, so choose distinct turning points rather than small jerks inside a consolidation.

Step 2 — measure the B-C correction

Apply the Fibonacci tool to the A-B leg and check where the B-C correction ends. In a measured AB=CD you want a retracement around 0.618, at most 0.786. If it is shallower or much deeper, it is probably a different pattern — do not bend the proportions.

Step 3 — locate point D from two measurements

Calculate two things at once. First, project the A-B distance from point C — that gives the symmetric C-D. Second, check where the 1.272 extension of the B-C leg falls. Where they meet is point D.

Entry, stop and targets — a hypothetical example

Let us return to the setup in the table above. Once price reaches the D zone (1.0725–1.0765), you do not open a position at the Fibonacci level itself — wait for confirmation: a reversal candle, a hammer or a bullish engulfing inside the zone. The stop loss goes just below the lower edge of the zone, around 1.0705: once the market clearly breaks the completion, the formation's logic no longer holds.

You set targets on retracements of the whole A-to-D move: the first take profit is 38.2 percent of the A-D leg, around 1.0840, the second about 61.8 percent, near 1.0900. With risk of a few dozen pips, a realistic risk-to-reward ratio usually sits around one to two. To be clear: these numbers are illustrative only and show the reasoning, not a forecast.

The most common mistakes when trading AB=CD

1. Accepting a B-C correction clearly deeper than 0.786 of A-B — that is the signature of a different pattern, such as the Bat, not a measured AB=CD.
2. Treating the 1.272 extension alone as sufficient — without matching the C-D length to A-B you lose the formation's most important filter.
3. Overlooking time symmetry, when the C-D leg is much shorter or longer in time than A-B — the price proportions can then mislead.
4. Entering before point D completes, while the C-D leg is still unfolding — that means jumping into a move that may keep extending the correction.
5. Setting the stop too tight at point D — the completion zone is often tested by wicks, so the stop belongs beyond the zone, not inside it.

How AB=CD differs from five-point patterns

The most important difference is structural: AB=CD has four points, while patterns such as the Gartley, Bat or Crab have five (X-A-B-C-D). The extra X-A leg gives them a different reference — point D is measured against the XA leg, not the leg symmetry. It then lands on a 0.786 retracement of XA in the Gartley pattern, a deeper 0.886 in the Bat pattern and a 1.618 extension in the Crab pattern (the guide to Gartley and Bat patterns breaks those down).

Crucially, each of these five-point formations contains an AB=CD structure inside it — which is why I call it the foundation. Master its symmetry and measurement and you will read the complex patterns faster. Fluent reading of ordinary Fibonacci retracements is a prerequisite — without it, the measurements are guesswork.

Who this formation is for

AB=CD is often called a "beginner" pattern, and there is some truth to that: it has the fewest points and the simplest logic. That does not make it easy to trade live, though — it is tempting to assume the symmetry "almost" fits and enter too early. It is a supporting tool, not a standalone system: it works best with trend context, support and resistance, and candle confirmation. Before you use it live, master technical analysis fundamentals and practise on history.

What to do tomorrow to learn the AB=CD pattern

1. Open TradingView on EUR/USD on the hourly timeframe and review recent clear, two-leg moves, marking points A-B-C in turn — this trains you to see the formation's context before a tradeable D-zone entry appears on the chart.
2. On each candidate, measure two things at once with the Fibonacci tool: whether the B-C correction sits around 0.618 of A-B, and whether the 1.272 extension of the B-C leg coincides with the level where C-D matches A-B.
3. Set up a simple spreadsheet journal with columns for the leg proportions, the boundaries of the D zone, the stop-loss level and the achieved risk-to-reward ratio, then fill it in after every demo trade to see your results in numbers.
4. Place a price alert at the C-D symmetry completion level of the pair you are watching, instead of staring at the chart for hours — when price reaches the D zone you can calmly judge whether a reversal candle confirms the entry.
5. Take at least twenty demo trades on the measured AB=CD pattern alone and document each one with its outcome — only repeatable performance justifies moving the pattern to a live account alongside more complex harmonic formations.